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Insect, Pest and Disease Management in Rice

January 2020

In book: Rice Production Knowledge and Practices for Ensuring Food Security
Publisher: Austin publishing group

Authors:

Introduction Insect, pest and disease management is vital in attaining sustainable rice production. Rice serves as a staple diet for about half of the world’s population and it is cultivated in 110 countries of the world, covering about one-fifth of world’s cropland under cereals. But its production is affected largely by insects, pests and disease attacks. Reduction in rice yield due to insects, pests, and diseases is recorded to be about 21 % in North and Central America and about 31.5% in Asia (excluding mainland China). Yield loss varies within production conditions. In utter terms, yield losses of about 1.2 to 2.2 tons/ha have been recorded due to weed, insect, pest and disease injuries in Asia. More than 800 rice insect’s species have been reported in the worldwide ecosystems. From these, about 700 species did not cause damage to rice and are considered friendly insects while about 100 species attack rice. Almost 20 insects act as rice pests that include defoliators, stem borers, gall midge and vectors like planthoppers and leafhoppers that cause direct damages and also transmit several diseases at different growth stages (Table 7-1). Management practices are needed to control the loss carried out by different diseases and insects and pests. Most common practices include agronomic practices, biological and chemical control. Agronomic practices include; growing of resistant and early maturing varieties, early sowing of seeds, proper/close plant spacing, avoiding rice hotspot areas of viruses especially of grassy stunt virus and tungro virus, crop and field sanitation/hygiene, ploughing after harvesting that helps to bring eggs to soil surface and abolish them, judicious use of fertilizers, flooding of fields in order to save irrigated crops and after forecasting etc. For biological control of insects and pests, numerous natural enemies (predators, parasites, pathogens, and microbial insecticides) of insects and pests are used. These living entities attack insects and pests and destroy them. A wide variety of insecticide and pesticides are used as chemical control, according to the extent of attack and crop growth stages. Several viral, bacterial and fungal diseases have been noticed. Disease damage can greatly affect growth and yield of rice crops and can sometimes completely destroy the crop. It is observed that destructive viral diseases are not present in any of the rice-growing regions of the world, but fungal and bacterial diseases are widely spread and are very destructive. Some effects of diseases as direct losses include the spotted kernels, low number of grains, lodging, reduction in plant stands and a general plant efficiency reduction while indirect losses include the application costs of fungicides used to control the disease, yield reduction along with special agronomic practices that not only decrease the disease effect but may not be conducive to higher yield production. Diseases and their causal agents are listed in Table 7-2. The physiological disorders such as zinc deficiency, straight ahead, salt damage, cold injury and nutrient deficiencies are sometimes misunderstood as disease symptoms. Management is necessary in order to avoid damage caused by the diseases. Toward disease management, the first step is the identification of disease followed by field scouting so that extent of disease can be determined. Determination of varietal resistance to diseases can be helpful in determining the chances of having problems warranting preventive management measures.

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Insect, Pest and Disease

Management in Rice

Shazia Iqbal

Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad, 38000, Pakistan

Corresponding Author:

Shazia Iqbal, Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad,

38000, Pakistan,

shaziaiqbal91@yahoo.com

Published Date: January 18, 2020

Abbreviations: D: days; DT: Days After Transplanting; Wk: Week; H: Hrs; %: Percent; Sp: Specie; @: At The Rate Of; Ha:

Hectare; Kg: Kilo; Gram; Ml: Milli Liter; Ipm: Integrated Pest Management; Sq.M: Square Meter; E.G: For Example; 2.4.D: 2,4-

Dichlorophenoxyacetic acid; Bt: Bacillus thuringiensis

1. Introduction

Insect, pest and disease management is vital in attaining sustainable rice production. Rice serves as a staple diet for about half of the

world’s population and it is cultivated in 110 countries of the world, covering about one-fifth of world’s

cropland under cereals. But its production is

affected largely by insects, pests and disease attacks. Reduction in rice yield due to insects, pests, and diseases is recorded to be about 21 % in North and

Central America and about 31.5% in Asia (excluding mainland China). Yield loss varies within production conditions. In utter terms, yield losses of

about 1.2 to 2.2 tons/ha have been recorded due to weed, insect, pest and disease injuries in Asia. More than 800 rice insect’s species have been

reported in the worldwide ecosystems. From these, about 700 species did not cause damage to rice and are considered friendly insects while about 100

species attack rice. Almost 20 insects act as rice pests that include defoliators, stem borers, gall midge and vectors like planthoppers and leafhoppers

that cause direct damages and also transmit several diseases at different growth

stages (

Table 7-1

). Management practices are needed to control the

loss carried out by different diseases and insects and

pests. Most common practices include agronomic practices, biological and chemical

control.

Agronomic practices include; growing of resistant and early maturing varieties, early sowing of seeds, proper/ close plant spacing,

avoiding rice hotspot areas of viruses especially of grassy stunt virus and tungro virus, crop and field sanitation/hygiene, ploughing after

harvesting that helps to bring eggs to soil surface and abolish them, judicious use of fertilizers, flooding of fields in order to save irrigated crops and

after forecasting etc. For biological control of insects and

pests, numerous natural enemies (predators, parasites, pathogens, and microbial

insecticides) of insects and pests are used.

These living entities attack insects and pests and destroy them. A wide variety of insecticide and

pesticides are used as

chemical control, according to the extent of attack and crop growth stages.

Several viral, bacterial and fungal diseases have been noticed. Disease damage can greatly affect growth and yield of rice crops and can

sometimes completely destroy the crop. It is observed that destructive viral diseases are not present in any of the rice-growing regions of the world, but

fungal and bacterial diseases are widely spread and are very destructive. Some effects of diseases as direct losses include the spotted kernels, low

number of grains, lodging, reduction in plant stands and a general plant efficiency reduction while indirect losses include the application costs of

fungicides used to control the disease, yield reduction along with special agronomic practices that not only decrease the disease effect but may not be

conducive

to higher yield production. Diseases and their causal agents are listed in

Table 7-1

. The physiological disorders such as

zinc

deficiency, straight ahead, salt damage, cold injury and nutrient deficiencies are sometimes misunderstood as disease symptoms. Management is

necessary in order to avoid damage caused by the diseases. Toward disease management, the first step is the identification of disease followed by

field scouting so that extent of disease can be determined. Determination

Rice Production Knowledge and Practices for Ensuring Food Security

of varietal resistance to diseases can be helpful in determining the chances of having problems warranting preventive

management

measures.

Table. 7-1: Growth stages of rice attacked by insect pests

Growth stages

Insect pests

Vegetative Stage

Seedling maggots

Rice seed midge

Rice caseworms

Rice leaf beetles

Rice gall midge

Grasshoppers, katydids, and field crickets

Rice stem borers

Black bugs

Rice mealybugs

Rice thrips

Rice leaffolders

Mealy bugs

Rice hispa

Armyworms and cutworms

Stalked-eyed flies

Colaspis

Reproductive Stage

Rice Skippers

Leafhoppers

Greenhorned caterpillars

Planthoppers

Lady bird beetle

Ripening stage

Stink bugs

Ripening seed bugs

Rice Chinch bug

Panicle rice mite

Soil Inhabiting pests

Ants

White grubs

Mole crickets

Root aphids

Root-feeding mealybugs

Termites

Field cricket

Root weevil

Wire worm

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Table. 7-2: Rice diseases and their pathogen

Plant growth Stage

Common name

Pathogen name

Cause

Seed and Seedling:

Seedling Blight

Sclerotium rolfsii, Cochliobolus miyabeanus, Fusarium sp.,

Curvularia sp., Athelia rolfsii, Rhizoctonia solani, Athelia rolfsii, and

other pathogenic fungi.

Fungi

Water Mold

Achlyasp. Pythium sp.

Fungi

Roots and Crown

Crown Rot

Erwinia chrysanthemi

Bacteria

Root Rot

P. dissotocum, Fusarium sp., P. spinosum, and Pythium sp.

Fungi

Root Knot

Meloidogyne sp.

Nematode

Leaf Blades:

Rice Blast

Pyricularia oryzae

Fungi

Brown spot

Bipolaris oryzae

Fungi

Narrow brown leaf spot

Cercospora oryzae

Fungi

Leaf smut

Entyloma oryzae

Leaf scald

Sarocladium oryzae

Fungi

Bacterial leaf blight

Xanthomonas campestris pv. oryzae

Bacteria

Stackburn

Alternaria padwickii

Fungi

White leaf streak

Mycovellosiella oryzae

Fungi

White tip

Aphelenchoides besseyi

Nematode

Stem and leaf sheath:

Sheath spot

Rhizoctonia oryzae

Fungi

Sheath blight

Rhizoctonia solani

Fungi

Sheath blotch

Pyrenochaeta oryzae

Fungi

Sheath rot

Sarocladium oryzae

Fungi

Crown sheath rot

Gaeumannomyces graminis

Fungi

Stem Rot

Magnaporthe salvinii

Fungi

Flag leaf collar blast

Pyricularia oryzae

Fungi

Node blast

Pyricularia oryzae

Fungi

Tungro

Rice tungro bacilliform virus (RTBV)

Virus

Grassy stunt

Rice Grassy stunt virus (RGSV)

Virus

Panicle, Florets, and

Grain:

Rotten neck blast

Pyricularia oryzae

Fungi

Head blight

Various fungi

Fungi

Panicle blast

Pyricularia oryzae

Fungi

Bacterial panicle blight

Burkholderia glumae

Bacteria

Downy Mildew

Sclerophthora macrospora

Fungi

Grain spotting or Pecky rice

Fusarium sp., Cochliobolus miyabeanus, Microdochium oryzae,

Sarocladium oryzae, Curvularia sp. and bacteria

Fungi and

Bacteria

Kernel smut

Tilletia barclayana

Fungi

False smut

Ustilaginoidea virens

Fungi

Bakanae

Fusarium moniliforme

Fungi

Black kernel

Curvularia lunata

Fungi

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2. Insect, Pest of Rice and their Management

Stem Borers

Description:

Stem borers are the most severe rice pests in the world. Three families; Noctuidae, Diopsidae, and Pyralidae, have been documented

as rice stem borers. The pyralid borers possess high host specificity. They are most common and

destructive. In Asia, the most destructive and

widely distributed are

Scirpophaga incertulas

Chilo suppressalis

Sesamia inferens, Scirpophaga innotata

, and

Chilo polychrysus

. In Asia,

Chilo suppressalis

and

Scirpophaga incertulas

cause a damage

of 5-10% of the total rice crop.

Scirpophaga incertulas is

distributed in the

temperate and tropics areas. It is the dominant

species in Pakistan, Malaysia, In the Republic of Korea, Bangladesh, Sri Lanka, India, Philippines,

Vietnam, Thailand, and

some parts of Indonesia.

Damage:

The underlying feeding and boring by hatchlings in the leaf sheath cause vast, longitudinal, whitish, stained zones at bolstering

destinations, however just infrequently do they bring about shriveling and drying of the leaf-cutting edges. At

the point in the middle of the vegetative

period of the plant, the focal leaf whorl does not unfurl, but rather turns tanish and gets dry, in spite of the fact that the lower leaves stay green. This

situation is recognized as the dead heart, and the infected

tillers dry off without panicles.

Management

Agronomic Methods:

Crop agronomic practices show an intense effect on the population of stem borer. High rates of

nitrogen fertilizer

will provide more plant nutrition and result in higher yield. However, it also increases the incidence of

bacterial and fungal diseases by increasing

tiller density and tissue susceptibility and boosts the stem borer’s multiplication. Insects generally grow larger and faster, produce more offspring by

completing more generations per crop and cause more damage when high nitrogen is applied. Stem borer moth’s oviposition occurs favorably under

high nitrogen fertilizers. For its management, nitrogen is applied as a split application at optimal rates. Splitting the nitrogen application, and use of

slow nitrogen release forms of fertilizers(e.g. sulfur-coated urea, urea super-granules) helps to attain higher crop yields and lower chances of pest

attack. Silica application helps to increase crop resistance against stem borer. Slag application increases the

silica content and makes it resistant to

stem borer attack.

Clipping the seedlings tip before transplantation is done to eradicate the egg masses. This method is used only for mature seedlings.

Crop harvest at ground level reduces the number of larvae. Harvested crop height is an important factor that determines the larvae percentage,

left in stubble. Removal and destruction of stubbles from rice field, which will help in the destruction of egg masses. To destroy those remaining

eggs, flooding and plowing of fields, and burning

and decomposition of rice stubble are suggested. For decomposition, calcium cyanide is used in

low amount. Plowing and flooding are most effective apparently. Uniform burning of stubble is also difficult in a field. Burning of stubbles is effective

only when larvae migrate to subsurface soils.

In many countries, postponing of sowing and transplanting time is considered a good practice in escaping moth’s first-generation and it

can also decrease the density as well as damage of stem borers both in directly seeded and transplanted rice fields. Changing planting time is not always

effective because of other agronomic attention. In Pakistan, planting date

is scheduled by canal water release only after the emergence of

Scirpophaga incertulas

moths. This late-planted crop is less

affected by moths than early field plantation receiving tubewell irrigation.

Delayed planting is an effective practice against

Scirpophaga incertulas

since emergence is also delayed with planting date. The number of

generations of stem borer is dependent on the crop growth period. Thus, change in planting time has a

slight effect in areas where rice cropping is

practiced continuously.

Light traps are used for collection and destruction of moths. Catching of moths by Light-traps shows a variation from a uni-modal to a bi-modal

pattern in first and second broods. The frequency-vibration-based pest lamps used to kill the stem

borers. They are installed at 200 m distance from

each other in a checkerboard pattern and 1.3–1.5 m above the ground. These lamps are switched on during the light period when immigration of

stem borers occur. However, a disadvantage of these lamps is that it will also cause damage to beneficial insect pests. High insecticidal activities of

Bt rice are observed

against stem borers.

Chemical Methods:

Stem borers are difficult to control with insecticides because larvae are exposed only for a few hours

before they enter the tiller or plant. So when an economic threshold of the dead heart reaches at about 10% in the nursery

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and in the vegetative stage and 1 moth /sq.m. has reached, implementation of the chemical control method is suggested.

Chemicals that are

recommended at these stages are chlorpyriphos, fenitrothion, monocrotophos, cartap hydrochloride, etofenprox, phosalone, endosulfan, fenthion,

phenthoate, and fipronil. Seedlings root dipping in chlorpyriphos (0.02%) for

12-14 h before transplanting gives safety against stem borer for

up to 30 d.

Successful control involves repeated foliar applications. Granular insecticides, particularly diazinon and gamma

BHC, are most effective

than foliar sprays, specifically in high rainfall environments. Gamma BHC is a fumigant that kills

inactive moths. In the dead hearts of young crops,

granules fertigation is effective in preventing stem borer. The insecticide is dissolved partially in the water and is transported between the stem and leaf

sheath by capillary action, to make contact with

young larvae. The limitation in the use of this method is cost and water supply. Granules are costly to

transport. Stable and deep water levels are required for control. A combination of chemo-sterilant and sex attractant (pheromones) also shows

the potential of pest control. Sex pheromone application can decrease the insecticide use by 1–2 sprays, and the input costs

can be decreased than

insecticides.

Biological Methods:

Biological control of stem borers in Africa and tropical Asia mostly comes from native parasites,

predators, and

entomo-pathogens. Over 100 species of these parasitoids have been recognized. The management and

protection of these parasitoids are

essential in the development of successful and stable integrated pest management (IPM)

systems against stem borer. The essential genera

include;

Trichogramma, Telenomus,

and

Tetrastichus, Telenomus

wasps

parasitize stem borer eggs before the eggs are covered by the hair while

the moth is in the oviposition stage. The wasp detects

the female moth, gets attached near ovipositor. Many predators, crickets;

Anaxipha

longipennis,

and

Metioche vittaticollis

, and mirid;

Cyrtorhinus lividipennis

feed on

Chilo suppressalis.

The long-horned grasshopper preys

rapaciously on yellow stem borer eggs. Some important predators are carabid beetles such as

Ophionea

sp., coccinellid beetles;

Micraspis

crocea

and

Harmonia octomaculata

that attack small larvae of stem borers.

Mesovelia vittigera

and

Microvelia douglasi atrolineata

prey on

young larvae when they fall on the water. Ants and many other predators prey on larvae of stem borer.

Several fungal species can attack the larvae and ingest them at the stem base — the

Cordyceps sp.

Fungus feeds on the body of stem

borers. Spiders attack adult moths when resting on foliage. Bats are effective at dusk while birds and dragonflies are active predators at daytime.

Spinetoram, Spinosad,

Empedobacter brevis

and

Beauveria bassiana

possess

greater insecticidal effects on stem borers. Another popular

biological insecticide, Bt agent, is recommended in China to

control rice stem borers.

Armyworms and cutworms

Description:

The hatchlings of a few types of field noctuids are called armyworms and cutworms. They feed extrovertly on

rice plants. They are

comparable in propensities, however, can be comprehensively recognized by the attacking habits. The armyworm hatchlings grow on the over-the-

ground plant's parts, frequently leaving just midribs. The cutworm hatchlings

grow on the underground parts. The common armyworm,

Mythimna

(

Pseudaletia

)

unipuncta

, periodically cause crop losses.

M. unipuncta;

being polyphagous is also a severe pest of wheat, rice, barley, oats, and non-graminaceous crops, cereals, and

grasses. The species is

native to North America, but it is diverse in the allocation and documented throughout Asia, Europe,

and Australia.

Armyworms and cutworms that are described in this chapter are; rice warming caterpillar, fall armyworm, and

common cutworm.

Rice swarming caterpillar

Description:

The rice swarming caterpillar (

Spodoptera mauritia acronyctoides

) infrequently makes substantial losses to

rice crops. A

preferred host of this polyphagous insect is upland rice, but it also infects weeds and graminaceous crops. It is standout amongst the most genuine

creepy crawly bugs in South India and widely distributed in Southeast and East Asia. It

is the most damaging pest of the armyworms in rice

regions of Asia.

Damage:

The swarming caterpillars appear unexpectedly in multitudes and move from field to field. They generally affect the nursery of rice, and

the transplanted crop is not sternly affected by their attack. Newly hatched larvae give the plant a sickly look with cut leaves and withered tips while

older larvae attack and feed wholly and ravenously defoliate the plant.

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Fall armyworm

Description:

The fall armyworm (

Spodoptera frugiperda

) causes economic losses to rice crops though it comes about only

periodically. It is also

known as southern armyworm grass worm and overflow worm. It also attacks cereals, grasses, tobacco, cotton, legumes, and cabbage. It has been

noticed in Central and North America but is common in Central and, southern USA,

and in neotropical areas.

Damage:

The hatchlings feed on leaves, leaving the epidermis undamaged. At first, they eat just delicate parts of leaves, as

they develop they eat up

all foliage, leaving just the hard plant parts. Harm becomes obvious around 3-4 d after the invasion,

and overwhelming defoliation ends up after

the hatchlings assemble on the plants.

Common cutworm

Description:

The common cutworm,

Spodoptera litura

, is also known as tobacco caterpillar or tobacco cutworm, grass

cutworm, and

vegetable cutworm. It is a common polyphagous insect of various agricultural crops. It is found sporadically and causes economic losses to rice,

cabbage, maize, castor, smaller millets, jute, tobacco, sweet potato, and in many other

crops. It is found generally in Pakistan, India, Australia, East

Asia, Turkey, China, and several African countries.

Damage:

The common cutworm needs dry land for pupation, and for causing damage, so it is a problem only on upland rice.

Larvae migrating from

grassy areas adjacent to low land rice usually cause massive damage. Young caterpillars feed on soft

leaves, but fully-grown can consume the whole

plant. Their effect is serious on seedlings where they cause damage at the

base. Fully grown caterpillar severely defoliates the rice crop during

late crop growth.

Management:

Control measures for all cutworms and armyworms are similar.

Agronomic Methods:

Seedbeds should be made away from grasses and weeds areas to avoid cutworms and armyworms

migration to alternate

hosts. Plowing fallow land and weed removal from areas outside the fields helps to control cutworms

and armyworms. Use of resistant rice varieties

is recommended. Several wild kinds of rice have moderate resistance to

Mythimna separate

and

Spodoptera mauritia acronyctoides.

Chemical Methods:

Insecticides; Sevin (@ 0.15 to 0.25%) and Furadan (@ 10 kg/ha) are used to control armyworm and

cutworms. These insecticides are suggested to be applied as sprays because of their effectiveness over granular form.

Since insecticides rapidly break down in high temperature and sunlight. Insecticide spray should be done in the late afternoon to make sure

that larvae are in their resting places because after that larvae climb up the plants. To destroy large cutworm and armyworm larvae, higher doses are

required, because of direct positive linkages between insecticide toxicity

and insect body weight.

Biological Methods:

Cutworms have several natural enemies. They colonize the crop in the rainy season immediately

after land preparation.

At this stage, populations of the natural enemy are low. Armyworms controlled at the egg and larval stage by parasites. Because of drought, these

parasites fail then armyworms become epidemic. Larvae are parasitized by

Tachinid flies, eulophid wasps (

Euplectrus chapadae

), chalcid

wasps (

Brachymeria lasus

) and braconid wasps (

Cotesia

sp. and

Ropalidia fasciata

). Ants (

Odontoponera transversa

and

Chelonus

formosanus

) are reported as larval and egg parasites.

Moths are parasitized by spiders, Oxyopes javanus and Pardosa pseudoannulat.

Soil-inhabiting insect pests

Soil-inhabiting insect pests do not create the problem in irrigated rice fields because these pests attack and feed on underground plant parts.

Non-puddled, Well-drained, upland rice soils are suitable sites for these pests.Soil-inhabiting pests

described in this chapter are; Ants, Termites,

Crickets, White grubs, Rice root weevil, and Rice root Apids.

Ants

Description:

The ant is a social insect and is distributed widely but commonly found in dry-seeded rice fields in rain-fed wetlands and in upland

rice. The most common species of soil-inhabiting ants that cause significant damage in Asia are

Pheidologeton diversus, Pheidole sp.,

Solenopsis geminata and Munomorium pharaonis.

Damage:

These harvester and fire ants feed on un-germinated rice seeds, and cause rice plant’s destruction. Their nests are

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built on levees or below the soil surface in upland fields. If un-germinated seeds are not available, they attack germinated seeds. Damage by ants

results in a patchy, reduced, plant stand. Ants help aphids in penetrating the soil by making the

tunnels along with the root systems.

Management:

Agronomic Methods:

Ants usually attack at seeds after sowing so in order to reduce loss, an increased rate of seeds is

used.

Chemical Methods:

Seed coating with powdered insecticides helps to control ants in rice fields.

Termites

Description:

Termites belonging to family Termitidae, are subterranean and are commonly known as white ants as they

also possess workers

caste system, king, queen, soldiers, body shape, and wings. They cannot digest cellulose because of the lack of protozoans. Termites culture fungi in

special underground cells that break down cellulose. Termites are a problem in

upland rice areas, but can also occur in light textured soils in rainfed

wetland areas. In Africa,

Macrotermes

and

Microtermes

termites have been recorded as rainfed upland rice pests. Termites are a serious problem

in Africa and Latin America.

Damage:

Soil texture and moisture content are important factors that affect the rate of infiltration. Light textured soils

having low moisture

receive more infiltrations. They preferably attack older plants with greater cellulose content but also

attack a drought-stressed crop. They make

a burrow all the way through plant stems and then eat roots.

Management:

Agronomic Methods: Provide another host at planting time for termites like crop residues that diverts termites from

growing crops. Pulling out of damaged plants from the fields will reduce the dissemination of termites.

Chemical Methods:

Insecticides are used to control termites in rice fields. Granular insecticide applications in seed hills and furrows and seed

treatment with insecticides at planting time are the two most commonly used methods for termite

control.

Crickets

Description:

Four species of mole crickets are reported to attack rice;

Gyllotalpa africana

in Africa,

Gryllotalpa orientalis

Asia, and

Scapteriscus didactylus

and

Neocurtilla hexadactyla

in Latin America. Several field cricket species are identified as

rice pests;

Plebeiogryllus

plebejus

Teleogryllus occipitalis

Gryllus assimilis

Brachytrupes portentosus

Teleogryllus testaceous

Loxoblemmus haani, Velarifictorus

aspersus membranaceus and Gryllus bimaculatus.

Damage:

They live in branched burrows that are 8-10 cm below the soil surface. Under lowland fields, burrow making is common in non-

submerged areas and near the levees while in upland fields, burrows are more in moist patches. These burrows lie near the soil surface and

crickets feed on plant roots. That results in the complete separating of roots from the

aerial parts. Some field cricket species remove the central

portion of leaves and defoliate rice plants.

Management:

Agronomic Methods:

Only agronomic practice for controlling crickets is the maintenance of standing water in the field.

Standing water will prevent crickets to form tunnels in soil and ultimately cannot damage the plant roots.

Chemical Methods:

The main control measure in deep water areas is the chemical treatment of soil as well as seeds at

planting. Another

measure that is recommended is poisoned bait made from powdered or liquid insecticide and from

moistened rice bran can be placed on rice

bunds or in a rice field to kill night-foraging field and mole crickets.

Biological Methods: Sphecid species; Motes manila, Liris aurulenta, Motes loboriosus and Motes subtessellatus, parasitize

the field

crickets. Mole crickets are cannibalistic and regulate their own numbers. Eggs of

Gryllotalpa africana

are preyed by

Pheropsophus jessoensis

larvae

Other parasites are Sphecid wasps (

Larva luzonensis

Larva carbonaria,

and

Larva sanguinea

)

that parasitize nymphs and adults.

Nymph and adults of mole crickets are parasitized by the nematode,

Mermis igrescens,

and the fungus Beauveria bassiana.

Rice Production Knowledge and Practices for Ensuring Food Security

White Grubs

Description:

The term white grubs are actually the large larvae of a scarab beetle. White grub larvae feed on the roots and they are also known as

the chafers. White grubs are a serious damage causing pests of rice and they are distributed widely.

They infiltrate the roots of sugarcane,

cereals, vegetables, millets, and many other crops.

Management

Agronomic Methods:

Delaying land preparation escapes the egg-laying phase of adults or they may die. Weeding also helps

to reduce the

chances of attack by reducing egg laying by females.

Chemical Methods:

The only practical and effective insecticidal control measure is the application of granular insecticides

against white grubs. Insecticides should be applied in crop hills or furrows at sowing.

Biological Methods:

Mermithid nematodes and

Psammomermis

sp. parasitize the grub larvae. Several scoliid wasps, e.g.

Campsomeris marginella modest, parasitize the white grubs.

Rice root aphids

Description:

The rice root aphid,

Tetraneura nigriabdominalis,

is a major upland rice pest. It is reported in Pakistan,

Bangladesh, India,

Sri Lanka, Indonesia, Fiji, Republic of Korea, Japan, Malaysia, Nepal, Tonga, Philippines, Central America,

Africa, New Zealand, the Caribbean, and

Australia.

Damage

: The rice root aphids affect rice crops at different stages. Aphid causes heavy damage at the tillering while light

damage at the seedling

stage. Rice root aphid causes deformed plant growth. Yellowing also occurs. These aphids reside in

plant roots The main damage is caused by the

nymphs and adults feeding, they suck the plant roots sap.

Management

Agronomic Methods:

Increased plant density reduces the chances of Aphid attack so increasing plant density will help

reduce the Aphid

attack.

Chemical Methods:

The usual prophylactic seed or soil treatment with appropriate chemicals or spraying formothion or

oxydemeton methyl

or phosphamidon (@ 250 ml/ha) will prevent the buildup of rice root aphids. Acephate and Carbofuran

are also used as a chemical treatment.

Biological Methods:

Several natural enemies are documented. Lady beetles (

Harmonia octomaculata

Coccinella repanda,

and

Menochilus sexmaculatus

), a mermithid nematode (

Mermis

sp.) and a braconid wasp (

Aphidius

sp.) are recorded parasites

of nymphs and

adults.

Rice root weevils

Description:

Rice root weevil is the most damaging rice pest in Asia. They are widely distributed in Asia specifically in the

Republic of Korea, Japan, and China, and in India.

Damage:

Adults attack transplanted rice but rarely cause economic loss. Larvae cause real damage by attacking the roots

and rootlets of young rice

plants. They attack the redeveloping roots and restrict their development. The leaves give rusty appearance with yellow color and then plants die. The

heavy attack in fields leaves large patches of dry plants. Tillering stage

affected severely compared to other stages.

Management

Agronomic Methods:

Late planting of the crop is recommended. This helps to escape the time of the highest larval attack. In flooded rice,

growing of another crop along with rice can kill larvae. Dense planting decreases populations of rice root

weevil.

Chemical Methods:

Insecticides as a foliar spray and granular insecticides helps to control larvae, but granular insecticides

show promising

effects in controlling adults compared to foliar spray and dipping of rice seeds for 6 h before transplanting is an effective method for controlling larvae

in highly infested areas. Leaf extract of the mahogany tree is used in research,

and it affected the progeny production of rice weevil.

Rice Production Knowledge and Practices for Ensuring Food Security

Rice mealybugs

Description:

Mealybugs are immobile, plant-sucking insects. They are distributed widely all over the world and are

economically important

pests for rice, sorghum, potato, cassava, yam, coffee, citrus, and cacao. To cover themselves, they

secrete white filaments of wax. Mealybugs are

root, stem, or leaf feeders.

B. rehi

occasionally causes rice crop losses in

Thailand, India, and Bangladesh.

Damage:

They suck sap from a stem. This results in yellowing, abnormal tillering, and stunted plant growth. Because the

young nymphs have

restricted movement, damage occurs in patches. Under heavy infestation, panicle does not fully exert

from the boot. Mealybug numbers vary

between hills that cause several spots of depressed growth in the field which are

identified as Sooraj and Chakdhora disease. Drought provides

favorable conditions for the attack, and rice plants can least

tolerate sap loss in this situation.

Management

Agronomic Methods:

Agronomic control measures includes early or late planting to skip the timing of peak infestation.

Flooding of the field

throughout the crop growth period at 5-cm depth helps to reduce the damage because drought condition favors the epidemic. Removal and destruction

of infected plants are done. No resistant varieties to

B. rehi

are commercially

available.

Chemical Methods:

Granular insecticides are operative in standing water. If there is no standing water in damaged fields, broadcasting the

granules is an impractical practice. The waxy discharge covering the mealy bugs protects them from

insecticidal effect. In that case, foliar

sprays are effective.

Biological Methods:

Main natural enemies of the mealybug are lady beetle species (such as

Harmonia octomaculata

Coccinella

repanda

and

Menochilus sexmaculatus

). Dipterous predators of

B. rehi

are two chloropids (

Mepachymerus ensifer

and

Anatrichus

pygrnaeus

) and one drosophilid (

Gitona perspicax

). Hymenopterous parasites of

B. rehi

recorded include; Encyrtidae

(Specie of

Cheiloneurus, Gyranusa, Doliphocerus, Parasyrphophagus, Adelencyrtus, Xanthoencyrtus,

and

Mayeridia

), Eulophidae

(Species of

Tetrastichus, Aprostocetus, Chrysocharis,

and

Desostenus

), Mymaridae (

Lymaemon sp.

), Ceraphronidae

(Cerapkron sp.), Thysanidae

(Thysanus sp.) and Pteromalidae (Diparini sp.and Callitula sp.).

Grain-sucking insects

Description:

Several bugs feed on developing spikelets. They live on grasses or in the rice fields or in the surrounding areas where they reside and

multiply in their vegetative stage. Then they move to flowering rice fields. In Asia,

Leptocorisa sp.

and

in America, Oebalus pugnax are the

important grain-sucking pests.

Rice bugs and Stink bugs

Damage:

Rice bugs adults cause more damage because of a longer feeding period in spite of the fact that nymphs are more

active feeders than adults.

Rice bugs attack at the milk, dough making and even ripening stage of seed. Both nymphs and adult bugs feed on the endosperm of developing grains. In

heavily infested fields, rice panicles contain unfilled grains. Rice bugs attacks on soft endosperm in a solid state and infuse enzymes to predigest it that

results in kernel weakness and discoloration

of mature grain. Damage during the milk and dough stage causes yield loss and poor grain quality,

respectively.

Management

Agronomic Methods:

Several agronomic and mechanical methods are being used to control grain-sucking rice bugs. Late planting is usually

used as an agronomic practice especially for early maturing varieties. This is done in a synchronous

pattern in order to make sure that all crops

mature concurrently. During rice free periods, alternate hosts eradication from

fields, from leaves and from surrounding areas is a good practice

in controlling the bug multiplication.

Mechanical control measures include the use of sticky traps, hand picking of nymphs and adults, and smoking the field.

Chemical Methods:

Granular insecticides are usually futile in controlling grain sucking bugs. Dust formulations or spraying

the insecticides are

sometimes suggested. Use of chemicals (e.g., Acephate) is recommended in some rice growing areas.

Dusting carbaryl @ 10 %, for

Leptocorisa sp.

sufficient and if there is the severity of the infestation, it is repeatedly used.

Biological Methods:

As a biological control, several predators and parasites are recognized to outbreak the rice bug. A typical natural enemy

of stink bug is

Nabis stenoferus

, called the assassin bug. A number of spider’s species, e.g.,

Tetragnatha

Rice Production Knowledge and Practices for Ensuring Food Security

javana

Neoscona thesis

and

Argiope catenulate,

target on nymphs and adults of rice bug. Eggs of

Leptocorisa sp.

are destroyed by small scelionid

wasps (

Gryon Nixon

). Stink bugs are parasitized by several wasps species. The meadow grasshopper,

Conocephalus longipennis,

preys on rice

bug eggs. A fungus,

Beauveria bassiana

, preys on both nymphs and adults.

Rice leafhoppers and planthoppers

Description:

Leaf and planthoppers not only cause feeding damage, but they also cause viral diseases by acting as vectors. The more damaging

species in Asia are the zigzag leafhopper

Recilia dorsalis

, green leafhoppers

Nephotettix sp.,

the white- backed planthopper

Sogatella furcifera

the small brown planthopper

Laodelphax striatellus

, and the brown planthopper

Nilaparvata lugens

and

Tagosodes orizicolus

. The rice

delphacid

Tagosodes orizicolus

is found in the north-central region of

South America and the southern USA. Three

Nephotettix

species;

Nephotettix nigropictus

and

Nephotettix virescens

are found

in tropical and temperate Asia.

Damage:

Leaf and planthoppers damage plants by plugging phloem and xylem through sucking the sap. Similar effects appeared due to

excessive oviposition. The ovipositional and feeding marks incline plants to be a bacterial and fungal infection. Honeydew boosts sooty molds

due to a toxin injected during feeding on plants infested with

Cicadulina bipunctella.

Leaf and planthoppers are also vectors of rice viral diseases.

Nephotettix virescens

is a vector of tungro viruses,

Nilaparvata lugens

spreads grassy and ragged stunt virus in South Asia and Southeast Asia,

Laodelphax striatellus

act as a vector of a most dangerous disease, rice stripe in East Asian countries and

Tagosodes orizicolus

causes the spreading

of ‘Hoja Blanca’ virus.

Management

Agronomic Methods:

Nitrogen application in three split doses is effective in minimizing the population rate of

Sogatella furcifera and

Nilaparvata lugens.

Silicon application is positively connected to reduce the planthopper population in rice fields. Water favors the growth

of planthoppers and leafhoppers so 3 or 4 d fields draining during invasion have been

endorsed for reducing

Sogatella furcifera

and

Nilaparvata lugens

populations. For

Nilaparvata lugens,

closer plant spacing

is considered as an important factor favoring hopper build-up.

Lower plant portion is slightly cooler due to low sunshine,

humidity and provides a favorable microclimate for pest population build-up.

Field sanitation for control of leaf and planthoppers is used in many rice growing areas. Volunteer rice and ratoons

may act as a source for

the spread of a virus.

Rice crop rotation is an economical control measure. For this purpose, legumes are usually grown in most areas of

Asia for reducing leaf

and planthopper infestations.

Use of trap crop to control

Nephotettix virescens

and

Nilaparvata

lugens is suggested in a study conducted at IRRI. Trap crop

transplanted 20 d before crop transplanting and it reduced the attack of

Nilaparvata lugens

on the main crop. Similarly, The banker plant

system is also used in some countries, and it can boost the population of

A. nilaparvatae that

helps to control rice planthoppers. In the Jiaxing

City of China, the incidence of planthopper transmitted viral diseases is

considerably decreased by delayed sowing and non-significant

variation in the grain yield is observed.

The frequency-vibration-based pest lamps used to kill the planthoppers. They are installed at 200 m distance from each other in a

checkerboard pattern and 1.3–1.5 m above the ground. These lamps are switched on during the light period

when immigration of planthoppers

occurs. However, a disadvantage of these lamps is that it will also cause damage to

beneficial insect pests.

Host-plant resistance is helpful in decreasing the damages. In a study in China, about 29 dominant resistance genes

for planthoppers have

been recognized from wild rice species and indica rice varieties. The transgenic rice plants with snowdrop Lectin (

Galanthus nivalisagglutinin

)

have reduced the fecundity and survival rate by postponing the development

of planthoppers because of there by an antifeedant activity.

Chemical Methods:

For the control of leaf and planthopper vectors, insecticides application is used that not only reduces the effect of leaf and

planthopper but also reduces the spread of the virus. The strategies used in chemical control of leaf

and planthopper vector successfully are linked

to vector behavior and virus transmission characteristics. With

Nephotettix

virescens,

direct feeding is more damaging than the tungro virus

transmitted by the vector. Tungro is a non-persistent virus and spread during a short feeding period, whereas grassy stunt and ragged stunt viruses

are persistent and require more

Rice Production Knowledge and Practices for Ensuring Food Security

time. Therefore, rapid knockdown and prevention of feeding of the leafhopper are important. In tungro epidemic areas,

prophylactic procedures are used for protection against this virus.

For

Nilaparvata lugens,

insecticide application at young nymph stage is inefficient because young nymphs do not

cause damage to the crop. The insecticide should be applied only at an economic threshold level of population.

Leafhoppers are more responsive to insecticides than planthoppers. Most commonly recommended insecticides are chlorinated

hydrocarbons, organophosphates, and carbamates in the Republic of Korea and Japan, but organophosphates

have the highest selectivity against

Laodelphax striatellus, Nilaparvata lugens,

and

Sogatella furcifera.

Organophosphates have a lower level of ovicidal activity than

carbamates.

Buprofezin is extremely discerning molting-inhibitor for

Nephotettix cincticeps, Nilaparvata lugens, Nephotettix

virescens,

Laodelphax striatellus, and Sogatella furcifera, Buprofezin is found nontoxic to fish, or mammals.

For tungro virus control, systemic granules of insecticides are suggested for soil incorporation before seedbed

sowing. Soil

incorporated granules are advantageous than sprays or broadcast granules in the seedbed.

Broadcasting or soil incorporation of systemic granules provides protection to crop for 40 d whereas, seed soaking

in insecticide

solution before transplanting for 6-12 h gives protection for 20 d.

Insecticide sprays are more effective than a granular application for control of

Nilaparvata lugens.

However, in many

countries, leafhoppers and planthoppers developed resistance against organophosphates carbamates and carbofuran.

Biological Methods:

Several pathogens, parasites, and predators attack at all stages of leaf and planthopper. Inappropriate insecticides

application may destroy the population of natural enemies that results in a striking outbreak of pest. Most

effective parasites of

Nilaparvata

lugens

eggs are; trichogrammatid (

Paracentrobia andoi

), mymarid (

Anagrus optabilis

), and eulophid wasps (

Tetrastichus formosanus

Parasites of

Nilaparvata lugens

nymphs and adults are; dryinid wasp (

Echthrodelphax bicolour

), elenchid strepsipteran (

Elenchus

yasumatsui

), fungal pathogens (

Hirsutella citriformis

and

Beauveria bassiana

), and nematode parasite (

Hexamermis sp.

). Underwater

aquatic predators (e.g.,

Cybister sp

.) and surface

predators (e.g.

Ranatra dimidiate

atrolineata

Mesovelia vittigera

and

Microvelia douglasi)

prey on hoppers in water bodies.

The beetle,

Ophionea,

actively explore foliage for

Nilaparvata lugens

nymphs and adults. Damselfly and dragonfly prey on adults and

nymphs. In laboratory tests, a single

Pardosa pseudoannulata

used up about 45 planthoppers/d. A white

fungus,

Beauveria bassiana

, grows

and covers the body of dead leafhoppers and grows inside it.

Common predators of eggs are

Cyrtorhinus lividipennis.

Parasites of nymphs and adults are dryinid wasp (

Echthrodelphax

fairchildii

), pipunculid flies (

Tomosvaryella oryzaetora, Pipunculus mutillatus

), and strepsipteran. Greater

than 50% parasitization of green

leafhoppers by pipunculids is reported. Biological insecticide, 9% 12 α-hydroxy rotenone

EW, shows greater insecticidal effects on

planthoppers.

Rice gall midge

Description:

The rice gall midge

Orseolia oryzae

(Wood-Mason) is one of the most damaging pests of rice in South and

Southeast Asia. It also

occurred in several parts of Pakistan, India, Sri Lanka, Cambodia, Laos, Nepal, Myanmar, Indonesia, Vietnam, and northern Thailand. It also occurs in

Ghana, Ivory Coast, Cameroon, Liberia, Mali, Nigeria, Niger, Sudan, and

Senegal.

Damage:

The gall formed by the activity this fly is popularly known as ‘anaikomban’ ‘onion shoot’ or ‘silver shoot’. Hollow pink or purple, pale

green or dirty white tubes at the tip of the leaf, a reduced green leaf blade with auricles and ligules are formed. It also invades the rice nursery but

tillers are ideal for their attack. It may cause up to 50% rice yield loss in a heavily

infested crop.

Management

Agronomic Methods:

The use of suitable amounts of nitrogen fertilizer in split doses on different growth stages is suggested. Field sanitation helps

a lot to control the spread of gall midge. Removal of alternate hosts from fields is recommended controlling the pest population. Keeping land

fallow free of off-season host plant and field plowing after harvest is

recommended. Planting should not be done in neighboring fields within 3 wk

to avoid staggered ages crops. Delaying planting of photoperiod-sensitive varieties helps decrease rice gall midge infestation because the vegetative

stage is more prone to

Rice Production Knowledge and Practices for Ensuring Food Security

gall midge attack.

Chemical Methods:

Insecticides are not recommended for gall midge control because larvae reside and protect inside

the gall and plant.

However, granular insecticides are applied sometimes. Granular insecticide applications at any rate in standing water in the field are usually

effective than foliar sprays. Seed treatment with chlorpyriphos (0.2%) emulsion for

3 h is suggested in some rice-growing areas of the world. Seed

mixing with either imidacloprid (0.5 kg /100 kg seeds) or chlorpyriphos (0.75 kg/100 kg seeds) provides protection for 30 d in the nursery.

Seedling root dipping for 12 -14 h in 0.02%

chlorpyriphos emulsion before transplanting provides 30 d protection.

Biological Methods:

Numerous predators and parasites attack at gall midges. The natural enemies, controlling the African and Asian rice gall

midge are diverse. Several platygasterid wasps are parasitoids of larvae and they start laying eggs on silver shoot walls when they first sting the

larva from inside. The new hatchlings attack on the gall midges. A phytoseiid

mite, Amblyseius imbricatus, and Bracon sp., aff. annulicornis,

Platygaster pachydiplosisae, Anisopteromalus camerunus,

and Neanastatus tenuis platygasteri,

attacks on eggs of Asian and African rice

gall midges

Several pupal parasitoids e.g.,

Neanastatus cinctiventris

and

Neanastatus

oryzae, and solitary larval parasitoids, e.g.,

Obtusiclava oryzae

are also known. Adult midge is preyed by many spiders species, e.g.,

Neoscona theisi

Argiope catenulata

and

Tetragnatha mandibulata

Rice leaf folder

Description

: Larvae of eight pyralid moths’ species roll or fold the leaves of graminaceous plants. They are

Marasmia exigua

Cnaphalocrocis

medinalis

Marasmia bilinealis

Hampson,

Marasmia patnalis

Marasmia suspicalis

Marasmia ruralis

Marasmia

venilialis,

and

Marasmia

trapezalis

. They are found in the rice-growing tracts of 29 temperate and humid tropical countries

of Asia, Australia, and Africa.

Damage:

Several epidemics of leaf folders have been reported in the Republic of Korea, Fiji, Bangladesh, Philippines, China,

India, Sri Lanka, Japan,

Nepal, Vietnam, and Malaysia.

Under favorable conditions, several generations of leaf folders are produced. Only 1 larva/leaf is found. After feeding

for about 2-3 d, larvae

move to another leaf. Thus, each larva destroys more than one leaves during its growth period. The high insect population causes rice plants to dry

up and appear scorched. The larvae longitudinally fold the leaves before

feeding and fasten the leaf margins with threadlike silk stitches. Feeding

affects the photosynthetic ability and vigor of the infected rice plant. The damaged leaves are the entry points for bacterial and fungal infections.

Feeding on flag leaf by leaf

folders caused maximum yield loss.

Management

Agronomic Methods:

Nitrogen fertilizer management is highly recommended. N fertilizer plays an important role in

improving the yield,

in increasing the nutrition of the rice plant but it also helps to greater insect feeding rates, survival, and

reproduction which in turn leads to greater

damage. Nitrogenous fertilizer application in split doses is helping to reduce

the growth, reproduction and surviving ability. Other fertilizers such

as phosphorus, potassium and necessary elements

should be applied in balanced amounts. They can enhance the rice plant vigor and improve the

resistance of rice plants to

leaf folders.

Removal of the alternate host plant is recommended e.g. grassy weeds removal from rice fields and surrounding

borders that prevent

the rice leaf folders build-up on alternate hosts. Varietal resistance can be used to reduce the damage caused by leaf folders. Bt rice posses first-rate

insecticidal activities against leaf folders. Sex pheromone application can

decrease the insecticide use by 1–2 sprays and the input costs can be

decreased than insecticides.

Chemical Methods:

In order to control severe leaf folder influx, chemical control is done. A most effective method of applying an insecticide is foliar

sprays. Foliar sprays are needed to be repetitive because of washing off insecticides by frequent

rains. Granular insecticides application by the

broadcast method is ineffective. However, insecticide created resurgence of

ilaparvata lugens

acts as hindrances to successful chemical control.

Fields should be monitored weekly because leaf folders

can attack the crop at any growth stage.

Biological Methods:

Several natural enemies of rice leaf folders normally push them underneath economic threshold levels.

Several species of

nematode (

Agamermis sp.

), Diptera (e.g.,

Argyrophylax sp.

and

Megaselia sp.

), Coleoptera (

Coccinella sp.

and

Chlaenius sp.

), Orthoptera

(Metioche sp.

and

Anaxipha sp.

), Hymenoptera

(Apanteles sp., Trichogramma sp., Goniozus sp.,

Rice Production Knowledge and Practices for Ensuring Food Security

and

Bracon sp.

) and Araneae

(Tetragnatha sp., Argiope sp.

and

Pardosa sp.

) have been reported as parasites and predators

of leaf folders in

Asia. Spinetoram, Spinosad,

Empedobacter brevis

and

Beauveria bassiana

possess grater insecticidal effects on stem borers. A few viral, fungal

and bacterial pathogens and toads and frogs also parasitize the larvae, when the pest

population is high. The biological insecticide 9% 12 α-hydroxy

rotenone EW show greater insecticidal effects on leaf folders.

Microbial insecticides, e.g.

Bacillus thuringiensis

, are effective against larvae.

Rice water weevil

Description:

The rice water weevil (

Lissorhoptrus oryzophilus

) was originally found in the Mississippi River basin., but it is

now one of the

most destructive rice pests in all rice growing areas.

Damage:

Adults feed on young rice plants and cause damage to leaves. Longitudinal strips are formed on the leaf surface.

Maggots cause the main

injury. They feed on the roots, severely pruning them in heavy infestations and causing vigor loss,

reduced yields and plant lodging.

Management

Agronomic Methods:

Early planting of rice can skip the time of pest attack and reduce the yield loss. In Japan, early

transplanting of rice

seedlings early reduces yield loss. Losses can also be decreased by transplanting middle-aged or mature seedlings. Intermittent rice fields flooding and

draining at 15 d intervals reduces the damage. However, this practice has a limitation in areas where water availability is low and the loss of fertilizers

also occur due to drainage. Removal of alternate

hosts plants e.g. aquatic grasses, reduce the pest population. Areas receiving higher doses of

fertilizers are more sternly

infested. Rice resistance varieties to rice root weevil are recommended. Several rice varieties with low or moderate levels

resistance are recognized.

Chemical Methods:

Granular insecticides are suggested and applied at the appropriate time.

Biological Methods:

The fungus,

Beauveria bassiana,

attack on rice water weevil. A mermithid parasitized the female

weevils in the USA.

Several frogs and bird species are recognized to feed on the rice weevils. Tettigoniid grasshoppers such

as Orchelimum agile, Conocephalus

fasciatus and eoconocephalus triops prey on adult weevils.

Rice thrips

Description:

The two most common species associated with rice are

Haplothrips aculeatus

and

Stenchaetothrips biformis

S. biformis

is a major rice pest in India, Sri Lanka, Japan, Bangladesh, Indonesia, and China.

S. biformis

is also known as rice

paddy thrips, oriental rice thrips, and rice leaf thrips. The first specimen collected from watercourses.

Damage:

Larvae, as well as adults, possess scratchy mouthparts. Thrips species with leaf-feeding habit possess a punch and suck feeding technique.

Symptoms of damage include; leaves rolling inward along the margins, stunting and wilting. Fine, silvery or yellowish streaks appear. In a severe

epidemic, plant death occurs, resulting in a low plants number/unit area. The

damage is severe in dry land rice fields.

Management

Agronomic Methods:

For rice thrips control, flooding the field for 2 d to submerge plants is an effective practice. Use of resistant varieties can

reduce the chances of thrips attack. Many rice varieties resistance to thrips have been identified.

Wild rice with resistance to thrips includes;

Oryza glaberrima. Oryza eichingeri, Oryza minute, Oryza officinalis, Oryza nivara,

Oryza perennis, Oryza sativa f. spontanea and Oryza

rufipogon.

Chemical Methods:

Insecticides as sprays, as systemic granules or dust controls pest build-up. In china seed treatment

with methoxam

reduces the trips infestation more effectively compared to the foliar application. Imidacloprid, carbosulfan,

thiamethoxam, and thiacloprid are the

insecticides most commonly used as seed treatments against rice thrips.

Rice caseworm

Description:

The rice caseworm,

Nymphula depunctalis,

is an important insect pest of rice. It occurs in Africa, in Australia, South America, and

many tropical countries. Among related species are;

Paraponyx fluctuosalis

, which occurs in Australia, Japan, India, Philippines, Sri Lanka, China,

Malaysia, Thailand and in some African countries,

Nymphula fengwhanalis

and

Nymphula vittalis

, which occur in China and

P. diminutalis

which occurs in India, Japan, China, Indonesia, Philippines,

Thailand and Sri Lanka.

Rice Production Knowledge and Practices for Ensuring Food Security

Damage:

The freshly hatched larvae attack and feed on the tender leaf surfaces, but larvae at later stages, feed on the surfaces

of the older leaves. Larvae

caused the damage by feeding and cutting off the leaf tips forming a case. Removed leaf tissue

gave the ladder-like appearance, while upper

epidermis gave the papery appearance. They gave smaller panicles and less

number of tillers and delayed maturity. If other pests such as stem borer

or whorl maggot infest the crop within first 30 d of

transplanting, yield loss occurs and plants’ ability to recover is decreased.

Management

Agronomic Methods:

Agronomic methods involving older seedlings transplant helps in limiting the period of larvae attack. Water management

is also effective in controlling larvae of rice caseworm. Field draining for about 3 ds will exterminate

most of the larvae because of low supply of

oxygen. A non-flooded seedbed is protected from caseworm attack. However, this

practice favors weed growth.

Chemical Methods:

Larvae of rice caseworm are sensitive to insecticides. So, the foliar spray is recommended. They have controlled readily

with granules application in floodwater or with foliar sprays. Within one week of transplanting, the

insecticidal foliar spray is

recommended.

Biological Methods:

A tabanid fly;

Tabanus sp.

and a braconid wasp;

Dacnusa sp.

parasitize the caseworm larvae. The hydrophilids

(e.g.

Berosus sp.

Cybister tripunctatus orientalis Gschwendther

and

dystiscids Laccophilus difficilis

are reported

predators of caseworm

larvae. Algae and snails foraging such as

Radix

sp. and

Pila sp.

may remove caseworm eggs from rice leaves. Red ants attack the larvae in infested dry

field rice. Several spiders of Araneidae;

Araneus inustus,

and

Neoscona theisi,

one species of Clubionidae;

Clubiona japonicola

; one species of

Tetragnathidae;

Tetragnatha nitens

; one species of Lycosidae;

Pardosa pseudoannulata prey on the moth.

Whorl maggots

Description:

Whorl maggots consist of a composite of several species of genus

Hydrellia.

All members of the genus are a leaf or stem miners. They

prefer living in damp areas or near water. In the field, rice whorl maggots resemble with other flies.

Because of this resemblance, rice whorl

maggots are difficult to identify.

Rice whorl maggot/South American Rice Miner

Description:

The rice whorl maggot,

Hydrellia philippina,

was first documented in the Philippines in 1962, as a serious pest

of rice. The insect

attacks only rice plants usually at the vegetative stage, in the irrigated fields. It feeds on the central whorl

of the leaf. It is a semi-aquatic pest.

Damage:

The fly maggots attack unfurled leaves. The hatchlings move to the center and feed on the mesophyll tissue.

Chewed-up and discolored areas appear. These areas ultimately dry up and leave often droop.

Management

Agronomic Methods:

Crop establishment methods result in insignificant damage because plants cover the water surface.

Water surface

covering with Azolla helps to restrict invasion. Recommended agronomic control is rice fields draining because adults are attracted to standing water. It

is good to use mature seedlings to curtail the crop vegetative stage. Draining should

be done during the first 30 DT at intervals of 3-4 d. Drained fields

allow more growth of weeds. Direct-seeded seedbeds or

fields are not striking to adults so direct seeding is recommended. Use of resistant varieties

is recommended however only

a few resistant varieties are available against whorl maggots.

Chemical Methods:

Soil application of systemic granules before transplanting or broadcasting of non-systemic granules in

standing water are

usually more effective methods for whorl maggots’ control. However, foliar sprays can be done 1 or 2 wks

after transplanting.

Biological Methods:

Wasps

Trichogramma sp.

parasitized the exposed eggs of whorl maggots on leaves and braconids

parasitized the

whorl maggot larvae. Another parasite of whorl maggots includes; araneid (

Neoscona theisi

), lycosid (

Pardosa

pseudoannulata, Oxyopes

javanus

) and a fungus of the genus

Entomophthora.

Adult whorl maggots are preyed upon by

ephydrid flies (Ochthera brevitibialis).

Ladybird beetle

Description:

The ladybird beetles are oval, convex, small, insects. A large number of these species act as predators. They

Rice Production Knowledge and Practices for Ensuring Food Security

grow on planthoppers, leafhoppers, aphids, and mealy bugs and on the eggs of many other insects. The most common and

widely distributed are Micraspis crocea and Micraspis discolor.

Damage:

Ladybird beetle has variable feeding habits. Adults and nymphs of ladybird beetles usually feed on planthopper, aphid and leafhopper

nymphs, and adults, eggs of mealy bugs, thrips, and stem borer. In the absence of prey, they attack

pollen and leaf blades (leaving small chewed

areas) and recurrently damage grains.

Management

Organophosphate insecticides spray helps to control rice beetles. These beetles are predators of several harmful

insects. Controlling

or reducing prey population helps to control beetles.

Rice black bugs

Description:

The two most important and common species of black bugs are the Japanese rice black bug,

Scotinophara

lurida

and Malasyan

rice black bug,

Scotinophara coarctata

that attack rice plants. They are also known as rice pentatomid bugs.

Scotinophara lurida

occurs in Japan,

Taiwan, China, Sri Lanka, and India while

Scotinophara coarctata

occurs in Taiwan,

China, Indonesia, India, Malaysia, Thailand, Vietnam,

Philippines, and Cambodia.

Damage:

Both nymph and adults of rice black bug cause damage to plant by feeding the sap. They usually reside at the plant

base. At the start of the

day, they feed on upper parts of plants. But when sunlight intensity is high, they invade to undersides

of stem and leaves and continue feeding there. At

night, they become active and incessantly feed throughout the night.

Management

Agronomic Methods:

Destroying the host plants usually b plowing the field is an important agronomic practice to control

black bugs. Black bugs

persist in the rice stubbles even after harvest, plowing is done to control the pests. Sunlight plays an

important role in destroying black bugs. Weed

removal allows more sunlight to arrive at the rice plants bases and kills the

bugs.

Chemical Methods:

Spraying the insecticides at the plant base is a most effective way to control black bugs. This practice is

done because black bugs stay at the base of plants.

Biological Methods:

Several natural enemies of the rice black bug are reported. These include; gryllid (

Metioche vittaticollis

coccinellid (

Micraspis crocea

), carabid (

Agonum daimio),

nabid bug (

Stenonabis tagalicus

) and spiders (

Pardosa pseudoannulata

Oxyopes

javanus

Tetragnatha virescens

, and

amaricus formosus).

Some fungi also act as a predator of black

bugs e.g. Paecilomyces lilacinus,

Beauveria bassiana, and Metarhizium anisopliae.

Colaspis

Description: Two species of colaspis; Colaspis louisianae, and Colaspis brunnea, are found throughout rice-growing areas.

This pest usually causes damage to dry- seeded rice fields in a soybean-rice rotation.

Damage:

Colaspis larvae start feeding on the plant roots when rice or any other crop is sown into a field. Fine root hair feeding by larvae may

result in the death of the plant. The larvae will then pupate and develop into adults. Adults will not lay eggs on rice crop but will migrate to a nearby

soybean field. Clumped larval distribution in the soil and patches of reduced

plant stand loss are commonly found.

Management

Application of permanent flooding is the only agronomic practice that helps to minimize the pest attack. These pests do not

live in water and they

cannot survive continuous flooding. This is why they are not a serious problem in water-seeded rice.

Panicle Rice Mite

Description:

The panicle rice mite (PRM),

Steneotarsonemus spinki

, is a pest of commercially produced rice in Asia, the

Caribbean and

Central America. This pest causes significant damage to rice crop, especially in the presence of bacterial

panicle blight and sheath rot.

Damage:

The panicle rice mite attack and damages the plants both directly by feeding on rice leaves, kernels, and stems

and indirectly by acting

as a vector of viral, fungal, and bacterial pathogens. Feeding destruction can cause the sterile grain

Rice Production Knowledge and Practices for Ensuring Food Security

syndrome, which is designated as a brownish, loose flag leaf sheath, damaged grain development with un-filled grains and

brown spots, a twisted panicle neck, and erect panicles standing.

Management

All the control methods used for sheath rot and bacterial panicle blight will help to reduce the effect of this pest.

Chinch Bug

Description:

Chinch bugs (

Blissus leucopterus leucopterus

) hibernate as adults in leaf litter, grass clumps, and other protected areas. They emerge

in early to mid-spring for feeding and mating on grass hosts and on rye, wheat, barley, and oats grains.

Damage:

Chinch bugs are sporadic and create more damage in drill-seeded rice because of the delayed application of permanent flood.

Economic damage to rice usually occurs when different production practices and favorable weather

conditions sanction chinch bugs to reside

on wheat, corn and sorghum fields. When these crops are harvested at maturity,

chinch bugs may migrate to young rice plants in nearby fields.

Crop stand is reduced.

Management

Agronomic and chemical control methods are available. Agronomic control consists of flooding the fields, force the chinch bugs to migrate

to rice foliage where they can be controlled with an insecticide. This practice necessitates that rice

plants be large and levees be in place to resist a

flood. Agronomic control is usually more costly than chemical control.

Rice Leaf Miner

Description:

The rice leaf miner (

Hydrellia griseola

) is a sporadic problem in rice growing areas. Leaf miner attacks on the crop in the early spring

and epidemic occur usually in the deep water, on the upper side of levees. Rice leaf miner is usually

not a problem in 4 to 6 inches deep water.

Damage:

The attack is more severe in continuously flooded rice fields with more than 6 inches deep water. Larvae make a

tunnel between leaf

layers. Leaf miner usually attacks and kills the leaves that are close to the water. Under heavy infestations,

the entire plant may die and severely

reduce the plant stand.

Management

Rice leafminer management involves agronomic control or insecticide application, perhaps both. Important agronomic

practice is maintaining the water depth at 4-6 inches. Lowering of water level in rice fields helps to prevent injury.

Rice Seed Midge

Description:

Adult rice seed midges (

Chironomus sp.

) always occur in flocks on levees, rice fields, and roadside ditches and

in other water bodies.

Damage:

Midge usually attacks water-seeded rice. Larvae injure rice by feeding on the seeds of very young seedlings, on germinating seed

embryo and on the developing roots. In flooded fields, the potential of infestation increases. Midge

infestation can be from insignificant (not

economically important) to very severe.

Management

Most important agronomic method to control rice seed midge is field draining as this pest grows better in flooded

fields. Draining the field

will reduce the midge number. Sometimes, reseeding in highly infested fields is required. Methods that encourage rapid seedling growth and seed

germination, such as avoiding cool weather planting and using pre-sprouted

seed will help to escape vulnerable midge attack stage and reduce

serious damage.

Rice diseases and their management

Seedling Blight

Description:

Seedling blight, or damping off, is caused by several soil-borne and seed-borne fungi, including species of

Curvularia

Cochiobolus

Fusarium, Sarocladium

Sclerotium,

and

Rhizoctonia

. Brown thin and irregular spot on growing point

or coleoptiles of rice appear.

Fungi penetrate the undeveloped seedlings and injure them. Blighted seedlings that come out

of the soil, dies out suddenly after surfacing.

Rice Production Knowledge and Practices for Ensuring Food Security

Management

Suitable agronomic practices, such as sowing of early maturing varieties will decrease the effect of fungi. Draining the field and seed

planting under optimum temperature, are the best control measures for this disease. Treating seed with seed-protectant fungicides (e.g. mefenoxam,

metalaxyl, thiram, and mancozeb) effectively decreases the seedling blight and

gives satisfactory stand.

Water Mold

Description:

It is a fungal (

Achlya

sp. and

Pythium sp.

) disease. Water mold is noticed as a fungal ball strand around seeds on

the surface of the soil.

Seeds are rotted after draining seeding flood. This result in a greenish-brown or copper-brown spots on soil surfaces or above, about a dime size with

central rotted seed. The color is due to green algae and bacteria, mixed with

fungal hyphae.

Management

Draining and flushing the seeding helps prevent water mold. Pin-point flooding helps in reducing damage caused by water-mold. Sowing

should not start till the mean daily temperature reaches 65

C. Seed treatment with suggested fungicides

helps to reduce the damage.

Crown Rot

Description:

It is a minor disease of rice caused by

Erwinia sp

. This disease is observed rarely. During tillering, symptom first

appears. The crown

area is rotten and becomes soft that extends into lower internodes with a fetid odor. Tiller starts dying, one at a time. Roots die and turned black, with

discolored streaks. A similar crown discoloration is caused by misapplication

of a hormonal herbicide (e.g. 2, 4 –D.).

Management

No specific control practices are generally recommended.

Root rot

Description:

Root rot is a fungal disease also called as feeder root necrosis, caused by

Phytium dissotocum

Pythium spinosum,

and other

Pythium

sp.

This disease causes black discoloration of roots. As the root deterioration occurs, absorption of nutrient

is reduced. The leaves become yellow

and plants lack vigor.

Management

Proper fertilization reduces the disease symptoms however nutrient use is reduced. Control of rice root weevil can help to reduce root rots.

Field draining enhances root growth but can create problems with nutrient use efficiency, blast, and

weeds.

Root knot

Description:

Root-knot is caused by nematode

Meloidogyne

sp., found only under dry-land conditions. Symptoms include

swollen areas of

the roots and formation of knots or galls. Plants are a yellow color, dwarf, and lack vigor.

Management

The disease is rare and yield losses are low. Prolonged flooding of field is recommended as nematode becomes

inactive.

Rice blast

Description:

A most important disease of rice worldwide and occupies the first position in terms of causing damage in intense rice cultivation

areas. The causative agent of this disease is

Pyricularia oryzae

. This disease is also named as rotten- neck blast, node blast, leaf blast, collar blast and

panicle blast depending on the portion of the plant affected. The disease

disseminates through seeds, wild grasses and diseased plant debris lying in

the field. Small spots appear on grains, leaves, nodes, and panicles and sometimes on leaf sheaths. The spots start as small, greyish, bluish or whitish,

water-soaked dots.

These spots rapidly multiply and their center turns grey. Black and brown spots also grow on glumes and inflorescence. In later

stages, diseased heads blasted, and color becomes white. Grain development is affected and the panicles droop.

Rice Production Knowledge and Practices for Ensuring Food Security

Management

If the disease is not widespread in an area, the blast can be controlled by burning and destroying the diseased plant debris and stubble,

avoid over nitrogen fertilization as this increases the plant's receptiveness to the disease. Early planting, use of healthy seed, dusting the seed with

the seed dressing organic mercurial fungicides, spray the crop with

organo-mercurial, cultivation of resistant varieties, avoid excessive

application of irrigation water and utilize good water management to ensure that plants do not experience water stress. Also avoid and control the

excessive population of plants, grasses, and weeds. The disease might be successfully controlled by systemic fungicides when they are available. In a

study in Nepal, Tricyclazole 22% + Hexaconazole 3% fungicide proved effective in controlling rice blast when applied at weekly

intervals starting

from the booting stage. Silicon application to rice crops showed a positive effect in combating rice blast

disease.

Brown spot

Description:

Brown spot is caused by the fungus,

Cochiobolus miyabeanus

and it is one of the most prevailing rice diseases

around the world.

It is also known as Helmintho-sporium leaf spot. This is another leaf spot disease that frequently occurs.

The main cause of this disease is poor soil

conditions. Round, brown lesions having a yellow halo appeared on leaves. Size of

lesions fluctuates from the size of a pin-head to rice grain. As lesion

grows, they remained round with necrotic grey center

and reddish-brown to dark brown margin. These brown spots cause severe damage

and ultimately leaf dies.

Management

Sowing of good quality seed and good land preparation helps to reduce the disease incidence. Destruction of stubble, sanitation and crop

rotation are mostly used agronomic practices. Chemical seed treatments like appropriate fungicides are effective in reducing the prevalence of the

disease. Copper fungicides spray in the right amount and at right time will reduce the damage. Disease resistant varieties are also grown to reduce

chances of disease occurrence. Plants must be provided

with correct nutrients, at the proper time and in the proper dose. Avoiding water stress in

field reduces the propagation of

disease.

Narrow brown leaf spot

Description:

The causative agent of this disease is called

Cercospora janseana

. This disease differs in rigorousness from

year to year and

becomes more rigorous as rice plants mature. The disease occurs in major rice-growing regions in Africa, North, Central and South America, tropical

Asia and Australia. Long narrow reddish-brown or brown lesions appear that are

parallel with leaf veins. These lesions usually constrained between

veins. The lesion may expand across veins that can kill

leaves. The lesion can also appear on the leaf sheath.

Management

Treating seeds with appropriate fungicides or sometimes with hot water, before planting, can diminish the prevalence

of the disease. However,

chemical application is not currently suggested for this disease. Use of resistant varieties is also

recommended.

Leaf smut

Description:

Leaf smut is a distributed widely and is caused by a fungus,

Entyloma oryzae

. Lesions appeared on leaf blade that is small, black,

and linear and may have a light brown or dark gold halo. Leaf tip dries up and becomes gray as plants

reach maturity. Lesions are usually

present on the upper sheath.

Management

Foliar fungicides (e.g. trifloxystrobin and propiconazole) are usually applied. Leaf smut attacks in the late rice

growing season and causes minor losses.

Leaf Scald

Description:

This disease is caused by a pathogen,

Gerlachia oryzae

and it is severe in West Africa and Latin America.

Damage may vary

depending on growth stage, plant density, and cultivar. Leaves gave the scalded appearance. The lesion

is consisting of a different zone of alternating wide bands of grey color with light tan and dark brown narrow bands from

Rice Production Knowledge and Practices for Ensuring Food Security

leaf tips or edges. Lesions often are tan marks with golden or yellow borders at leaf edges. Light brown halos appear as the

lesions mature. Leaf tips

and margins are translucent.

Management

Application of only recommended amount of nitrogen fertilizer in split dose helps to reduce the disease susceptibility. Growing of resistant

rice varieties is an important preventive measure. Foliar fungicides (trifloxystrobin and propiconazole) application is recommended. But these

fungicides are not applied after the rice seedhead emergence. Treat the seeds with

suitable fungicide (e.g. iprodine and propiconazole).

Bacterial leaf blight

Description:

Bacterial leaf blight is caused by a bacterium called

Xanthomonas campestris

. This is a serious rice disease during

the rainy season.

Elongated lesions appear near the tips of leaves or edges that are several inches long and water soaked in appearance. Leaf tips or edges turn firstly into

white, then yellow and finally gave grey color due to fungi (Saprophytic fungi).

Leaf edges become wavy. Death of leaf and plant occur, and

grains remain empty.

Management

Bacterial blight can be managed effectively by plowing the straw and stubble into the soil after crop harvest. The

burning of diseased

stubble helps to reduce the chances of disease transfer. Appropriate land preparation and sowing good quality seed reduce the chances of disease

manifestation. Resistance varieties are also used to avoid this disease. Excessive nitrogen application in the field increases the chances of disease

manifestation. To avoid this situation, nitrogen application

is done in split doses.

Stack burn

Description:

It is also called Alternaria leaf spot, caused by a fungus,

Alternaria padwickii

. It is common in rice growing areas of the world. White or

pale tan, round or oval spot appear with marrow reddish-brown margin. Two adjacent spots merge

and form a double oval spot. In the center

of the spot, a small black fruiting structure appears.

Management

Seed treatment with fungicides will decrease the seedling blight and in turn, will reduce the chances of leaf infections

by reducing the

number of available spores.

White leaf streak

Description:

White leaf streak is caused by a fungal pathogen,

Mycovellosiella oryzae

. It is very similar to narrow brown

leaf spot except that

the spots are a little broad and have white centers. White leaf streak is widespread in West Africa and tropical Asia. Lesions are long, narrow with

brown border and white center appears on leaves. Pathogen lives on infected straw and seed. The pathogen may go through the plant from cuts and

bacterial exudates can blow out in irrigation water.

High temperatures and humidity are favorable conditions for disease emergence.

Management

Planting of treated seed with fungicides can reduce the disease outburst. Use of resistant rice varieties may suppress

the attack. Control of field moisture content also is used as a remedy.

White Tip

Description:

A nematode;

Aphelenchoides besseyi

caused this disease. Leaf tips become white with yellow strips between

diseased and

healthy tissue and leaf edges become white sometimes.

Management

Use of resistant varieties is recommended but resistant varieties are not proved effective and still, a loss in yield

occurs. Storage seed fumigation can reduce the population of the nematode.

Sheath spot

Description:

This is a fungal disease caused by

Rhizoctonia oryzae

. The disease looks like sheath blight but is less severe.

Rice Production Knowledge and Practices for Ensuring Food Security

The lesions appear on leaf blades or on sheaths midway up the tiller. Lesions are oval, cream color or white in the center and

broad dark reddish-

brown margin. The pathogen attacks and deteriorates the culm below the sheath lesion on susceptible

varieties. The weakened culm breaks over

where it was infected.

Management

Fungicides used to control sheath blight are also effective in reducing the sheath spot. Foliar application of

recommended fungicides is done to control sheath spot (e.g. azoxystrobin, propiconazole)

Sheath blight

Description:

The disease is caused by a fungus,

Rhizoctonia solani

, a pathogen of both soybeans and rice. This disease

occurs in all rice

growing areas of the world and it occupies the second place after rice blast in term of causing damage. It

causes severe damage in areas where rice is

intensively cultivated with excessive nitrogen fertilizer application and rapidly spread through irrigation. Alternating narrow bands of reddish-

brown or brown with wide bands of greenish grey, white to tan, appears at the base of leaf blade. Under moist conditions, spreading of lesions from

infection points of leaf sheath may occur. Fungal survival structure formed on the leaf surface is called sclerotia. Bird nest area of dead tissue may form

under

favorable conditions.

Management

Foliar application of appropriate fungicides (e.g. azoxystrobin, propiconazole, trifloxystrobin and propiconazole, iprodine) is carried out

to control sheath blight. Higher rates of these fungicides are recommended when the attack is severe. Normally two applications, one at the time of early

internodes elongation and second at 10-14 days after panicle emergence,

are required to control this disease. Excessive nitrogen application

increases the susceptibility to disease, avoiding the

excessive application of nitrogen fertilizer to plants decrease the susceptibility to disease. Seed

treatment with trifloxystrobin

or azoxystrobin or carboxin + thiram is also used to control sheath blight.

Sheath blotch

Description:

This fungal

(Pyrenochaeta oryzae

) disease distresses the leaf sheaths, especially the flag leaf sheath near

the collar. The lesion

starts usually at the sheath edge and expands to form a rhombus blotch that increases in size and it

eventually covers the whole sheath. The lesion is

generally restricted and turns out to be in a zonate form. This discriminates

it from sheath rot.

Management

This disease is normally not severe or widespread enough to warrant control measures.

Sheath rot

Description:

Sarocladium oryzae

is the causative agent of this disease. Symptoms appear during the booting stage on the leaf sheath in which

young panicles are enclosed. Irregular oval-shaped spots with brown centers and a diffuse reddish- brown margin appear. This disease causes

partial emergence of panicle, grain discoloration and white powdery growth

inside of the sheath.

Management

Usually, the fungicidal spray is recommended but fungicides showed little effect on these pathogens. Fungicidal sprays help to lessen the

damage in a disease management process, but it was observed that many bacteria also sow similar

symptoms on rice plant.

Crown sheath rot

Description:

A fungus,

Gaeumannomyces graminis

var.

graminis

, is the causative agent of crown sheath rot. It is also called

Arkansas foot rot,

brown sheath rot, and black sheath rot. Mycelial mats of reddish-brown color are formed in the inner

side of infested sheaths. Dark perithecia are

formed on the sheath. This disease can be easily muddled with stem rot. Under

severe conditions, lodging occurs.

Rice Production Knowledge and Practices for Ensuring Food Security

Management

As this fungus survives on plant residues and is wind-borne in moist conditions, management practices do not work for this disease.

However, foliar application of appropriate fungicides (e.g. azoxystrobin) is somewhat effective in controlling

this epidemic.

Stem Rot

Description:

Fungus (

Sclerotium oryzae

) subsists even after harvest in crop residues and fruiting bodies and then they

are brought to the

soil surface due to flooding and they infect leaf sheaths. Infested soil helps the organism for its survival.

Symptoms generally start to appear at

tillering or initial stage jointing growth. Black angular lesions appear on leaf sheath. These lesions expand and start to blight leaf sheaths from inside

and then culm starts to rot. Culms have black or dark brown

streaks. At maturity, culms may collapse and black round sclerotia form in dead tissues.

This infection can cause unfilled

panicles, plants lodging and death of tillers.

Management

Avoid excessive nitrogen fertilizer application. Try to apply nitrogen in split doses. In potassium deficient soils,

potassium application

will decrease the disease severity. An important agronomic practice is burying of crop residues in the

soil after harvest. Growing resistant rice

varieties is also helpful to reduce disease susceptibility. Stem rot does not cause

damage to early maturing varieties. Fungicides (trifloxystrobin and

propiconazole) are applied as a foliar spray. Higher rates of fungicides are applied in case of disease severity. These fungicides are not applied after

seedhead emergence. Destroy the sclerotia by tillage, by burning the stubbles and by crop rotation. Use of antagonistic organisms also helps to reduce

the

damage.

Tungro disease

Description:

A virus, Rice tungro bacilliform virus (RTBV), is the causative agent of tungro disease. It is the severely

destructive rice virus in

South Asia and Southeast Asia. Leafhoppers spread this virus. Plants are stunted and change color from green to yellow then orange. Numbers of tillers

are reduced, and brown colored lesions appear on the leaf. Leaves are

striped, mottled or show inter-venial necrosis.

Management

To control the tungro virus, many rice resistant varieties have been used and controlled the disease effectively. But intensive farming has

collapsed the impact in some potent leafhopper strain. In Indonesia, this virus is controlled effectively

by obtaining synchronous plant development

through scheduling the planting time and practicing crop rotation with

resistant varieties. To reduce the chances of virus infection, rice seedlings

should be cultured far away from areas where rice

virus diseases occur every year.

Grassy stunt

Description:

It is a viral disease (Rice grassy stunt virus (RGSV)) and transmitted by leafhoppers. It is pervasive in rice

cultivated areas of South Asia, Southeast Asia, Japan, China, and Taiwan.

This virus causes narrow yellow or pale green leaves. Dark brown irregular blotches appeared on leaves. On newly

unfolded leaves, the

striped or mottled pattern appears. Plant growth is stunted and few or no panicles produced.

Management

Suitable insecticides spray can reduce infestation by decreasing the vector populations. A spray of fenthinon or

phosphamidon or

monocrotophos helps to control the damage. Many rice resistant varieties to the leafhopper vectors have developed but leafhoppers have overcome

the resistance in some countries due to a favorable environment for virus vectors.

To reduce the chances of virus infection, rice seedlings should be

cultured far away from areas where rice virus diseases

occur every year.

Bacterial panicle blight

Description: It is caused by bacteria, Burkholderia gladioli, and Burkholderia glumae. Lesions are formed on flag leaf sheath

Rice Production Knowledge and Practices for Ensuring Food Security

that extends to leaf collar. The lesion is discretely having a necrotic and gray color in the center with reddish-brown border.

The lesion length may reach several inches. The panicle may have unfilled or aborted florets.

Management

Avoiding excessive nitrogen application helps to reduce the damage caused by this disease. Early planting can

reduce disease by

escaping the favorable period of disease attack. Some rice varieties are partially resistant while most are susceptible to disease. An important control

measure is to not plant infected seed from previous year seriously affected rice

fields. To test seed lots, the procedure has been developed but they

are not widely available. No pesticides are currently

recommended to control this disease.

Downy mildew

Description:

Causative agent of downy mildew is a fungus called

Sclerophthora macrospora

. Due to mildew, panicles do not

come out of the leaf

sheath and become irregular and twisted. Their size remains small with no seeds.

Management

This disease is extremely rare. No control measures are recommended.

Grain Spotting or Pecky Rice

Description:

The fungus infects the developing grain and causes discoloration of the kernels or hulls. Rice stink bug also

cause kernel

discoloration. Kernel discoloration caused by fungal infections or insect damage is called pecky rice. Single or several florets/panicles appear with

reddish-brown spots. Grain discolored due to fungal growth and stink bugs feedings.

Similar symptoms also appeared by high winds at early

heading stage.

Management

Management practices used to control stink bugs reduces the extent of this disease

Kernel smut

Description:

It is a fungal disease, caused by

Neovossia barclayana.

It is distributed in all rice growing areas. Symptoms

appeared shortly

before maturity. A black smut spores mass replaces a part or all of the grain endosperm. In an ear, few grains are affected partially or wholly. If

severe infestation not occurs, seeds germinate but seedling growth is stunted.

Management

Use of healthy seed, sowing of resistant and early maturing varieties, collection and burning of diseased ear heads and avoid threshing and

winnowing of the diseased crop in the field are useful agronomic practices. Nitrogen application in split doses is recommended. At booting stage,

fungicide applications can be effective for controlling this disease. Seed

treatment with suitable chemicals is used in many rice growing areas.

False smut

Description:

The causative agent of this disease is

Ustilaginoidea Virens

. It is usually a minor disease but it causes an epidemic

sometimes in many

rice cultivating areas. Large orange fungal fruiting structure appears on rice grains panicle. The orange

membrane of this orange fruiting structure

bursts and a mass of spores is exposed. These spores turn dark green to black

with time and grain is then replaced by fungal structure

sclerotia.

Management

Seed treatment is recommended. Seeds are treated with hot water at 52

C for 10 min. Field sanitation helps a lot in reducing the chances

of disease occurrence. Keep the rice field and its surrounding clean. Roughing of infected plants

from the field is suggested in some rice growing

areas. Use of resistant varieties is helpful in some areas. Maintain moisture content in the field by alternate wetting and drying process. As increased

nitrogen application increases the incidence of the disease, balanced amount of fertilizer should be applied. Recommended fungicides application

at booting can hinder the

disease.

Rice Production Knowledge and Practices for Ensuring Food Security

Black Kernel

Description:

The fungus,

Curvularia lunata,

causes black kernel disease. Severe discoloration of grains occur, and kernels appear black after

milling. In case of severe infection, the fungus can cause weakened seedlings or seedling blights.

Management

Use of the right amount of fertilizer, maintaining good soil drainage, hatch layer management, and soil compaction reduction are effective

agronomic practices for the reduction of black kernel disease. Proper insect (stink bug), nematode and fungus control practices help to reduce the

damage. Seed treating for managing other diseases will diminish the seedling

damage. No other management measures are necessary.

Bakanae Disease

Description:

The causative agent of Bakanae disease is

Fusarium moniliforme

, also called white stalk disease and distributed

in all rice growing

areas. Contaminated seedlings are chlorotic, thin and sometimes die when they are transplanted. In the field, leaves of affected plants die out in short

time and plants have only a few tillers. Live plants have unfilled panicles. Many affected plants sometimes become elongated. Abnormal elongation of

these infested plants in the field and in seedbed is a

common disease symptom.

Management

Cultivation of resistant varieties and seed treatment with effective chemicals helps to reduce the damage caused by this disease. Do not plant

the infected seed that comes from an infected field. Stubble destruction of the previous crop either

by plowing or uprooting of infected plants before

sowing. Biological control is also available for the control of

Gibberella sp.

Biological product namely Tri-Cure (

Trichoderma harzianum

isolate

MIT04), is used mainly in Africa.

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In-Silico Analysis of R-Genes in Rice for New Insights of Partial and Complete Resistance Against Bacterial Leaf Blight Disease

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Apr 2025

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Full-text available

Jan 2024

Article History Rice, a staple food for a significant portion of the global population, faces substantial yield losses due to insect pests. These losses, estimated to be between 25 to 50%, pose a serious threat to food security, particularly in developing countries. Insectary plants play a crucial role in conservation biological control programs by providing essential resources such as shelter, food, and oviposition sites for beneficial insects. These resources are particularly important for omnivorous predators, which require both prey and plant materials for their survival and reproduction. Sweet Alyssum (Lobularia maritima), a flowering plant known for attracting beneficial insects, can potentially enhance biological control in rice agroecosystems. By attracting and providing resources for these natural enemies of pests, Sweet Alyssum can contribute to regulating pest populations and reducing the need for chemical pesticides. The mechanisms through which Sweet Alyssum enhances the presence of beneficial insects include the emission of floral volatiles, which act as attractants, and the production of nectar, which serves as a food source for adult insects. Incorporating Sweet Alyssum into integrated pest management (IPM) strategies, such as implementing flower strips, intercropping, or border cropping, can significantly enhance the diversity and abundance of parasitoids and predators in agroecosystems. This, in turn, substantially impacts pest control efficacy, highlighting the potential of Sweet Alyssum as a valuable tool for sustainable and environmentally friendly pest management in rice cultivation. This integration aligns with the growing emphasis on sustainable and regenerative agriculture, offering a pathway towards a more balanced and resilient agricultural landscape.

Research on Intelligent Recognition for Plant Pests and Diseases Based on Improved YOLOv8 Model

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Jun 2024

Plant pests and diseases are important parts of insect disease control and the high-quality development of agriculture. Traditional methods for identifying plant diseases and pests suffer from low accuracy and slow speed, while the existing machine learning methods are constrained by environmental and technological factors, leading to low recognition efficiency. To address the issue of the above problems, this paper has proposed an intelligent recognition algorithm based on the improved YOLOv8 model, which has high recognition accuracy and speed. Firstly, in the Backbone network, the Global Attention Mechanism (GAM) is adopted to weigh the important feature information, thereby improving the accuracy of the model. Secondly, in the mixed feature part of the Neck network, the Receptive-Field Attention Convolutional (RFA Conv) operation is used instead of standard convolution operations to enhance the processing ability for feature information and to reduce computational complexity and costs, thus improving the network performance. After verifying the rice and cotton datasets, the accuracy indicator mean average precision (mAP) reaches 71.27% and 82.91%, respectively, in the two different datasets. Comparing these indices with those of the Faster R-CNN, YOLOv7, and the original YOLOv8 model, the results fully demonstrate the effectiveness and superiority of the improved model in terms of detection accuracy.

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The rice leaf folder (Cnaphalocrocis medinalis) is a significant pest affecting rice cultivation worldwide, c ausing considerable yield losses and economic damage. This review provides a comprehensive examination of the lif e cycle of the rice leaf folder, highlighting the developmental stages from egg to adult and the factors influencing its population dynamics. Emphasis is placed on understanding the biology and ecology of this pest to inform effective m anagement strategies. Biological control methods, including the use of natural predators, parasitoids, and entomopath ogenic organisms, are critically evaluated for their efficacy and sustainability. Additionally, integrated pest managem ent (IPM) strategies combining biological, cultural, and chemical controls are discussed, offering a holistic approach to mitigating the impact of rice leaf folder infestations. The review underscores the importance of continuous monito ring, farmer education, and the adoption of environmentally friendly practices to achieve sustainable pest manageme nt. Future research directions are proposed to address current knowledge gaps and improve control measures, ultimat ely enhancing rice production and food security.

Prey Record of Various Predators

Chapter

Nov 2023

Many field studies reveal the predator’s prey record, which is available in Chap. 2. However, for the easy understanding of international readers, in this chapter, a list of predator’s names, its family, location, prey record, its stage preference with citations are presented in Tables 14.1, 14.2, 14.3, 14.4, 14.5, 14.6, 14.7, 14.8, 14.9, 14.10, 14.11 and 14.12 below.

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Fungus gnats (Sciaridae) are one of the most devastating pests on mushroom farms. Generally, they are controlled using relatively inefficient physical means, like sticky or pheromone traps, or with chemical pesticides. Here, we have proposed an integrated fungus gnat control system combining a UV-A LED source at 365 nm and a high-power laser diode at 445 nm. The 365 nm UV-A LED serves a light trap, since previous studies have concluded that fungus gnats show maximum attraction in the range of 365–390 nm. The UV-A LED is also modulated at different frequencies, and the response of the gnats corresponding to these different frequencies was observed. We utilized an Arduino Uno microcontroller to run the integrated device, and a BASLER USB camera was used to capture the images. Our experiments indicated that a frequency of 40 Hz is the optimal choice for attracting the gnats most rapidly. Within 20 s of exposure, the UV-A LED operated at 40 Hz was found to trap approximately 80% of the gnats. In a restricted trapping zone measuring 2.5 × 2.5 × 3 cm³, our integrated module, which includes a 40 Hz modulated UV-A LED and a laser, resulted in a survival rate of only 50% for the total number of gnats. This outcome was accomplished through periodic 200 ms long exposures, amounting to a total duration of 2 min for a group of 100 gnats.

Future grain crops

Chapter

Jan 2022

Climate change has had devastating effects on agriculture, industry, and food security. The recent outbreak of the Covid-19 pandemic has exacerbated this situation as tons of crops have had to be destroyed due to the global closure of retail outlets. This raises questions on the world’s preparedness to deal with pandemics without ceasing food production and distribution. Most staple foods comprise grain crops; therefore, feeding the ever-increasing global population means increasing production of these crops. There is a need for drought, pest, and disease-resilient crops that are nutritionally superior and health-promoting. Future grain crops need to be produced in a cost-effective, sustainable, and environmentally conscious way. Therefore, some innovative farming methods need to be explored. The future of agriculture, therefore, conceivably lies in the use of artificial intelligence, less reliance on agricultural chemicals as well as carbon-emitting fuels, hydroponics, and short-season cultivars, among others.

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Article

Full-text available

Dec 2017
FIELD CROP RES

High resource availability can reduce anti-herbivore resistance (a plant's ability to defend against herbivores and reduce damage) in rice, Oryza sativa L, but may also increase tolerance (a plant's ability to withstand damage by, for example, compensatory growth). Through a series of greenhouse, screenhouse and field experiments, this study examines fitness (survival and development × reproduction) of the brown planthopper, Nilaparvata lugens (Stål), on resistant (IR62) and susceptible (IR22) rice varieties and age-related rice tolerance to planthopper damage under varying resource (nitrogenous fertilizer) availability. Planthoppers reared on IR62 in the greenhouse had lower fitness than planthoppers on IR22. IR62 became increasingly resistant as plants aged. IR22 was generally more tolerant of planthopper damage, and tolerance increased in IR22, but declined in IR62, as the plants aged. Rice plants infested at pre-tillering stages (3-4 leaf stage) in the screenhouse had greater losses to root, shoot and grain yield per unit weight of planthopper than plants infested at tillering stages, particularly in IR22. These trends were mainly due to the impact of planthoppers during pre-tillering stages and the length of exposure to the planthoppers. High nitrogen compromised IR62 resistance, particularly in tillering plants in the greenhouse study; however, high nitrogen did not increase planthopper biomass-density on IR62 in greenhouse or field cages. Tolerance to damage in IR62 at mid-tillering stages declined under increasing levels of nitrogen, but nitrogen increased tolerance during late-tillering stages. Planthopper damage to IR22 in field cages was severe and hopperburn (plant death) occurred in 83% of IR22 plants under high nitrogen (60-150 kg N ha −1). In contrast, despite planthopper infestations, damage to IR62 was low in field-grown plants and productivity (tillers, roots, shoots and grain) increased in IR62 under increasing nitrogen. Our results indicate that, whereas nitrogenous fertilizer increases planthopper fitness on susceptible and resistant varieties, the net effects of high nitrogen on IR62 include decreased planthopper biomass-density (apparent in all experiments) and higher tolerance to damage during later growth stages (observed in the greenhouse, and during one of two seasons in field cages).

Recent progress on the genetics and molecular breeding of brown planthopper resistance in rice

Article

Full-text available

Jun 2016

Brown planthopper (BPH) is the most devastating pest of rice. Host-plant resistance is the most desirable and economic strategy in the management of BPH. To date, 29 major BPH resistance genes have been identified from indica cultivars and wild rice species, and more than ten genes have been fine mapped to chromosome regions of less than 200 kb. Four genes (Bph14, Bph26, Bph17 and bph29) have been cloned. The increasing number of fine-mapped and cloned genes provide a solid foundation for development of functional markers for use in breeding. Several BPH resistant introgression lines (ILs), near-isogenic lines (NILs) and pyramided lines (PLs) carrying single or multiple resistance genes were developed by marker assisted backcross breeding (MABC). Here we review recent progress on the genetics and molecular breeding of BPH resistance in rice. Prospect for developing cultivars with durable, broad-spectrum BPH resistance are discussed.

Dynamics of predators in rice canopy and capacity of natural control on insect pests in paddy fields with different nitrogen regimes

Article

Full-text available

Jan 2006

Use of Chemical Fungicides for the Management of Rice Blast (Pyricularia Grisea) Disease at Jyotinagar, Chitwan, Nepal

Article

Full-text available

Sep 2015

Rice blast caused by Pyricularia grisea Sacc. is the important disease of rice and different fungicides against this disease were evaluated in summer 2014 at Karma Research and Development Center, Jyotinagar, Chitwan, Nepal. A susceptible rice cultivar ‘Mansuli’ was planted in randomized complete block design and fungicides viz. Tricyclazole 22% + Hexaconazole 3% SC (0.2%), Streptomycin 5% + Thiophanate Methyl 50% WP (0.15%), Prochloraz 25% EC (0.3%), Kasugamycin 2% WP (0.2%), Hexaconazole 4% + Zineb 68 % WP (0.2%) and Udaan (Hexaconazole 3% SC) (0.2%) were sprayed thrice at weekly interval starting from the booting stage. All these fungicides were found to be effective in controlling leaf and neck blast disease as compare to control one. Among them, Tricyclazole 22% + Hexaconazole 3% SC was found to be the most effective with least leaf blast severity (6.23%), neck blast incidence (8.97%), and highest percentage disease control (87.08% and 79.62% in leaf blast and neck blast respectively) and grain yield (4.23 t/ha) followed by Prochloraz 25% EC (0.3%) and Udaan (Hexaconazole 3% SC) (0.2%). It is therefore concluded that Tricyclazole 22% + Hexaconazole 3% SC fungicide could be used to control rice blast at weekly interval starting from the booting stage for three times. Int J Appl Sci Biotechnol, Vol 3(3): 474-478

Selection of Nectar Plants for Use in Ecological Engineering to Promote Biological Control of Rice Pests by the Predatory Bug, Cyrtorhinus lividipennis, (Heteroptera: Miridae)

Article

Full-text available

Sep 2014
PLOS ONE

Ecological engineering for pest management involves the identification of optimal forms of botanical diversity to incorporate into a farming system to suppress pests, by promoting their natural enemies. Whilst this approach has been extensively researched in many temperate crop systems, much less has been done for rice. This paper reports the influence of various plant species on the performance of a key natural enemy of rice planthopper pests, the predatory mirid bug, Cyrtorhinus lividipennis. Survival of adult males and females was increased by the presence of flowering Tagetes erecta, Trida procumbens, Emilia sonchifolia (Compositae), and Sesamum indicum (Pedaliaceae) compared with water or nil controls. All flower treatments resulted in increased consumption of brown plant hopper, Nilaparvata lugens, and for female C. lividipennis, S. indicum was the most favorable. A separate study with a wider range of plant species and varying densities of prey eggs showed that S. indicum most strongly promoted predation by C. lividipennis. Reflecting this, S. indicum gave a relatively high rate of prey search and low prey handling time. On this basis, S. indicum was selected for more detailed studies to check if its potential incorporation into the farming system would not inadvertently benefit Cnaphalocrocis medinalis and Marasmia patnalis, serious Lepidoptera pests of rice. Adult longevity and fecundity of both pests was comparable for S. indicum and water treatments and significantly lower than the honey solution treatment. Findings indicate that S. indicumis well suited for use as an ecological engineering plant in the margins of rice crops. Sesame indicum can be a valuable crop as well as providing benefits to C. lividipennis whilst denying benefit to key pests.

Field efficacy of fungicides for management of sheath blight and narrow brown leaf spot of rice

Article

Feb 2018
CROP PROT

Sheath blight (caused by Rhizoctonia solani AG1-IA) and narrow brown leaf spot (NBLS, caused by Cercospora janseana) are among the most important diseases affecting rice production in Texas and in other regions in the southern United States. Strobilurin fungicides have been used extensively to manage these two diseases, especially sheath blight. Unfortunately, heavy reliance on use of fungicides with a single mode of action has induced the development of the strobilurin-resistant isolates of R. solani AG-1 IA in the U.S. NBLS, once considered a minor disease in the U.S, is growing in its occurrence and severity, while little scientific information is available on NBLS management. This created an urgent need for identifying other effective fungicides with different modes of action. A 6-year field study was conducted on rice to evaluate the efficacy of newly registered and unregistered fungicides in comparison to common fungicides for management of sheath blight and NBLS diseases. Single applications of the fungicides containing azoxystrobin, propiconazole, azoxystrobin plus propiconazole, trifloxystrobin plus propiconazole, fluxapyroxad, pyraclostrobin, flutolanil and antibiotics (validamycin and kasugamcyin) were made at the late booting stage. Sheath blight and NBLS severities were rated prior to harvest. All the fungicide treatments were effective in reducing sheath blight severity compared to the untreated control in each year. Propiconazole and fluxapyroxad were more effective in reducing NBLS than other fungicides. Along with reduced sheath blight and NBLS severities, fungicide-treated plots had higher yields than untreated plots.

Improvement of yield, pest control and Si nutrition of rice by rice-water spinach intercropping

Article

Jul 2017
FIELD CROP RES

Intercropping is an effective agricultural practice for crop production, resource utilization, and pest control. However, aquatic crops (e.g., rice) intercropping is relatively rare. Field experiments of two years/four seasons (early and late seasons in 2012, 2013) was carried out to test the effects of rice-water spinach intercropping on yield, disease and pest control, and Si, N nutrition of rice plant in the present study. The experiment contained three treatments including rice monoculture, water spinach monoculture and rice-water spinach intercropping with three replicates by randomized block design. Results showed that rice-water spinach intercropping significantly reduced the incidence of disease and pest of rice, with a reduction of rice sheath blight by 17.3%–50.6% and rice leaf folders by 5.1%–58.2%. For yield, intercropping resulted in an increase of rice yield by 45.1%–71.7% in early season and 20.9%–34.3% in late season, but a decrease of water spinach yield by 14.1%–37.1% in early season and 3.8%–18.3% in late season. However, rice-water spinach intercropping gave a higher land equivalent ratio (1.02–1.17) therefore improved land utilization efficiency. Furthermore, intercropping significantly increased Si concentration, Si and N absorption in rice leaves in ripening stage compared with rice monoculture. Our findings suggest that rice-water spinach intercropping exhibits yield advantage for rice or total yield, improves Si nutrition of rice and provides an environmentally sound approach in controlling disease and pest.

Thiamethoxam seed treatment for control of rice thrips ( Chloethrips oryzae ) and its effects on the growth and yield of rice ( Oryza sativa )

Article

Aug 2017
CROP PROT

Rice thrips (Chloethrips oryzae Williams) is one of the key pests of rice (Oryza sativa L.), and is usually controlled by labor-intensive foliar sprays of agrochemicals under field conditions. To reduce labor intensity and increase the utilization of agrochemicals, thiamethoxam seed treatment was studied as a simple and accurate control technology for C. oryzae. Field plot experiments were conducted to investigate the control efficacy of three methods of thiamethoxam seed treatment for C. oryzae, and their effects on growth and yield of rice in 2014–2016. Excellent control of C. oryzae was achieved using thiamethoxam 350 FS (flowable concentrate for seed treatment) seed treatment at a rate of 70 g ai/100 kg of seeds, at 17–28 days after sowing. Better control of leaf-tip rolling was observed when for seed treatment application rice seeds were soaked firstly in water for 8–10 h and then dried at room temperature, then coated with thiamethoxam 350 FS solution, soaked again in water and germinated (method A) or when rice seeds were coated firstly with thiamethoxam 350 FS solution, soaked in water and germinated (method C) than when rice seeds were soaked firstly in water for 8–10 h and then plus thiamethoxam 350 FS solution, then soaked again in water and germinated (method B). Field observations indicated that thiamethoxam seed treatment at this rate had no negative effects on the timing or percentage of seedling emergence, establishment, and key seedling characteristics including plant height, root length, and fresh above-ground and underground weight. However, rice yields of thiamethoxam seed treatment were increased significantly compared to untreated control. These results suggested that treatment of rice seeds by thiamethoxam using the method A or C was more effective against C. oryzae than using the method B for up to 28 days after sowing under field conditions. Use of thiamethoxam seed treatment was not phytotoxic to rice and represents an important alternative for C. oryzae management in the crop.

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