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Locust and Grasshopper Management

  • Independant consultant in locust ecology and control

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Locusts and grasshoppers (Orthoptera: Acridoidea) are among the most dangerous agricultural pests. Their control is critical to food security worldwide and often requires governmental or international involvement. Although locust and grasshopper outbreaks are now better controlled and often shorter in duration and reduced in extent, large outbreaks, often promoted by climate change, continue to occur in many parts of the world. While some locust and grasshopper control systems are still curative, the recognition of the damage these pests can cause and the socioeconomic consequences of locust and grasshopper outbreaks have led to an increasing paradigm shift from crop protection to preventive management. We are far now from a system of all-chemical control that D.L. Gunn wrote about in his review in 1960 (Annu. Rev. Entomol. 5:279–300). Effective preventive management strategy nowadays relies on an improved knowledge of the pest biology and ecology and more efficient monitoring and control techniques.
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EN64CH02_ZhangL ARI 24 November 2018 11:21
Annual Review of Entomology
Locust and Grasshopper
Long Zhang,1,Michel Lecoq,2
Alexandre Latchininsky,3,4 and David Hunter5
1China Agricultural University, Beijing 100193, China; email:
2CIRAD, 34398 Montpellier, France; email:
3University of Wyoming, Laramie, Wyoming 82071, USA
4Current affiliation: Food and Agriculture Organization of the UN, 00153 Rome, Italy;
5Orthopterists’ Society, McKellar, ACT 2617, Australia; email:
Annu. Rev. Entomol. 2019. 64:15–34
First published as a Review in Advance on
September 26, 2018
The Annual Review of Entomology is online at 011118-
Copyright c
2019 by Annual Reviews.
All rights reserved
Corresponding author
locust, grasshopper, outbreak, monitoring and forecasting, preventive
management strategy
Locusts and grasshoppers (Orthoptera: Acridoidea) are among the most dan-
gerous agricultural pests. Their control is critical to food security worldwide
and often requires governmental or international involvement. Although lo-
cust and grasshopper outbreaks are now better controlled and often shorter
in duration and reduced in extent, large outbreaks, often promoted by cli-
mate change, continue to occur in many parts of the world. While some
locust and grasshopper control systems are still curative, the recognition of
the damage these pests can cause and the socioeconomic consequences of
locust and grasshopper outbreaks have led to an increasing paradigm shift
from crop protection to preventive management. Effective preventive man-
agement strategy relies on an improved knowledge of the pest biology and
ecology and more efficient monitoring and control techniques.
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Locust: type of
grasshopper with a
remarkable and
potentially devastating
form of density-
dependent phase
polyphenism forming
adult swarms and/or
nymphal bands
Outbreak: marked
increase in locust
numbers due to
multiplication, and
Recession: period
without widespread
and heavy infestations
by swarms
Since the beginning of civilization, locusts and grasshoppers have been among the most devastating
threats to agriculture. This group of insects contains hundreds of pest species and affects the
livelihoods of one in every ten people worldwide (74). Locusts and grasshoppers are profoundly and
qualitatively different from other pests: Their populations can quickly grow to catastrophic levels,
and some species form very dense bands and swarms that can cause a great deal of damage in a very
short time. Their swarms can migrate hundreds of kilometers per day and invade areas covering
millions of square kilometers, resulting in major economic, social, and environmental impacts on
an international scale (Figure 1). The consequences of the invasions can be disastrous for both
the food security and livelihoods of the rural populations in affected areas. Control campaigns
commonly cost many millions of dollars (7), and the large amounts of chemical insecticides used
can have serious side effects on the environment.
Locust and grasshopper outbreaks can be chronic (e.g., grasshoppers in the African Sahel and
grasshoppers/locusts in China) or episodic (e.g., desert locust and many other locusts) where there
are alternating periods of invasion and recession. These pests have been fought for more than a
thousand years (47). However, in the past half century, locust and grasshopper control has made
progress through better knowledge of their biology and ecology, more efficient monitoring, and
more environmentally sound control strategies and with the development of biological products
and the increasing use of high-level technologies such as satellite imagery and geographic infor-
mation systems. During this period, several huge locust invasions triggered intensive international
research efforts to develop alternatives to synthetic insecticides that are less environmentally haz-
ardous along with improved control strategies and early warning systems (54, 65).
We are far now from a system of all-chemical control that Gunn (46) wrote about in his
review almost 60 years ago. Locust and grasshopper control is increasingly rational and based on
Figure 1
Locust (Locusta migratoria) swarm migrating over rangeland during August 2011 in Southern Russia.
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Plague: period of one
or more years of
widespread and heavy
infestations of locust
bands or swarms
a geospatially based risk assessment, with analysis of the effects of treatments on humans and the
environment becoming an essential part of most treatment programs. Management of outbreaks
is much improved with the frequency of outbreaks often reduced, and preventive strategies have
resulted in much-reduced damage to crops and livelihoods and less side effects on the environment.
This article reviews the advances made in recent years as well as areas where further improvement
is required if we are to manage the locust and grasshopper problem even more effectively.
There are more than 500 species of acridids (Orthoptera: Acridoidea) that can cause damage to
pastures and crops (13), and about 50 are considered major pests. Although locust outbreaks are
now better controlled and invasions are often shorter and reduced in extent, large outbreaks—of
both locusts and grasshoppers—continue to occur in many parts of the world. The largest recent
outbreaks have included two desert locust (Schistocerca gregaria) invasions covering a large part of
Africa and southwest Asia from 1986 to 1989 [area treated/protected was 16.8 million hectares (ha)
and cost of control was US$274 million] (60, 129) and from 2003 to 2005 (13 million ha, US$500
million) (7) and two invasions of the migratory locust, Locusta migratoria, in Madagascar from 1997
to 2000 (4.2 million ha, US$50 million) (78, 80) and 2013 to 2016 (2.3 million ha, US$37 million)
(41). There were also large-scale infestations in Eurasia of the Italian locust Calliptamus italicus in
2000 (Kazakhstan; 8.1 million ha, US$23 million) (72) and of the Italian locust with some Moroccan
locusts, Dociostaurus maroccanus, in 2014 (the Caucasus and central Asia; 6.7 million ha) (37); large
outbreaks of Chortoicetes terminifera in eastern Australia in 2010 (1.1 million ha, US$50 million)
(103); and large outbreaks of various grasshoppers in the United States between 1986 and 1988
(8.2 million ha, US$75 million) (88) and in 2010 (Wyoming; 2.4 million ha, US$7.4 million) (101).
Some have suggested that the huge costs of these large-scale treatment programs, often due to
inefficient use of control resources, outweigh the benefits (63). One reason for the uncertainty of
the damage caused consists of difficulties in assessing damage to crops in remote areas (64), and
another complicating factor is that while the costs are reported in US dollars, the benefits are often
in a local currency that is of much lower value, reducing the apparent value of crops saved. However,
benefits and costs of locust and grasshopper control are increasingly better understood (92, 105). It
was estimated that the 1984 plague of the Australian plague locust, Chortoicetes terminifera, would
have caused US$82 million damage if it had not been controlled. The actual damage was only
US$4 million, so that the US$2.7 million cost of control returned a net benefit of 29:1 (148).
A more recent Australian study showed that concerted control operations conducted by state
and national government agencies as well as landholders from 2010 to 2011 had a net benefit of
US$963 million. As such, control operations costs of about US$50 million resulted in a benefit-
cost ratio of over 18:1 (103). In studies where only damage was assessed, an outbreak of the Italian
locust Calliptamus italicus in Kazakhstan in 1999 resulted in estimated damage to crops of US$15
million (72). In North America, every year, grasshoppers destroy 21–23% of rangeland vegetation,
causing US$1.25 billion in monetary losses (10, 52). Brader et al. (9) reported that, in Africa in
2004, the desert locust caused crop losses of >80% in Burkina Faso, Mali, and Mauritania, with
8 million people affected and many households requiring food aid. Losses to crops and pastures are
very disruptive and lead to further effects such as having to sell animals at low prices to meet the
subsistence needs of households. Furthermore, the negative income shock may have a long-term
impact on the educational outcomes (school enrollment and completion) of children living in rural
areas (29).
Losses due to locusts and grasshoppers are not limited to damage to pastures and crops. The
rapid loss of vegetation cover may result in soil erosion and increased runoff. Outbreak populations Locust and Grasshopper Management 17
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(control) strategy:
strategy aiming to
treat as many locust or
grasshopper hot spots
as possible before they
damage crops, with
treatments beginning
early in outbreaks
Outbreak area:
limited regions where
significant outbreaks
have occurred and
given rise to upsurges
and invasions
Hopper band/adult
swarm: group of
gregarious hoppers/
adults, of high density,
that can move in a
coherent manner
destroy food sources for many animals and thus affect biodiversity; such effects may be particularly
pronounced in isolated insular ecosystems (68). And large-scale control programs can also affect
biodiversity, including that of nontarget grasshoppers and other arthropods (32, 118, 119, 130).
However, at moderate densities, locusts and grasshoppers are an essential component of a
healthy rangeland ecosystem (8) in that they stimulate plant growth and participate in nutrient cy-
cling and the food chain (74). Therefore, management does not aim to eradicate them but decrease
their densities below economic thresholds: For grasshoppers, a 70–80% population reduction is
usually sufficient for maintaining sustainable rangeland forage production (71, 115). Obviously,
with locusts, whose densities often exceed hundreds and even thousands per square meter, the
desired level of control is higher, especially near crops, where it is commonly 95–98% (72).
While locust and grasshopper treatments are sometimes left to landholders protecting their crops,
as occurs with many other pests, most countries recognize that effective management requires
government intervention because the intense treatment programs are beyond the capabilities of
landholders alone. This is certainly true for locusts that can migrate and invade previously unin-
fested areas in such high densities that they can overwhelm crop protection efforts of landholders
and destroy their crops within days. Even grasshoppers readily move from one farm to another, so
their treatment is often considered a community responsibility, involving at least some government
input (101).
In the past, management programs were largely curative, and while some still are, the recog-
nition of how damaging locusts and grasshoppers can be has led to a paradigm shift from crop
protection to preventive management of these pests (5, 54, 97, 151). Preventive management
strategies are increasingly implemented as being the most rational, effective, economically feasi-
ble, and environmentally sound methods of control. Preventive management aims to treat as many
locust or grasshopper hot spots as possible before they can damage crops by intervening early in
outbreaks, as suggested by Uvarov (141). Some of the most successful preventive management
programs have been with species where population growth early in outbreaks is largely limited
to localized outbreak areas that are particularly favorable for breeding. For locusts having such
outbreak areas, Uvarov (141) proposed that plagues could be prevented by regularly monitoring
and treating populations within outbreak areas to avoid high population increases and subsequent
large-scale escapes into cropping areas. For other locusts with outbreak areas, including the red lo-
cust (Nomadacris septemfasciata) in southern Africa, the African migratory locust (Locusta migratoria
migratorioides), and, until recently, the South American locust (Schistocerca cancellata), plagues were
successfully prevented for many years (43, 56, 97). These early successes relied almost entirely on
the widespread use of broad-spectrum and often cumulative applications of chemical pesticides,
which contrasts with current preventive methods that are more environmentally friendly and are
based on early warning systems and increasingly on the use of both biological and chemical control
applied with more precise spraying techniques.
However, outbreak areas are not always limited in size, and some locusts such as the desert
locust (97, 134) or the Australian plague locust (53, 100) have widespread favored habitats that
cover hundreds of thousands of square kilometers or more. These areas can be remote with
limited access, making detecting initial infestations difficult. Finding and treating small hopper
bands is particularly difficult because they are often not obvious until you are nearly beside them.
Consequently, band infestations are often missed on survey, and even when infestations are found,
their treatment using ground sprayers is slow and time consuming. Symmons (135) insisted that
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Upsurge: period
following a recession
marked by a very large
increase in locust
numbers in
the common method of searching for bands of the desert locust by ground vehicle is unlikely
to be effective because during upsurges, there is not enough staff or vehicles to find and treat a
significant proportion of the locust population. With the Australian plague locust, Hunter et al.
(59) found that in the middle of hot days, bands roost on the vegetation and can be seen by ground
scouts from hundreds of meters, but the areas that need to be surveyed are so large that effective
preventive treatments should rely on using aircraft to locate bands visible from the air.
Swarms are much more visible than hopper bands, but the treatment period is short because
of their highly developed migratory capacity. With the desert locust, swarms can migrate many
hundreds and even thousands of kilometers, making them an international challenge such that
control strategies must then involve strong cooperation between countries with specialized centers
dedicated to this pest (79). This international cooperation extends across 60 countries concerned
by the risk of invasion and is ensured by the Desert Locust Control Committee, which provides
guidance and coordination of actions over the entire range of this pest, from India to Mauritania
(40). However, while preventive management strategies have been implemented in widespread
species such as the desert locust (17, 19, 20, 78, 95, 96) and Australian plague locust (54), and
have often reduced the size of upsurges and plagues, actual plague prevention has not always been
A third common situation is where locusts and grasshoppers are present most of the time and
require regular treatments. With species such as the Senegalese grasshopper, Oedaleus senegalensis
(99), and the variegated grasshopper, Zonocerus variegatus (104), in Africa, the problem is a local
one and so is the responsibility of local plant protection services. Other species, however, are
much more widespread such as those in central Asia and China, where there are regular treatment
programs involving a dedicated workforce that is able to cope when treatment programs increase
in size. In central Asia, there are outbreaks of one or more pest species almost every year, which
has led the Food and Agriculture Organization of the United Nations (FAO) to set up the Locust
Watch program to improve national and international locust management in the Caucasus and
central Asia (37).
For species that occur only occasionally, there has been some debate as to the effectiveness
of preventive strategies (97, 136). During periods when numbers are low, resources are allocated
to more pressing immediate concerns, so when upsurges do occur, adequate resources take time
to become available. As a result, the large-scale treatments required during upsurges are delayed,
allowing pest populations to increase substantially, as occurred with the desert locust in Africa
between 2003 and 2005 (7) and the migratory locust in Madagascar between 2013 and 2016.
However, for the desert locust, the net benefits of a preventive management strategy were shown
to be three times higher than a curative strategy (105). Overall, evidence of the effectiveness of
preventive management strategies is accumulating in that they have often been able to reduce
both the frequency of upsurges and the size of the invasions (78, 97, 134). Even when upsurges
have led to plagues, the plagues generally are more short lived than in the past, meeting the aim
of Uvarov (141) of reducing the size of invasions and damage to crops.
A critical part of preventive management programs is being able to locate significant infestations
rapidly. There is now a much greater understanding of the factors that lead to outbreaks, allowing
their beginning to be recognized and early intervention implemented. The much more rational
organization of both monitoring and control once outbreaks are underway has been instrumental
in making preventive management programs possible. Locust and Grasshopper Management 19
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Phase change:
a reversible transition
process between
solitarious and
gregarious phases in
locusts in response to
changes in population
phenomenon in which
two or more distinct
phenotypes are
produced by the same
4.1. Recent Progress in Understanding Locust and Grasshopper Behavior
While the mechanisms of locust and grasshopper population dynamics, particularly their behav-
iors related to outbreaks, are far from fully elucidated (75, 109), there have been major advances in
recent years. For locusts, there is phase transformation to form bands and swarms during outbreaks
and plagues, but the importance of the solitary phase in population dynamics has been demon-
strated in various species (34, 76, 77, 82). The use of population genetic tools such as molecular
markers has demonstrated that solitary-phase locusts are much more mobile and abundant than
was previously thought, and with the desert locust, migrations of the solitary phase are a key
adaptation for survival in a hostile environment (14). Consequently, there is now an increasing re-
alization that surveys for isolated locusts are important in recognizing the first steps in population
increases leading to outbreaks.
Research on band and swarm behavior has found that the actual factors that lead to the swarming
behavior in locusts vary between species. This is not surprising since the ability to form bands
and swarms has evolved independently a number of times in acridids (131, 132). Desert locust
gregarization is evoked by touching of the femur of the hind legs (122, 123), in that locusts brush
against each other when numbers are high, while Australian plague locust gregarization is triggered
by tactile stimulation of the antennae (22). Tactile stimuli trigger the increase of biogenic amines,
particularly serotonin, in the locust nervous system (1, 116); these amines play critical roles in
the neurophysiology of locust behavioral phase change. The recent comprehensive review by
Cullen et al. (21) details numerous aspects of locust phase polyphenism. In addition to the tactile
responses, there are effects of pheromones on gregarious behaviors such as group oviposition, but
the varying results observed among the locusts studied once again suggest a range of mechanisms
(35, 49, 109, 122, 145).
There are also various explanations as to why gregarious nymphs march. Some studies (6, 48,
124) suggest that when high numbers of nymphs are together, there is substantial cannibalism
that is reduced by nymphs marching away. However, Buhl et al. (11) found that the pursuit/escape
model did not fit well with the marching behavior of the Australian plague locust, in that when
in dense groups, nymphs orientated to, and aligned with, each other as they marched together.
Hunter et al. (58) observed that Australian plague locust nymphs marched forward, toward the
band front (where locusts stop to eat) because nymphs marching forward disturbed increasingly
more locusts, while any nymphs marching back toward areas of lower density disturbed fewer
locusts; their marching was soon overwhelmed by columns of forward-marching nymphs. The
same mechanism may account for the typical rolling flight behavior of low-flying swarms, such as
with Rhammatocerus schistocercoides (82). Recently, Ariel & Ayali (2) provided an overview of locust
collective movement and its modeling.
4.2. Critical Factors Leading to Locust and Grasshopper Outbreaks
Preventive control relies on having a reasonably good understanding of the critical factors that lead
to population increases so that when such conditions occur, preparations can be made for the extra
resources required for survey and treatment. It takes several generations of successful breeding
for initial localized outbreaks to reach plague proportions, and the aim of preventive control is to
rapidly find and treat locusts as early as possible in the breeding sequence. For arid and semiarid
zone species like the desert locust and the Australian plague locust, sequences of regular rainfall
lead to outbreaks several times per decade, but plagues are much less frequent—once a decade
or less. Both species are found over large territories, with some parts of their distribution area
receiving more rain in summer while others receive more rain in winter; studies of migrations,
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including detecting movements using radar have demonstrated that these locusts have a migratory
circuit between summer and winter rainfall areas (19, 27, 30, 80). While there is some evidence for
locusts preferentially migrating on or toward weather systems more likely to produce rain, such
as on fronts or lows for the Australian plague locust (33, 34) or the Intertropical Convergence
Zone for the desert locust (19, 147), often, there is little or no rain as these systems pass through
the semiarid to arid areas these two locusts inhabit and locust populations remain moderate to
low. But occasionally, there is a sequence of rains in both the summer and winter rainfall areas,
and locust numbers increase. However, the summer and winter rainfall areas may be hundreds
or even thousands of kilometers apart, and so locusts need to migrate long distances to reach the
complementary rain areas. Consequently, while a sequence of rains is necessary for a population
upsurge, the actual size of the upsurge (and whether a plague results) also depends on whether
most or only some of the locusts actually reach the rain areas in each generation of a breeding
sequence. A strong locust–precipitation correlation has also been found in the migratory locust
(76, 137) and other species (53, 57).
For some species, the association of outbreaks with rainfall is quite complex. In Indonesia, it
is usually too humid for the migratory locust, but outbreaks in the late 1990s could be explained
by drought associated with the El Ni ˜
no phenomenon (83). For the migratory locust in China and
central Asia, floods followed by dry periods are important for outbreaks in that after floods recede,
large areas of green vegetation become favorable for the locust breeding (69, 133). For Schistocerca
cancellata in Argentina (56) and Austracris guttulosa in Australia (57), upsurges occur when rains
fall at particular times during locust development. During the past several decades, several locust
and grasshopper species were shown to expand their range and increase the number of annual
generations, possibly as a result of climate change (21). With climate having such a dominant role
in population dynamics of many locust species, future changes in climate will undoubtedly have
an impact, but so far, there has been no consensus as to how climate change might affect outbreaks
(18, 86, 102, 139, 149).
For a number of grasshoppers, their population dynamics may not always follow simple climate-
driven models (62), because biotic factors such as natural enemies can be important (74). Re-
cent research has illustrated the complex set of direct and indirect interactions that can underlie
grasshopper population dynamics (4, 15, 62).
There is increasing evidence that human activity may have contributed to outbreaks. Changes
in the environment in West Africa [deforestation, increased cassava cultivation, and the spread
of Asteraceae (Chromolaena odorata)] may be responsible for the increase of the economic impor-
tance of the variegated grasshopper, Zonocerus variegatus (104). Overgrazing is a common cause of
outbreaks for some species such as the Moroccan locust (Dociostaurus maroccanus)inNorthAfrica
and central Asia where sheep create favorable conditions for gregarization (67, 128). For the
grasshopper Oedaleus asiaticus in northern China, heavy livestock grazing and consequent grass-
land degradation promote outbreaks, perhaps by reducing plant protein content (12). In Australia,
Deveson (25) has concluded that swarms of Austroicetes cruciata and Chortoicetes terminifera may
have resulted from the ecological changes that followed the introduction of European livestock
and agriculture.
4.3. Information Support Systems for Improved Monitoring and Forecasting
Monitoring programs aim to determine the extent and location of any significant infestations, in-
cluding higher-density areas suitable for treatment. Traditionally, past timings largely determined
when surveys should be conducted, but increasingly important is the integration of data from many
sources into information support systems to provide forecasts of when and where infestations are Locust and Grasshopper Management 21
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likely to be. When the conditions occur that are conducive to an outbreak of a particular locust
or grasshopper species, survey teams should then be rapidly deployed so that significant infesta-
tions can be located and treated quickly as part of early intervention. Information support systems
generally consist of a geographic information system (GIS), which combines many layers of data
on locusts/grasshoppers and their habitats to provide more accurate forecasts. Many species are
more common in certain types of habitat and high-spatial-resolution (30-m) multispectral images
from Landsat remote sensing satellites have been used to map such habitats for the Australian,
migratory, desert, and Brazilian locusts (23, 100, 127, 143). The green vegetation that results after
rain is important for locust and grasshopper survival and maturation, but rainfall data are often
inadequate because of the limited number of rainfall stations in arid and semiarid zones. Some
programs (desert locust, Australian plague locust) use rainfall interpolation models via meteo-
rological satellites, but there is an increasing use of satellite imagery to detect green vegetation
using the normalized difference vegetation index (NDVI) technique, which can distinguish areas
of green vegetation from bare soil (18, 69). The Desert Locust Information Service of the FAO
also uses MODIS (Moderate Resolution Imaging Spectroradiometer) images at a spatial resolu-
tion of 250 m, consisting of a 16-day composite image of NDVI values (138), and utilizes dynamic
greenness maps derived from the NDVI index from the MODIS data (108, 114). In Australia,
MODIS-derived NDVI is also used for locust forecasting (26), although Weiss (146) questions its
predictive capacity. However, predicting locust presence can be improved if the remote sensing
information on areas of green vegetation and favored habitats is coupled with historical survey
data (26, 70, 111). An attempt has recently been made to include soil moisture information from
remote sensing (at 1-km resolution) in the tools available to desert locust managers, using SMOS
(Soil Moisture and Ocean Salinity) and MODIS sensors (31).
For the Asian migratory locust, satellite imagery is used to map the spatiotemporal distribution
of its preferred vegetation, the common reed (Phragmites australis) in central Asia (106, 112, 125–
127). Improved mapping of the reed habitats results in a more targeted locust survey and risk
assessment (70, 93). In China, satellite images have been used for habitat monitoring and post-
outbreak damage assessment of vegetation (61, 94, 137). In Madagascar, Franc et al. (42) used
SPOT satellite information to identify three new migration pathways of the red locust resulting
from deforestation between 1986 and 2004. These pathways provided access to new oviposition
zones, allowing the locust to breed and gregarize (71). Tronin et al. (140) estimated risk of the
Italian locust outbreak potential in Eurasia using Landsat information. In their detailed history
of remote sensing in locust monitoring and management, Latchininsky & Sivanpillai (73) and
Latchininsky (69) concluded that while satellite imagery has become a routine operational tool
for the desert locust and the Australian plague locust (18, 26), the technique has been seldomly
used for other locusts.
Advances in computer modeling mean that management of many species involves using GISs or
decision support systems (28, 85, 98, 117). These systems incorporate models that integrate data on
vegetation and weather conditions with locust development factors as a further aid in determining
when and where surveys should be conducted for nymphs and adults as well as provide guidance
on the best control strategy to use. An example of such a GIS-based system is used by the FAO:
RAMSES (Reconnaissance and Monitoring System of the Environment of Schistocerca) allows
national locust information services to manage, query, display, analyze, and map field and other
data (18). All field data from locust surveys, reports, and treatment programs are georeferenced
using a global positioning system (GPS), downloaded onto a laptop computer, and transmitted
by satellite and Internet to FAO headquarters in real time. The data are stored in databases at
national and international levels for analysis and distribution to all desert locust regions (16, 17,
19, 20). Similar systems are in operation in Australia (28) and China (84, 153). In the western
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Ultra-low volume
(ULV) spraying:
spraying of less than
5 L/hectare; ULV
equipment produces
very small droplets,
which ensures even
coverage with low
Barrier treatment:
application of a
moderately persistent
pesticide in strips some
distance apart, taking
advantage of the fact
that locust bands
Reduced agent and
area treatment
(RAAT): pest
management strategy
in which treated
swaths are alternated
with untreated swaths
naturally occurring
substances that control
pests and include
microbial insecticides
derived from
(viruses, bacteria,
fungi, protozoa, or
United States, CARMA (, an advisory system for managing grasshopper
infestations, has been successfully used since 1996 (50). These systems allow data to be analyzed
in real time, allowing forecasts to be made, alerts given, and extra resources made available where
and when required as a basis for more effective preventive control programs.
Most locust and grasshopper management programs still rely on chemical pesticides. While water-
based sprays are sometimes used because such equipment is what is available locally, vehicle-
mounted or aerial ultra-low volume (ULV) spraying is now becoming the primary method of
application of both chemical and microbial pesticides. ULV spraying has the advantage of allowing
more exact control of the droplet spectrum so that there is less waste from very large or very small
droplets, and the common application rate of one liter per hectare ensures sufficient droplets
are applied for adequate coverage. Suggested products, pros and cons, and doses are available in
the report of the FAO Pesticide Referee Group (39). In addition to overall blanket sprays, some
insecticides are considered efficacious as barrier treatments for control of hopper bands of locusts.
Barrier treatments were commonly used against the desert locust, and currently, bands of the
Australian plague locust are treated with chemical pesticide applied in barriers 300 to 500 m apart
by aircraft flying into the wind: Marching locust bands pass through the treated barriers, picking
up a lethal dose (3). In the United States, insect growth regulators are applied to grasshopper
infestations by a reduced agent and area treatment (RAAT) in which either all-terrain vehicles
or aircraft treat 5- to 30-m-wide swaths alternating with similar untreated swaths (87, 89). In
2010, this technique was used to treat >2 million ha of western US rangelands (101). Both barrier
treatments and RAATs aim to provide untreated areas (refugia), contributing to increased survival
of nontarget organisms, including parasites and predators.
Chemical pesticides have many side effects, and these have been increasingly elucidated, in-
cluding their impact on human health, the environment, nontarget organisms, and biodiversity
(32, 38, 51, 88, 110, 113, 119, 121, 130, 142). Furthermore, greater margins of safety for environ-
mentally sensitive areas are being provided by applying differential GPS guidance and recording
by aircraft of exact areas treated.
In recent years, there has been increased use of cultural and biological methods. For centuries,
migratory locust plagues were a regular occurrence in China, with locusts breeding in the large
flood-prone areas near rivers and lakes, but flood mitigation and environmental modification has
reduced the size of the areas favorable for breeding (156). Concerted control efforts within the
reduced favorable areas means that migratory locusts no longer reach plague proportions in China.
However, similar attempts at ecological control in outbreak areas of the red locust in Africa have
not been successful because of their costs and side effects (5).
A most remarkable recent advance has been the use of biopesticides as important components
of management programs (91). The naturally occurring fungus Metarhizium acridum was tested in
field trials against the desert locust (66) and Australian plague locust (59) during the 1990s, with
the first operational use against the latter species in the year 2000 (54). In recent years, there has
been a dramatic increase in the use of both M. acridum and the microsporidian Paranosema locustae
(formerly Nosema locustae), against both locusts and grasshoppers in China, with over 100,000 ha per
year sprayed with these products. A high level of mortality, though over a longer time period than
with chemicals, can be obtained both with Metarhizium (151, 152) and with Paranosema (45, 154).
This high mortality, combined with a price only slightly more than chemical pesticides because of
local production, means that nonchemical control forms an increasingly important part of locust
and grasshopper management in China. Metarhizium acridum has also been used operationally Locust and Grasshopper Management 23
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Decline: period
characterized by
breeding failure
and/or successful
control leading to the
dissociation of
swarming populations
and the onset of
against the migratory locust in East Timor, against red locusts in floodplains of East Africa and
against Schistocerca piceifrons in Mexico. A number of other countries have tested biopesticides
but still use only chemicals operationally. Even so, the advantages of using biopesticides, which
include specificity to locusts and grasshoppers and preservation of natural enemies (152), mean
that the credibility of having biopesticides as part of management programs is increasingly being
recognized (55).
6.1. The Importance of Sustainability
Locust and grasshopper management is essential for food security and is part of ensuring that
agriculture is economically viable. While ecological conditions largely determine the origin of
outbreaks and most are now managed by preventive strategies, the sustainability of locust and
grasshopper management systems can be seriously constrained by social, financial, economic, and
organizational factors (90). A significant constraint is the reduction in resources during recessions.
There is generally sufficient funding for management of species where outbreaks are common,
since funding organizations usually recognize that outbreaks sometimes increase in size and so have
mechanisms for providing moderate increases in resources when needed. However, for species that
have long periods between major outbreaks and plagues, funds are often abundant after an invasion
so that research develops and control facilities are strengthened. But after a number of years of
minimal locust activity, there tends to be a shift of resources to other, more immediate problems, so
that by the time the next outbreak begins, the means diminish and become largely ineffective (77,
78, 90). This problem is typified by the desert locust (7): Early control of outbreaks is hampered
by a lack of emergency/contingency funds, the remoteness and inaccessibility of many primary
breeding areas, and the lack of well-equipped and well-coordinated national/regional monitoring
and control to contain locusts before they spread. Such efforts require a rapid increase in funding
that is further hampered by a lack of well-coordinated appeals to donors who have little initial
enthusiasm to respond quickly while populations are still moderate and may decline naturally
without leading to a plague. The result is a vicious cycle that has been observed many times with
many species. The latest example is in Madagascar, where the management strategy against the
migratory locust has failed again and again despite repeated restructuring projects and significant
international assistance.
In fact, many of the problems are organizational and a new approach to locust issues has been
suggested (81) that includes studies not only on ecological mechanisms but also on potential
economic, social, cultural, and organizational impediments, including risk management systems
and stakeholder strategies. Risk management needs to be seen as being a complex system that
recognizes the importance of the various players and organizations involved to ensure that there
are proper financial and organizational arrangements for a sustainable preventive approach that
includes early intervention and efficient control (80).
6.2. Improving Risk Management and Better Comprehension
of a Complex System
Such an approach has been initiated, with the focus moving from mainly reactive to more proac-
tive and comprehensive disaster risk reduction and management systems (107). Locust control
is increasingly seen as the management of a natural hazard that requires not only scientific and
24 Zhang et al.
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EN64CH02_ZhangL ARI 24 November 2018 11:21
technical mechanisms to be in place but also sufficient funds for their implementation as soon as
outbreaks begin (107). In recent years, revisions to governance mechanisms for the desert locust
have included setting up reserve funds and an innovative financing system that can evolve accord-
ing to the dynamics of the locust population (24). Risk management plans have been developed
and are regularly tested in the form of field simulations to verify that the system will be operational
in the event of a crisis (36, 107).
The sociopolitical context as well as the role of the different antilocust players is also being
investigated using multi-agent modeling (44). The recent invasions of the desert locust in Africa
and migratory locust in Madagascar have shown that a key problem is the limited coordination
among those involved in locust control. For instance, there needs to be much improvement in the
relationship between local organizations/field teams and international donors so that funds can be
mobilized quickly and early intervention and emergency management effectively implemented.
Better communication is needed not only between scientists who have investigated improved
techniques/strategies and the field scouts and technicians needed for implementation but also
between rural communities and the pesticide companies from which they need to rapidly obtain
pesticides for control. These various players involved in managing locust outbreaks often have
very diverse and sometimes conflicting interests (80), making preventive management very much
a complex system. The operation of such a system is being improved by multi-agent modeling
that explores the interactions between the various stakeholders. Promising results have already
been obtained, as modeling has shown in a parsimonious way that a failure to remember the
importance of preventive management is sufficient to generate the observed cycles of invasions
(44). Furthermore, preventive management would be made more efficient if funding institutions
increased their base level of support to control units by just a few percent (44).
The constant and significant progress of locust and grasshopper management toward being green,
efficient, and precise can serve as a model for crop protection in general (Figure 2). However, the
increasing constraints on broad-acre chemical pesticide use mean that to ensure continuing success,
new methods must be discovered and implemented, and the effects of both chemical pesticides
and their biopesticide alternatives on nontarget organisms and ecological systems investigated.
Improvements are required in the rapid location and treatment of locusts and grasshoppers, and
unmanned aerial vehicles and drones could be most useful in this regard. While there has been
an improved understanding of locust behavior (21, 109, 122), the precise role of pheromones and
other semiochemicals needs to be clarified if they are to become useful tools in monitoring and
control (49). Functional genome sequencing could provide many molecular targets that might be
useful in control: The proteins involved in odor detection and chitin synthesis are possibilities
(120, 150). And while there are Metarhizium and Paranosema commercial biopesticides, obtaining
increased virulence and higher stress resistance by selection and genetic modification could aid in
increasing the use of these two biological control agents (144, 155). The potential of other natural
control agents, such as microorganisms (bacteria, viruses, nematodes), parasitic or predatory in-
sects, and plant extracts, needs to be evaluated in locust control. The efficacy of new and existing
products could be increased through new formulations such as those using nanocarriers (86). And
the various human-made effects that promote higher numbers of locusts and grasshoppers (12,
26) need to be better understood to avoid further increases in numbers as climate change takes
Locust and grasshopper outbreaks are often international in nature, and transboundary
movement is common, making increased regional cooperation between countries in management Locust and Grasshopper Management 25
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EN64CH02_ZhangL ARI 24 November 2018 11:21
Bendiocarb, chlorpyrifos,
diubenzuron, fenitrothion, pronil,
lambda-cyhalothrin, malathion,
Decision making
Monitoring and forecasting
High density Medium density
Precise application
Barrier treatment/
Chemical pesticides
Biological control
Nosema Metarhizium Biodiversity
Ecological control
GIS-, GPS- , RS-, IT-based information platform
Figure 2
Schematic diagram of the current preventive locust management system. Locust population density is
monitored and forecast using an information platform that is built with high technologies, such as
geographic information systems (GIS), global positioning systems (GPS), remote sensing (RS), and
information technology (IT)/computer science. With this platform, people make decisions for control
according to locust densities and location of infestations. Chemical control may be implemented when locust
density is high and may involve barrier treatments—in other words, spraying of pesticide in barriers
300–500 m apart by aircraft flying in rangeland or reduced agent and area treatments (RAATs). When locust
density is medium or in environmentally sensitive areas, a recommendation is made to implement biological
control, such as Metarhizium (fungal microbial control agent) or Nosema (protozoan microbial control
agent), or with ecological methods, such as an increase of biodiversity in the locust habitat. The information
platform leads to well-timed control action, precisely applied using GPS navigation.
programs essential. Robust mechanisms need to be put in place to ensure continuous financial
support at national and international levels so that treatment programs can be put in place in a
timely manner as part of successful strategies of sustainable preventive management.
1. The widespread nature of many locust and grasshopper infestations means that most
countries recognize that their effective management requires government intervention
and, at times, international cooperation.
2. Benefits and costs of locust and grasshopper control are increasingly better understood,
and the recognition of the damage they can cause has led to an increasing paradigm shift
from crop protection to preventive management.
3. Preventive strategies are increasingly implemented as being the most rational, effective,
and economically feasible methods of control. As a result, outbreaks are now better
controlled and often shorter in duration and reduced in extent.
26 Zhang et al.
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EN64CH02_ZhangL ARI 24 November 2018 11:21
4. Preventive management strategies rely on major recent advances in locust and grasshop-
per biology and ecology, as well as on a reasonably good understanding of the critical
factors leading to population increases.
5. There is now a better recognition that surveys for isolated locusts are important in
recognizing the first steps in population increases leading to outbreaks.
6. Locust and grasshopper management rely on more efficient monitoring and control
techniques, an increasing use of biological products, and high-level technologies such as
satellite imagery and geographic information systems.
7. The constant and significant progress of locust and grasshopper control toward being
green, efficient, and precise can serve as a model for crop protection in general.
1. Population dynamics during recession periods must be better understood.
2. The various human-made effects promoting outbreaks of locusts and grasshoppers need
to be better understood to avoid further increases in numbers as climate change takes
3. New methods must be discovered and implemented to forecast and monitor the rapid
location of gregarious locust infestations.
4. New formulations will be useful in increasing the efficacy of new and existing products,
including those using nanocarriers.
5. Improved use of biological control agents can be achieved by increasing the range of
agents available and improving their virulence by selection and genetic modification.
6. New control molecular targets will be needed; the study on functional genes could provide
many molecular targets that might be useful in control.
7. The role of locust pheromones and other semiochemicals for potential use in monitoring
and control should be clarified.
8. The sustainability of locust and grasshopper control must be better assured by considering
not only scientific and technical aspects, but also socioeconomic mechanisms involved in
the management of these pests.
The authors are not aware of any affiliations, memberships, funding, or financial holdings that
might be perceived as affecting the objectivity of this review.
The work by L.Z. was supported by the foundation from the Chinese Ministry of Agriculture
(2014-Z18) and that of A.L. by a USDA NIFA Crop Protection and Pest Management Extension
Implementation grant to the University of Wyoming. Locust and Grasshopper Management 27
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Annual Review of
Volume 64, 2019 Contents
An Unlikely Beginning: A Fortunate Life
Elizabeth A. Bernays ppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppp1
Locust and Grasshopper Management
Long Zhang, Michel Lecoq, Alexandre Latchininsky, and David Hunter ppppppppppppppppp15
The Ecology of Collective Behavior in Ants
Deborah M. Gordon ppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppp35
Invasion Success and Management Strategies for Social Vespula Wasps
Philip J. Lester and Jacqueline R. Beggs ppppppppppppppppppppppppppppppppppppppppppppppppppppp51
Invasive Cereal Aphids of North America: Ecology and Pest Management
Michael J. Brewer, Frank B. Peairs, and Norman C. Elliott ppppppppppppppppppppppppppppppp73
Blueberry IPM: Past Successes and Future Challenges
Cesar Rodriguez-Saona, Charles Vincent, and Rufus Isaacs pppppppppppppppppppppppppppppppp95
Development of Baits for Population Management of Subterranean
Nan-Yao Su pppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppp115
Biology and Control of the Khapra Beetle, Trogoderma granarium,a
Major Quarantine Threat to Global Food Security
Christos G. Athanassiou, Thomas W. Phillips, and Waqas Wakil ppppppppppppppppppppppp131
Vectors of Babesiosis
Jeremy S. Gray, Agust´ın Estrada-Pe ˜na, and Annetta Zintl pppppppppppppppppppppppppppppp149
Movement and Demography of At-Risk Butterflies: Building Blocks for
Cheryl B. Schultz, Nick M. Haddad, Erica H. Henry, and Elizabeth E. Crone ppppppppp167
Epigenetics in Insects: Genome Regulation and the Generation of
Phenotypic Diversity
Karl M. Glastad, Brendan G. Hunt, and Michael A.D. Goodisman ppppppppppppppppppppp185
Bee Viruses: Ecology, Pathogenicity, and Impacts
Christina M. Grozinger and Michelle L. Flenniken pppppppppppppppppppppppppppppppppppppp205
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Molecular Evolution of the Major Arthropod Chemoreceptor Gene
Hugh M. Robertson pppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppp227
Life and Death at the Voltage-Sensitive Sodium Channel: Evolution in
Response to Insecticide Use
Jeffrey G. Scott pppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppp243
Nonreproductive Effects of Insect Parasitoids on Their Hosts
Paul K. Abram, Jacques Brodeur, Alberto Urbaneja, and Alejandro Tena pppppppppppppp259
Movement Ecology of Pest Helicoverpa: Implications for Ongoing Spread
Christopher M. Jones, Hazel Parry, Wee Tek Tay, Don R. Reynolds,
and Jason W. Chapman pppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppp277
Molecular Mechanisms of Wing Polymorphism in Insects
Chuan-Xi Zhang, Jennifer A. Brisson, and Hai-Jun Xu ppppppppppppppppppppppppppppppppp297
Fat Body Biology in the Last Decade
Sheng Li, Xiaoqiang Yu, and Qili Feng ppppppppppppppppppppppppppppppppppppppppppppppppppp315
Systematics, Phylogeny, and Evolution of Braconid Wasps: 30 Years of
Xue-xin Chen and Cornelis van Achterberg ppppppppppppppppppppppppppppppppppppppppppppppp335
Water Beetles as Models in Ecology and Evolution
David T. Bilton, Ignacio Ribera, and Andrew Edward Z. Short ppppppppppppppppppppppppp359
Phylogeography of Ticks (Acari: Ixodida)
Lorenza Beati and Hans Klompen pppppppppppppppppppppppppppppppppppppppppppppppppppppppppp379
Cumulative Index of Contributing Authors, Volumes 55–64 ppppppppppppppppppppppppppp399
Cumulative Index of Article Titles, Volumes 55–64 ppppppppppppppppppppppppppppppppppppp404
An online log of corrections to Annual Review of Entomology articles may be found at
Contents ix
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... The migratory Locusta migratoria is considered one of the world's most harmful insect pests, whose swarms can devastate vast areas of crop and pasture. 1,2 This insect appears in two developmental phases-solitary and gregarious-that differ in morphological, physiological, and behavioral traits, with only the gregarious phase forming swarms that threaten agricultural production. 2,3 Numerous behavioral and ecological laboratory and field studies have tried to decipher the phase shift from solitary to gregarious animals and, by doing so, targeted the formation of locust swarms and their biological control. ...
... 1,2 This insect appears in two developmental phases-solitary and gregarious-that differ in morphological, physiological, and behavioral traits, with only the gregarious phase forming swarms that threaten agricultural production. 2,3 Numerous behavioral and ecological laboratory and field studies have tried to decipher the phase shift from solitary to gregarious animals and, by doing so, targeted the formation of locust swarms and their biological control. [4][5][6] Phase shift seems to be governed by population density, which, in turn, is affected by external factors such as weather and food abundance. ...
Full-text available
Article Odorant detection in a locust exhibits unusually low redundancy Highlights d The migratory locust emits sex-, phase-, and developmental-stage-related odorants d The response to odorants depends on sex, phase, and stage of the behaving animal d To detect these odorants, locusts use narrowly tuned odorant receptors
... Locust and grasshopper outbreaks are highly problematic for agriculture (Brader et al., 2006;Latchininsky, 2013;Millist 2011;Wright, 1986;Zhang & Hunter, 2017), although satellite-based locust monitoring technologies (Cressman, 2013;Latchininsky, 2013;Latchininsky et al., 2016;Propastin, 2013), modern forecast methods (Krall et al. 1997), and modern locust control (Lecoq, 2001;Zhang et al., 2019;Zhang & Hunter, 2017) are available in many countries suffering from this ancient plague. Effective locust control is still challenging and involves researchers (Lecoq & Cease, 2022a), companies, local locust control organizations, and governments, of which some receive support from the Food and Agriculture Organization (FAO) belonging to the United Nations Organization (UNO). ...
... Additionally, some chemical pesticides may also affect human health, including workers who are responsible for spray treatment on the ground. Alternative locust control agents have been available for many years, and the most popular ones are either based on the fungus Metarhizium sp. or the microsporidian Paranosema locustae (Lecoq & Cease, 2022b;Lecoq, 2010;Lockwood et al. 2000;Zhang et al., 2019). Under optimal conditions, it takes about 8 to 11 days after M. anisopliae treatment to kill locusts (Long & Hunter, 2005). ...
Full-text available
Locust swarm control is still a main topic in agriculture and is often based on the extensive use of chemical agents that can be problematic for the environment and human health. Currently, only a few alternative control agents are available on the market, such as neem oil, the fungus Metarhizium sp., and the microsporidian Paranosema locustae . In this study, we improved the formulation of a botanical insecticide that is based on linseed oil and was found to be effective against the desert locust, Schistocerca gregaria. To make sure that linseed oil is most effective, we first tested several natural plant oils in a comparative laboratory study. Linseed oil performed best and resulted in 100% mortality within only 2 days after a single spray treatment. However, this linseed oil formulation contains three expensive essential oils, thus we further improved it to avoid costly essential oils. A much lower concentration of linseed oil was also found to be highly effective and killed adult S. gregaria within 3 days in an experiment performed under semifield conditions. Furthermore, a concentrated stock solution of this botanical insecticide was developed to increase stability and reduce shipping costs in areas where water for dilution is available. Mechanical treatment, applied during the preparation of this linseed oil emulsion, resulted in the formation of micro‐colloids, which prevent the separation of phases and enable 1:16 dilution with water containing bicarbonate. Interestingly, only 24 h after single spray treatment, locusts became immobile and most of them were unable to jump, which would make them easy prey for natural enemies. Later, insects died due to the hardening of the linseed oil emulsion. This novel linseed oil emulsion is harmless for humans, rather easy to produce, and remains stable over weeks in its concentrated form, which suggests that it is promising alternative agent for locust control.
... This study shows that locust invasion durations were determined by environmental factors and the stage of locust growth. In addition, the duration of locust invasions played a key role in vegetation consumption rates, risks, and reproduction rates, which ultimately affected the health of natural ecosystems and food production systems [35]. ...
... Consequently, the most widely used control measures proved to be more effective [38,39], and the control methods used in the early stages of development during the 2020 locust invasion included traditional methods involving the use of chemicals and pesticides applied through aerial and ground spraying. Whereas the results from the study show that these were very effective, the measures are associated with adverse environmental effects [35]. As such, there is a need to develop capacity for the near-future and future forecasting of desert invasions and plan for preventive management to minimise the use of spraying with chemicals, which becomes the only reliable measure if invasions are detected only after occurrence as a reactive control measure [38]. ...
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Desert locust invasions are still a danger to the well-being of natural and man-made ecosystems in the tropics. This study examined desert locust invasion duration, survival probability, and control as well as their effects on household food item consumption in the drylands of Uganda. Primary socioeconomic data were collected using various methods (household survey, focus group discussion, and key informant interviews) in May/June 2020 to document the perceptions of households regarding locusts. Our findings reveal that the most significant drivers of desert locust invasions were rainfall, surface temperature, strong winds, soil moisture, soil type, and vegetation type (p ≤ 0.05). The locusts lasted between 3 and 4 weeks. The survival probability of locusts beyond 1 week was 90%. There were significant differences in the day’s food items consumed before and after the locust invasion, except for ground nuts and cashew nuts (p ≤ 0.05). The number of days per month the food items were consumed decreased after the locust invasion. The most effective locust control measure undertaken was the use of ground and aerial pesticide spraying. The major sources of desert locust control information were radio and television. This information is a prerequisite in desert locust invasion preparedness, response, and recovery but can also strengthen sustainable green economy efforts, especially in fragile semi-arid ecosystems.
... Interactions between fire and herbivores drive plant and nutrient dynamics and affect ecosystem service delivery in open ecosystems. Grasshoppers are widely seen as pests in competition with economically-valuable livestock for herbaceous primary productivity (Zhang et al. 2019). Hewitt and Onsager (1983) estimated grasshoppers consume nearly USD400 million (USD1.7 billion, adjusted for inflation) worth of livestock forage per year in the western United States. ...
The capacity of a plant to maintain optimal cellular homeostasis under biotic and abiotic stressors is essential for plant growth and development. Desert ecosystems occupy almost 35% of the planet’s land area. As a result of climate change, more regions are anticipated to experience water scarcity. Owing to its fatal impact on plant growth, development, and reproduction, which foreshadows a food shortage and significant economic losses, water deficiency has emerged as a global hazard. Drought-tolerant plants known as xerophytes may thrive and flourish in these challenging conditions. All xerophytic plants have similar forms, structures, and shapes to survive in such a xerophytic environment, even though they are not closely related to taxa. Xerophytes and the various ways in which they adapt to arid environments are currently a topic of interest on a global scale. The unexpected scarcity of evolutionary transitions between drought-avoiding and halophytic succulence may be explained in this chapter. The morphological, anatomical, and physiological adaptations and survival strategies that allow xerophytes to grow and complete their life cycles in dry and semiarid environments are also covered in this chapter.
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Locust plagues inflict severe agricultural damage. Climate change-induced extreme events like rainfall and droughts have expanded locust habitats. These new areas, often beyond routine monitoring, could become potential high-risk locust areas (PHRLA). Quantitatively understanding the outbreak mechanism driving drought and flood dynamics is crucial for identifying PHRLA, but such studies are scarce. To address this gap, we conducted a case study on locust outbreaks in Xiashan Reservoir, the largest reservoir in Shandong Province, China, in 2017 and 2018. Using time series satellite imagery and meteorological products, we quantitatively analyzed how drought–flood dynamics and temperature affect locust habitats, reproduction, and aggregation. Employing an object-oriented random forest classifier, we generated locust habitat classification maps with 93.77% average overall accuracy and Kappa coefficient of 0.90. Combined with meteorological analysis, we found that three consecutive drought years from 2014 to 2016 reduced the water surface area by 75%, expanding suitable habitats (primarily reeds and weeds) to cover 60% of the reservoir. Warm winters and high temperatures during locust key growth periods, coupled with expanding suitable habitats, promoted multi-generational locust reproduction. However, substantial flooding events in 2017 and 2018, driven by plentiful rainfall during key growth periods, reduced suitable habitats by approximately 54% and 29%, respectively. This compression led to high locust density, causing the locust plague and high-density spots of locusts (HDSL). Our study elucidates locust plague outbreak mechanisms under dynamic drought and flood environments. Based on this, we propose an approach to identify PHRLA by monitoring changes in drought and flood patterns around water bodies and variations in suitable habitat size and distribution, as well as surrounding topography. These findings hold significant implications for enhancing locust monitoring and early warning capabilities, reducing pesticide usage, and ensuring food and ecological security and sustainable agriculture.
The ancient migratory pest “Desert Locust” is one of the natural disasters that the generation of twenty-first century is still grappling with. Locusts belong to the family Acrididae of grasshoppers, which includes most short-horned grasshoppers. Globally, more than 10,000 grasshopper species are dispersed throughout tropical, temperate grassland, and desert areas. Of these, locusts are a group of 18–21 species with the ability to swarm over long distances. Desert locust, Schistocerca gregaria (Forksal), is the most dominant species of these with about 10 subspecies distributed in Europe, Asia, Africa, and Australia. Taxonomically, the locust and grasshopper are indistinguishable. But primary dissimilarity is that whether grasshopper species under favorable environment conditions forms a swarm (gregarious) or not (solitary). Often considered to be the “most important and dangerous of all migratory pests” which is known to invade 60 countries of the world. Interestingly, the proportion of crops damaged by locusts around the world is less than 0.2% but due to its voracious feeding, rapid reproduction, and extensive flight range, it can deprive a farmer from his sustenance in a single morning. Therefore, due to theses inherent features, the locusts have left indelible imprints in thoughts, views, scientific literature, along with arts of several cultures. Desert locust has three developmental stages (eggs, hoppers, adults), and its life cycle usually takes 2–4 months depending on the weather and ecological conditions. Although, the desert locust has been found in the Horn of Africa, since biblical times yet its intense outbreak in the recent past (2019–2020) is being linked with anthropogenic climate change and the increased frequency of extreme weather events such as El Niño and La Niña. Other factors like poor governance and the political uncertainties of these countries also intensified the plague and placed particular pressure on the already devastated nations. Unfortunately, the last locust outbreak (2019–2020) was the largest seen in the past 25, 30, 50, and 70 years in Somalia and Ethiopia, Pakistan, Iran, and Kenya, respectively, which posed serious economic, social, and environmental challenges. Overall, it affected 20 million persons in six (Ethiopia, Kenya, Somalia, South Sudan, Uganda, Tanzania) of the eight East African countries and put them at risk of acute food insecurity. The World Bank estimated that East Africa and Yemen alone suffered damages totaling US$8.5 billion. All over the world, maximum control measures implemented over years depended upon the application of conventional insecticides which are generally neurotoxic for locust. However, on account of their hazardous effects, there is an urge to invest for alternate controlling techniques which are ecofriendly as well as sustainable, like microbial insecticides. Other environmentally safe tools include georeferencing, global positioning systems, insect growth regulators, botanicals, and semiochemical traps. However, most of these are at infancy stages or not readily available in market. Herein, this chapter a review about the historical aspects, biology, and physiology of desert locusts is being presented. Furthermore, this chapter also sheds light on how climate change played a role in the in the irruption of the locust crisis, repercussions of the locusts invasion, and the potential of novel tools like remote sensing and the fungal-based biopesticides in its management is discussed.
Microsporidia are obligate intracellular single-cell eukaryotic parasites that can infect almost all kinds of animals and cause microsporidiosis. However, there are a few achievements of microsporidiosis treatments. Nosema bombycis could cause a microsporidiosis condition, pébrine, in the silkworm. Treatment and prevention of pébrine are still the research hotspots in sericulture. In this study, N. bombycis was treated with K 2 CO 3 , the spore walls were removed by centrifugation, and then, the alkali-soluble germination proteins were used as antigens to develop monoclonal antibodies (mAbs). Three mAbs were successfully screened and one mAb named G9 showed the highest titer among these monoclonal antibodies after enzyme-linked-immunosorbent serologic assay (ELISA). Mass spectrometry analysis confirmed that the mAb G9 could recognize the N. bombycis spore wall protein 1. Furthermore, the heavy chain and light chain sequences of the G9 monoclonal antibody were cloned, respectively. The vectors that expressing the intact antibodies and the single-chain variable fragments (scFvs) of G9 were constructed, and then, these vectors were used to develop the transgenic silkworm cell lines or transgenic silkworms. The inhibitory effects against N. bombycis were evaluated by the count of microsporidia and qPCR. The scFvs showed better effect on blocking the proliferation of N. bombycis than the intact antibody, and the scFv without the secretory signal peptide was more effective than that with signal peptide. Our study has provided novel strategies for microsporidiosis control and the essential groundwork for the future development of N. bombycis- resistant transgenic silkworms. IMPORTANCE There are a few reports on the resistance of microsporidia, including Nosema bombycis . Here, the alkali-soluble germination proteins of N. bombycis were used as immunogens to prepare a monoclonal antibody, and its single-chain variable fragments effectively blocked microsporidia infection. Our study has provided novel strategies for microsporidiosis control and demonstrated a useful method for the potential treatment of other microsporidia diseases.
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Abstract This paper presents the first attempt to include soil moisture information from remote sensing in the tools available to desert locust managers. The soil moisture requirements were first assessed with the users. The main objectives of this paper are: i) to describe and validate the algorithms used to produce a soil moisture dataset at 1 km resolution relevant to desert locust management based on DisPATCh methodology applied to SMOS and ii) the development of an innovative approach to derive high-resolution (100 m) soil moisture products from Sentinel-1 in synergy with SMOS data. For the purpose of soil moisture validation, 4 soil moisture stations where installed in desert areas (one in each user country). The soil moisture 1 km product was thoroughly validated and its accuracy is amongst the best available soil moisture products. Current comparison with in-situ soil moisture stations shows good values of correlation (R>0.7R>0.7) and low RMSE (below 0.04 m3 m−3). The low number of acquisitions on wet dates has limited the development of the soil moisture 100 m product over the Users Areas. The Soil Moisture product at 1 km will be integrated into the national and global Desert Locust early warning systems in national locust centres and at DLIS-FAO, respectively. Keywords Remote sensing; Soil moisture; Desert locust management; West Africa; SMOS; Disaggregation; Sentinel-1
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Locusts and grasshoppers are major economic pests in China and are controlled by a strategy of preventive management where about 1.5 million ha are treated each year. The preventive management system aims to keep locusts and grasshoppers at lower densities, so that the dense swarms seen in the past are no longer common and crop and pasture damage minimized. There is substantial cultural control, including conservation of natural enemies and reducing the area of favorable habitats through habitat modification. Even with substantial cultural control, locust and grasshopper infestations are still widespread, with 127 field stations having more than 2000 technicians involved in monitoring and control. These officers monitor and treat locust and grasshopper infestations and the data collected are integrated into a national computer-based platform. These data are analyzed and news bulletins are issued on where and when the densest infestations are likely to be so that extra resources can be provided when needed as part of coordinating an effective locust and grasshopper management program. In the past, treatments were by chemical pesticides, but in recent years there has been an increasing use of bio pesticides: namely, the naturally occurring fungus Metarhizium acridum and the microsporidian Paranosema locustae. While such products were used in only 5% of treatments during 2004, their use has increased to over 30% in recent years, which amounts to over 100,000 ha per year sprayed. These applications of bio pesticides against locusts and grasshoppers are more than all of the rest of the world combined.
Acridids (grasshoppers and locusts) can range from being rare curiosities to abundant menaces. Some are threatened with extinction and become subjects of intensive conservation efforts, while others are devastating pests and become the objects of massive control programmes. Even within a species, there are times when the animal is so abundant that its crushed masses cause the wheels of trains to skid (the Rocky Mountain grasshopper, Melanoplus spretus Walsh in western North America in the 1860s and I 870s), while at other times the animal is alarmingly scarce (the Rocky Mountain grasshopper went extinct in the early 1900s). Why are there these extremes in one insect family, and even in a single species? The NATO workshop examined this paradox and its implications for Environmental Security, which must address both the elements of land use (agricultural production and pest management) and conservation of biodiversity. The reconciliation of these objectives clearly demands a critical assessment of current knowledge and policies, identification of future research, and close working relationships among scientists. Insects can present two clear faces, as well as the intervening gradation. These extremes require us to respond in two ways: conservation of scarce species and suppression of abundant (harmful) species. But perhaps most important, these opposite poles also provide the opportunity for an exchange of information and insight.
Preventive management of locust plagues works in some cases but still fails frequently. The role of funding institution awareness was suggested as a potential facilitating factor for cyclic locust plagues. We designed a multi-agent system to represent the events of locust plague development and a management system with three levels: funding institution, national control unit and field teams. A sensitivity analysis identified the limits and improvements of the management system. The model generated cyclic locust plagues through a decrease in funding institution awareness. The funding institution could improve its impact by increasing its support by just a few percent. The control unit should avoid hiring too many field teams when plagues bring in money, in order to assure that surveys can be maintained in times of recession. The more information the teams can acquire about the natural system, the more efficient they will be. We argue that anti-locust management should be considered as a complex adaptive system. This would not only allow managers to prove to funders the random aspect of their needs, it would also enable funders and decision-makers to understand and integrate their own decisions into the locust dynamics that still regularly affect human populations.
The desert locust is an agricultural pest that is able to switch from a harmless solitarious stage during recession periods, to swarms of gregarious individuals that disperse long distances and affect areas from western Africa to India during outbreak periods. Large outbreaks have been recorded through centuries, and the Food and Agriculture Organization keeps a long-term, large-scale monitoring survey database in the area. However, there is also a much less known subspecies that occupies a limited area in southern Africa. We used large-scale climatic and occurrence data of the solitarious phase of each subspecies during recession periods to understand whether both subspecies climatic niches differ from each other, what is the current potential geographical distribution of each subspecies, and how climate change is likely to shift their potential distribution with respect to current conditions. We evaluated whether subspecies are significantly specialized along available climate gradients by using null models of background climatic differences within and between southern and northern ranges, and applying niche similarity and niche equivalency tests. The results point to climatic niche conservatism between the two clades. We complemented this analysis with species distribution modeling to characterize current solitarious distributions and forecast potential recession range shifts under two extreme climate change scenarios at the 2050 and 2090 time horizon. Projections suggest that, at a global scale, the northern clade could contract its solitarious recession range, while the southern clade is likely to expand its recession range. However, local expansions were also predicted in the northern clade, in particular in southern and northern margins of the current geographical distribution. In conclusion, monitoring and management practices should remain in place in northern Africa, and in southern Africa the potential for the subspecies to pose a threat in the future should be investigated more closely. This article is protected by copyright. All rights reserved.
In the late eighties large-scale control operations were carried out to control a major desert locust upsurge in Africa. For the first time since the banning of organochlorine pesticides these operations relied mainly on non-persistent pesticides such as organophosphates and pyrethroids. The amount of pesticides sprayed and the area covered were probably the highest in the history of locust control and raised criticism with respect to efficacy, economic viability and environmental impact. As a consequence, applied research into the problem was intensified, both at the national and the international level, with the goal of finding new and environmentally sound approaches and solutions to locust and grasshopper control. Emphasis was laid on developing new control agents and techniques. Based on these research topics, this book offers - a concise yet comprehensive overview of current and new strategies in locust control with implications for general pest control, - an introduction to new control agents (e.g., mycopesticides, botanicals, semiochemicals and chemicals), - results of economic analyses of crop loss assessment and control operations, - findings from studies of the ecology of selected African locusts and grasshoppers, - results and priorities of environmental impact assessment in locust control. The book is dedicated to applied researchers and decision-makers in national and international agricultural institutions and organizations.
Locusts are grasshoppers that belong to the Acrididae family, of the Orthoptera order. They constitute one of the biggest threats to global food security. Their swarms can attack hundreds of species of plants and destroy most major crop varieties. Locusts are known to consume the equivalent of their own body weight in green vegetation daily. Besides the enormous distribution ranges, their voracity and polyphagy make locusts extremely dangerous pests. Outbreaks have occurred on every continent except Antarctica and affect 10% of the world’s population. Locusts have been the enemies of crops since the dawn of agriculture. They are mentioned in sacred books such as the Torah, the Koran and the Bible. Locust swarms have brought devastation and famine to entire nations. For example, in 1958 in Ethiopia, locusts destroyed 167,000 tonnes of grain, enough to feed 1 million people for a year. Locust plagues continue to be devastating in the 21st Century. In 2003–2005, 8 million people in more than 20 countries suffered from ravages caused by swarms of desert locusts, Schistocerca gregaria, with an estimated 80–100% of crops lost in afflicted regions, mostly in sub-Saharan Africa.
The desert locust, Schistocerca gregaria (Forskal) (Orthoptera: Acrididae), is a major pest and well known in its gregarious phase. However, it is not well understood during recession periods, when the solitarious phase populations are discrete. Nonetheless, these populations are at the origin of the invasions when ecological conditions become favourable. This lack of knowledge of the solitarious phase individuals impedes effective preventive management of this pest. Archive data collected in Algeria from 1980 to 2011 were used to analyse solitarious population dynamics across the Algerian Sahara where some outbreak areas are located that play a major role in the invasion process. The results confirm previous empirical observations on solitarious population dynamics. First, a clear difference could be documented between the northern and southern Saharan regions of Algeria concerning the locust dynamics and the impact of environmental conditions. The importance of runoff was clear to create suitable habitats over a long period and to very distant places from rainy areas. Second, a link, on an annual basis, between green vegetation and presence of solitarious locusts was found. Third, statistical relationships between various locations demonstrated a clear regional dynamics. Our study confirmed the importance of migrations of solitarious populations among Algerian regions and more generally within the recession area of this species. The operational implications of these findings are multiple. First, they confirm the need of a flexible and scalable preventive system during the year, from 1 year to another and with a clear distinction between the northern and southern Saharan areas of Algeria. Second, they also confirm the necessity for the inclusion of wadis and soil moisture estimations from remote sensing in geographic information systems for preventive management. And third, they clearly illustrate the importance to target solitarious locusts for more efficient preventive survey operations.
The Asian Migratory locust (Locusta migratoria migratoria L.) is a pest that continuously threatens crops in the Amudarya River delta near the Aral Sea in Uzbekistan, Central Asia. Its development coincides with the growing period of its main food plant, a tall reed grass (Phragmites australis), which represents the predominant vegetation in the delta and which cover vast areas of the former Aral Sea, which is desiccating since the 1960s. Current locust survey methods and control practices would tremendously benefit from accurate and timely spatially explicit information on the potential locust habitat distribution. To that aim, satellite observation from the MODIS Terra/Aqua satellites and in-situ observations were combined to monitor potential locust habitats according to their corresponding risk of infestations along the growing season. A Random Forest (RF) algorithm was applied for classifying time series of MODIS enhanced vegetation index (EVI) from 2003 to 2014 at an 8-day interval. Based on an independent ground truth data set, classification accuracies of reeds posing a medium or high risk of locust infestation exceeded 89% on average. For the 12-year period covered in this study, an average of 7504 km² (28% of the observed area) was flagged as potential locust habitat and 5% represents a permanent high risk of locust infestation. Results are instrumental for predicting potential locust outbreaks and developing well-targeted management plans. The method offers positive perspectives for locust management and treatment of infested sites because it is able to deliver risk maps in near real time, with an accuracy of 80% in April-May which coincides with both locust hatching and the first control surveys. Such maps could help in rapid decision-making regarding control interventions against the initial locust congregations, and thus the efficiency of survey teams and the chemical treatments could be increased, thus potentially reducing environmental pollution while avoiding areas where treatments are most likely to cause environmental degradation.