ArticlePDF Available

Constraints to Vegetable Production Resulting from Pest and Diseases Induced by Climate Change and Globalization: A Review



Vegetable production worldwide is constrained by pests and diseases which effects are exacerbated by climate change and variability. Greenhouse gas emissions are also increasing due to poor agricultural practices and other human activities. This will continue to have a negative impact on the prevalence of insect pests and diseases. This review focuses on the climatic factors that impact on insect pests and diseases of vegetable crops. High atmospheric temperatures and elevated carbon dioxide increases pest development, survival of pests and distribution of pest to new areas. The distribution of insect pests and diseases are not due to climate changes only but are also a result of globalisation and poor biosecurity measures at country borders. There is limited information on the distribution of pests and diseases due to globalisation in African countries. New exotic pests will continue to be introduced to countries if biosecurity measures are not improved. Future research must focus on how to manage emerging pests and diseases influenced by high temperatures and carbon dioxide and other climatic conditions which influence pest severity under smallholder farmers in the southern African regions.
Journal of Agricultural Science; Vol. 9, No. 10; 2017
ISSN 1916-9752 E-ISSN 1916-9760
Published by Canadian Center of Science and Education
Constraints to Vegetable Production Resulting from Pest and Diseases
Induced by Climate Change and Globalization: A Review
Mutondwa M. Phophi
& Paramu L. Mafongoya
Department of Crop Science, School of Agricultural, Earth and Environmental Sciences, University of
KwaZulu-Natal, Scottsville, Pietermaritzburg, South Africa
Correspondence: Department of Crop Science, School of Agricultural, Earth and Environmental Sciences,
University of KwaZulu-Natal, Private Bag X01, Scottsville, 3209, Pietermaritzburg, South Africa. E-mail:
Received: July 1, 2017 Accepted: August 9, 2017 Online Published: September 15, 2017
doi:10.5539/jas.v9n10p11 URL:
Vegetable production worldwide is constrained by pests and diseases which effects are exacerbated by climate
change and variability. Greenhouse gas emissions are also increasing due to poor agricultural practices and other
human activities. This will continue to have a negative impact on the prevalence of insect pests and diseases.
This review focuses on the climatic factors that impact on insect pests and diseases of vegetable crops. High
atmospheric temperatures and elevated carbon dioxide increases pest development, survival of pests and
distribution of pest to new areas. The distribution of insect pests and diseases are not due to climate changes only
but are also a result of globalisation and poor biosecurity measures at country borders. There is limited
information on the distribution of pests and diseases due to globalisation in African countries. New exotic pests
will continue to be introduced to countries if biosecurity measures are not improved. Future research must focus
on how to manage emerging pests and diseases influenced by high temperatures and carbon dioxide and other
climatic conditions which influence pest severity under smallholder farmers in the southern African regions.
Keywords: biosecurity, emerging pests, insect pest management, smallholder farmers
1. Introduction
More undernourished people are found in African regions and this has remained a great challenge in the
Sub-Saharan Africa (FAO, 2015). South Asia and Sub-Saharan Africa constitutes at least one billion of people
who suffer from malnutrition, lacking carbohydrates, vitamins, and other micro-nutrients (Keatinge et al., 2011).
Smallholder farmers do not only grow vegetables for income purposes but also for improvement of human
nutrition at household level. Vegetables are rich in essential micro-nutrients such as vitamin A, C, E, zinc, copper,
iron and antioxidants (Afari-Sefa et al., 2016). FAO (2004) recommends that a human being needs to consume
200 g of vegetables per day. However, vegetable consumption is still below 200 g per day especially for the poor
and this results in the rising rates of malnutrition (Keatinge et al., 2011).
The major common constraints to vegetable production in smallholder farmers are pests and diseases and these
limits farmers in obtaining better crop yield and ensuring food security. Some smallholder farmers have adopted
the use of chemicals to manage insect pests and diseases in vegetable production. However, there is a challenge
of insect resistance that is building up and this is becoming a constraint to insect pest management and obtaining
good crop yields (Jallow et al., 2017). The overuse of pesticides is also leading to health problems and impacting
the environment when not handled properly. Jallow et al. (2017) indicated that 65% of farmers agreed that the
use of chemicals for insect management is hazardous to the environment and 70.5% confirmed that pesticides
can be dangerous to human health. This will remain a huge problem to farmers who depend on chemicals to
manage insect pests, especially when climate change is having an impact on the biology and distribution of
insect pests.
2. Greenhouse Gas Emissions
The increase of greenhouse gas emissions resulting from human activities and other natural factors has become a
world-wide threat impacting the environment through climate change. These activities include the use of fuels Journal of Agricultural Science Vol. 9, No. 10; 2017
and deforestation and are contributing to the elevation of carbon dioxide and increase of temperatures
(Olabemiwo et al., 2017). Carbon dioxide contributes 58.8% greenhouse gasses (Olabemiwo et al., 2017).
Agricultural practices can also contribute to the emission of greenhouse gases when carbon dioxide is being
released. Carbon dioxide can be released through burning of plant materials and also through decomposition of
soil organic matter (Kang & Banga, 2013). These emissions of greenhouse gasses are expected to increase
because human population is increasing and it depends on agriculture for food (Kang & Banga, 2013). The use
of fertiliser in crops also contributes to greenhouse gas emissions. Nitrous oxide can be emitted through the use
of nitrogen fertilisers. Farmers can find other alternatives of fertilising their crops with less emissions of
greenhouse gasses.
3. Climate Variability
Extreme weather events such as heavy rainfalls leading to floods, severe droughts and extreme heat waves have
been increasing since the past decades and are still expected to increase in the next few decades to come (Mirza,
2011). These processes will continue to have implications on agricultural productivity on a global scale (Gornall
et al., 2010). Climate change is most likely to alter insect pests and the relationship between the host and insect
can be affected (Bale et al., 2002) thus resulting in negative impact on crop productivity. Some crops which are
known to be resistant to insect pest can become susceptible and react positively to pest damage under the
influence of climate change and global warming (Reddy, 2013).
Climate change and global warming can result in observable changes to insect pest life such as migration of
insect pest and invasion to other areas, increase in geographical range of insects, and influencing the population
of insect pests by increasing their rate of development and cycles within a short period of time (Reddy, 2013).
All these changes resulting from climate change can contribute to difficulty to predict the effect of pest
management and this can result in low crop yields. Also a one year change of climate can influence pest
outbreaks and if the pests are aggressive enough, there can be a regime shift of insect pests (Kiritani, 2013).
Insect pests that are most affected by climate change and global warming are those that are ectothermic because
they can quickly acclimatize to different environmental conditions. This gives them an advantage to multiply
aggressively, increasing their threat to crop production (Ferrer et al., 2014). Examples of insect pests that easily
adapt to high temperatures include, aphids, whitefly and stem borers (Sharma, 2014).
Increased temperatures and elevated atmospheric carbon dioxide are the most conspicuous factors of climate
change that have become a threat to crop production (Mendelsohn, 2008). These two factors have been
increasing and are still predicted to increase by the end of twenty-first century (Trebick et al., 2015). The two
factors have resulted in shifts of pests from lower latitudes to higher latitudes (Barzman et al., 2015) and also
altered insect pest pressures negatively through emerging pests and positively through migration, thus creating
consequences to the environment and to crop productivity (Ziska & McConnell, 2016).
4. Impact of Temperature on Insects and Disease
Global warming exerts extensive effects on insect life and the terrestrial ecosystem and it is still predicted to
cause major changes in the near future. Temperature increase has been predicted to elevate by 3.4
C by the end
of twenty-first century (Barzman et al., 2015). With all these predictions, vegetable production in dryland areas
will continue to be vulnerable to these temperature effects (Macfadyen et al., 2016). Policy makers can be able to
make use of these predictions to make suitable policies for farmers on management strategies of mitigation and
adaptation to pests impacting crop production (Sharma & Prabhakar, 2014). Global warming can affect insect
population in a number of ways such as: changes in population growth rate, the increase in number of insect
generations, the extension of geographical range, the introduction of species to alternative host plants, the
increase of invasion risk by migrating insects and also overwintering of insects (Bale et al., 2002; Maran &
Pelini, 2016).
High temperatures can alter the growth and development of insects affecting the fecundity and mortality of
insects (Khaliq et al., 2014). The increase in insect population numbers occurs when the growth and
developmental rate has been speed up. For example short living insects that have adapted to high temperatures
can be able to increase the number of generations in a year when influenced by warmer conditions (Van Dyck et
al., 2014). Meisner et al. (2014) showed that higher temperatures increased aphid (Aphidius ervi) growth and
developmental rate and also increased the span of adult life under 20
C and 27
C. This means that the higher
the developmental rate, the more the insect cycles and the higher the population size. This can result in more
severe damage to crops if farmers are failing to control insect pests. Journal of Agricultural Science Vol. 9, No. 10; 2017
Different stages in the life cycle of an insect can respond differently to high temperatures (Zhang et al., 2015).
Some insects can be highly favoured by high temperatures, influencing their population positively, whereas some
insects can result to high mortality rates under high temperatures. Diamondback moth (Putella xylostella) has
been monitored under high temperatures and it was reported that its growth and development was affected by
temperature. Egg production and the adult stage of this insect were decreased at higher temperatures. However,
the larval stage was found to be highly tolerant to high temperatures (Zhang et al., 2015). This means that there
could be implications when managing this insect pest under high temperatures in the near future. Aphidius ervi
found in peas was found to be tolerant when monitored in high temperatures. High temperatures influenced the
an increase in the developmental rates of this aphid and the adult stage was found to be more tolerant to high
temperatures thus resulting in increased rates of pea damage (Meisner et al., 2014).
Most insects have the potential for long distance mobility and flight. High temperatures can increase the mobility
of some insects as well as their distribution. Most insects usually move to the northern regions were they are able
to disappear from unsuitable climatic conditions (Ziska et al., 2013; Pulator et al., 2016). Most of these insects
that have high rates of migration are ectotherms and this type of insects is expected to continue shifting to higher
latitudes and altitudes in the next decades (Vanhanen et al., 2007). It has been predicted that insects will shift by
6.1 km to the upward poles per decade due to increased temperatures (Parmesan & Yohe, 2003). In the UK, the
lepidopteran moths and butterflies have been reported each year to have increased in migration rate and this has
been linked to increased temperatures in the south west Europe (Sparks et al., 2007). Grapholita molesta (Busck),
a lepidopterian moth has the potential to adapt to high temperature environment and has been found to have good
flying abilities under high temperature (Ferrer et al., 2014). In Africa, smallholder farmers are most likely to be
vulnerable to this factor because severe high temperatures are predicted to be experienced in African areas
(Biber-Freudenberger et al., 2016). Tuta absoluta, Ceratitis cosyra and Bactrocera invadens are the most
common insects pests found in Africa and they have been recorded to increase their suitability to different types
of environment across the African continent (Biber-Freudenberger et al., 2016). The advantage to habitat
suitability by insect pest can influence the increase of the ability to spread and acclimatize to different
environments while at the same time causing damage to crops.
High winter temperatures can affect and also influence the presence and outbreaks of insect pest (Reddy et al.,
2015). Warmer winters can result to reduction in mortality rates of insect pests and this often leads to high
infestations on crops thus increasing the damage and yield loss (Harrington et al., 2001). Warmer winters can
also increase the distribution of insect pests because of reduced mortality rates (Battisti et al., 2005). The African
bollworm (Herlicoverpa amigera) is regarded as one of the major insect pest in agricultural production. This
insect has the ability to overwinter due to increased temperatures in winter season (Reddy et al., 2015). The
southern green stink bug (Nezara viridula): heteroptra: pentatomidae) showed a high survival rate in winter
season due to increased warmer conditions (Musolin et al., 2009). It can be expected that due to high
temperatures, warmer seasons can be long and therefore resulting to warm winter conditions which can result to
high presence of insect pest.
Temperature, light and water are the main factors that control and influence the development of plant diseases,
their survival, the rate of multiplication and the rate at which inoculums disperse and penetrate on plants,
spreading the diseases on plants (Ahanger et al., 2013). Increased temperatures influence the growth and
development of most plant pathogens. Pathogens that depend on temperature for development can be active due
to high temperature, and if utilising the warmer conditions, they can develop and start spreading on crops if left
uncontrolled (Ahanger et al., 2013). Most plant pathogens that have a short life cycle may reproduce rapidly and
have a high distribution rate when exposed to higher temperatures (Coakley et al., 1999). When temperatures are
high, pathogens can migrate to new areas where there are potential susceptible hosts that can influence the
development of diseases (Etterson & Shaw, 2001). Plants that grow in the tropics are the ones that are usually
affected by diseases that are influenced by high temperatures. This is because these plants have got a narrow
temperature growth range and they are quick to respond positively to temperature changes (Ghini et al., 2011).
Late blight diseases have been recorded in the earlier ages to be aggressive at 10-25
C temperatures. However,
recently these diseases have now adapted to higher temperatures of up to 27
C (Luck et al., 2011). Due to
predictions of increasing temperatures in this century, pathogens are most likely to be found in large numbers
and resulting in difficulties in controlling them.
High temperatures can influence the development and spread of stem rust caused by Puccinia graminis f. sp
tritici (Gautam et al., 2013). Stem rust has been reported to be more aggressive when temperatures are high and
it has shown to be quick in adapting to high temperature changes (Mboup et al., 2012). Bacteria such as
Rasoltonia solanacearum was also reported that it grows and develops rapidly due to high temperatures. High Journal of Agricultural Science Vol. 9, No. 10; 2017
temperatures with low rainfall can also influence the spread of viruses such as Maize dwarf mosaic virus and
Beet yellow virus (Clover at al., 1999; Olson et al., 1990). The severity of these diseases will affect smallholder
farmers because of high vulnerability to climatic changes and also lack of knowledge to manage diseases.
5. Extreme Weather Events
Climate change can result in extreme weather events that can have an impact in agricultural production and
insect pests and diseases (Adamo et al., 2012). These extreme events include long periods of drought spells, long
spells of heavy rainfall and extreme high temperatures (Rosenzweig et al., 2001). The long spells of high
temperatures and drought are linked to El Nino scenarios (Rosenzweig et al., 2001). Long dry spells and drought
can enhance insect population growth rates and reproduction rates (Adamo et al., 2012). Pests found in the
temperate regions are predicted to be more affected by extreme weather events. They are predicted to increase in
population during long dry spells (Adamo et al., 2012). A study was done in South Africa on some of the
problematic fruit flies (Ceratitis capitata) commonly known as the medfly and C. rosa commonly known as the
Natal fruit fly. These fruit flies showed an increase in their abundance due to extreme high temperatures.
However their fecundity rates showed to decrease in low temperatures (Nyamukondiwa et al., 2013). The lower
temperatures in the Western Cape province of South Africa can have an influence in reducing the effectiveness of
these flies, therefore high rates of mortality and less damage to the fruits (Nyamukondiwa et al., 2013).
Heavy rainfalls affect insect biology and survival negatively. Most insects are vulnerable to heavy rainfall, thus
affecting their growth development and population (Pellegrino et al., 2013). Heavy rainfall can result to
increased mortality rates of insects (Pellegrino et al., 2013). A study was done and showed that heavy rainfalls
can result to high rates of locust mortality. Heavy rainfalls affected the locusts eggs and the nymph survival was
reduced severely (Woodman, 2015).
Extreme weather events can result to insect pest outbreaks (Ju et al., 2013). These outbreaks can wipe out crop
species due to severe damage and spread of diseases. They can also influence invasion of alien pest species that
may have an impact in crop yield (Kannan & James, 2009). However invasion of new species due to extreme
events will also depend on whether the insect is adapting well to the new environment and climatic conditions
(Sharma, 2014).
Frequent heavy rainfall can influence the spread of pathogens and fungal diseases. Many plant pathogens are
known to respond positively when there is rainfall (Thompson et al., 2013). Plant pathogens such as
Phytophthora cinnamomi and Botryosphaeria doithidea are amongst the many pathogens that are known to
respond positively when there is rainfall (Thompson et al., 2013).
6. Impact of Elevated Carbon Dioxide on Insects and Diseases
Presently, the level of atmospheric carbon dioxide is 400 µmol
and it is predicted to potentially increase by the
end of 21
century to 650 µmol
(Trebecki et al., 2015; Vassiliadis et al., 2016). Most studies have been done on
the impact of carbon dioxide
on crop plants but little is known about atmospheric carbon dioxide on plant insect
pests and diseases. Carbon dioxide can affect plant growth and development by altering the physiology and
morphology of the plant. Such alterations induced by carbon dioxide can affect the diet quality and feeding
behaviour of insects (Ryan et al., 2014). Although these alterations affect the feeding behaviour of insects, these
insects are affected differently. Elevated carbon dioxide was found to have an impact in the lepidopteran
Herlicoverpa amigera. The feeding behaviour of the larvae was affected by elevated carbon dioxide. Results
showed that elevated carbon dioxide contributed to the increase of food consumption and metabolism of the
larvae and this gives an indication that Helicoverpa amigera larvae may cause more damage under elevated
carbon dioxide (Akbar et al., 2016). Herlicoverpa amigera is one of the major global insect pest that feed on
brassicas and its damage can lead to high yield loss (Machekano et al., 2017). The ability of this insect pest to
cause damage can be highly influenced by climatic changes (Machekano et al., 2017). Sucking insects such as
aphids can also be affected by elevated carbon dioxide (Newman, 2003). Some studies show an increase in aphid
population due to elevated carbon dioxide (Newman, 2003). However, some plants can produce defensive
compounds which can affect the feeding, development and survival of sucking insect pests (War et al., 2012).
Elevated concentrations of carbon dioxide are most likely to affect the pressure of insect pest in both managed
and unmanaged crops. These pressures from insect pests can either be in a form migration to new areas or they
can be in a form of new introduction in areas (Ziska et al., 2016), and these often underlies their distribution and
abundance, hence the level of damage they cause to crops (Mazzi & Dion, 2012). Elevated concentrations of
carbon dioxide also affect insect pest growth and their development and this often results in changes in the
interaction between insect pests and their crop host (Akbar et al., 2016; Elad & Pertot, 2014). Journal of Agricultural Science Vol. 9, No. 10; 2017
Carbon dioxide also has an impact on plant diseases. Carbon dioxide influences the growth and development of
the crops, crop canopy and the microclimate as well as the quantity of tissues susceptible to diseases (Pannga et
al., 2013). The canopy microclimate can influence the presence, survival and dispersal of plant pathogens
(Pannga et al., 2013).
Elevated carbon dioxide may result in extreme changes of reproduction, spread and severity of plant diseases and
this is a threat to food security (Gautam et al., 2013). Plant diseases can result from bacteria, fungi and viruses
and their interaction with plants can be highly influenced by weather patterns including elevated carbon dioxide
(Nopsa et al., 2014). A range of foliar diseases can be encouraged by dense canopies due to increased carbon
dioxide. Such foliar diseases that are influenced by elevated carbon dioxide include powdery mildew, rust, leaf
spots and also blights and these diseases are known to develop in warm weather conditions (Gautum et al., 2013).
Diseases such as late blight (Phytopthora infestans) known to infect potatoes, blast (Pyricularia oryzae) and
sheath blight (Rhizoctonia solani) known to infect rice are known to cause significant damage to these crops,
hence more threat under elevated carbon dioxide (Gautam et al., 2013).
7. Impact of Globalisation on Spread of Insect Pests and Diseases
Alien species can impact crop production in countries and this can lead to economic crop yield loss (Saccaggi et
al., 2016). Alien species are defined as species that have the ability to live and adapt outside their natural habitat
(Sujay et al., 2010). Alien species can occur in the form of insect pests, fungal diseases, viruses and other species
that are also non-agricultural (Sujay et al., 2010). Most of these alien pests have the ability to outcompete native
pests because they can highly adapt to new environments. They have aggressive growth and reproduction and
they can move long distances at the same time spreading and causing damage to agricultural crops (Rejmanek &
Richardson, 2000). The risk of these alien pests have been increasing and has become a great threat to
agricultural production, especially insect pests such as arthropods due to their small size and high ability to
tolerate different climatic conditions (Saccaggi et al., 2016).
Alien pest species can be introduced to the country intentionally or unintentionally. Alien pests can be introduced
by movement of people and goods from one country to the other, through imports of agricultural products such
as fruits, vegetables, seeds (Hulme et al., 2008) and propagation materials (Saccaggi et al., 2026). Improvement
of logistic has recently resulted in the ease of commodities to be exported to different countries globally, this has
been found to influence the introduction of alien pests through contamination (Hulme, 2009). The increase of
transport networks, both aquatic and terrestrial, is also playing a role in the introduction of pests to other
countries (Hulme, 2009). The magnitude and the level of distribution of these alien pests on agricultural products
between countries is still not well understood (Paini et al., 2016). However, it is said that the most countries to
suffer from invasions by alien species are the sub-Saharan countries and also those countries that receive large
volumes of agricultural imports (Paini et al., 2016).
8. Phytosanitary Measures
Biosecurity measures are taken to reduce the introduction of alien pest species in countries (Cope et al., 2016).
Biosecurity includes phytosanitary measures which are conducted at the country borders. Detection of alien
species are conducted whereby travellers, machines, luggage and food are inspected for hidden pests (Liebhold
et al., 2006). Other methods of detection include vacuuming travellers’ goods to remove small or unseen
particles such as seeds and insects, preventing their entry into foreign countries (Fortune, 2006). Small insect
pests are not easy to detect at the border when biosecurity measures are taken (Saccaggi et al., 2016). This
becomes a problem when small insect pests with high reproductive rates pass through the border and adapt to the
foreign environment. These pests then result to high damage to crop production. Some alien pests are able to
enter foreign countries due to poor biosecurity measures (Caley et al., 2015). Insect pests that belong to order
coleoptera, hemiptera, lepidoptera and diptera have been entering Australia during the years of 1986-2005. These
pests have been recorded all these years because the biosecurity measures has been poorly facilitated, therefore
increasing high rates of invasion and damage from these pests (Caley et al., 2015). To develop effective
biosecurity measures, policy makers need to understand the sources of these alien pests and diseases and their
rate of distribution and how they adapt to different environmental conditions and also the damage they can cause
of agricultural products (Bourdot et al., 2012). As indicated previously, most alien pests are introduced as
contaminants, there will be an increase of challenges to policy makers and the management of these pests. There
is a need to monitor the trends in which alien species are being introduced in foreign countries and the
biosecurity measures should be regulated more effectively to reduce the entry of alien pest (Hulme et al., 2008). Journal of Agricultural Science Vol. 9, No. 10; 2017
9. The Role of Vegetables in Human Nutrition
The amount and types of nutrients consumed by human beings daily can affect the human’s nutritional status.
The lack of good nutrition in human diet may result in serious health conditions which can affect the lifestyle of
humans in future (Keatinge et al., 2011). Malnutrition conditions are very common in young children especially
those in the sub-Saharan African countries (Brown & Pollitt, 1996). Lack of nutrition in children can affect the
development of brains (Brown & Pollitt, 1996). However this damage can be reversed if proper nutrients are
consumed (Brown & Pollitt, 1996). A diet with high fat and sugar result in poor development and reduction of IQ
in children (Northstone et al., 2011). High consumption of foods with protein, vitamins can result in better
chances of increasing the children’s IQ (Northstone et al., 2011). Nutrition is also very important for pregnant
women and for women who are in the reproductive era. Foods that contain vitamins, minerals and folate are
highly essential for preventing foetal damage in pregnant women (FAO/WHO, 2004). There is nutrition
transition in the west African countries such as Ghana and Senegal (Bosu, 2015). There is high consumption of
sugar and fatty foods leading to increasing rates of obesity by 115% since 2004 in the west African countries
with less consumption of vegetables and fruits (Bosu, 2015). Studies have shown that there is increased rate of
hypertension in Burkina Faso and Cape Verde due to lack of good nutrition consumption (Busu, 2015). Lack of
vitamin has been reported in 250,000 to 500,000 African children, resulting to blindness every year and half of
the kids dying within 12 months of their blindness (WHO, 2013). Iron is another essential nutrient that has been
reported to be deficient in the sub-Saharan countries, resulting to health consequences (WHO, 2002). There are
still 2 billion people who are undernourished in African countries and this has increased malnutrition problems
because food demand is higher than the food supplied (FAO, 2013). The nutrition transition in African countries
does not only affect human beings in higher socioeconomic strata, but it also affects the poor and the uneducated
who are already affected by poor sanitation and other diseases (Busu, 2015).
Vegetable consumption is the first important step to overcome human malnutrition, especially to those who are
more vulnerable to lack of nutrients (Yang & Keding, 2009). Vegetables are very important for reducing
malnutrition problems in human beings (Ojiewo et al., 2015). Most vegetables which contain essential nutrients
include cabbages, tomatoes, black nightshade, cowpea and soybeans. These vegetables contain nutrients such as
vitamin A, vitamin E, protein, iron, folate, zinc and calcium which are very essential for human diet (FAO/WHO,
2004). Vegetables can be made available to households when grown in home gardens. There is need to increase
vegetable production for human beings to obtain essential micronutrients through their diets (Ojiewo et al., 2015).
The green revolution concentrated on staple crops such as maize, wheat, rice and cassava to eliminate poverty in
the African regions. However, these crops do not contain essential micro-nutrients (Ojiewo et al., 2015).
Tenkouano (2011) suggested that these crops rather constitute to “grain revolution” than “green revolution” due
to lack of micro-nutrients. Vegetables and legumes contains essential micro-nutrients and needs to be part of a
well-balanced diet and has to be included as part of the green revolution (Tenkouano, 2011).
10. Traditional Vegetables
Traditional vegetables can also be consumed to combat malnutrition problems. These types of vegetables are not
usually grown and supplied on a large scale (Mampholo et al., 2016). However, they can be grown and sold
locally with less management and can tolerate adverse weather conditions. Most of these vegetables are redroot
pigweed (Amaranthus retroflexus), mustard spinach and black nightshade (Solanum nigrum) and are most
consumed in South Africa (Mampholo et al., 2016). Traditional vegetables are rich in calcium, zinc, vitamin A, B,
E, and other antioxidant compounds (Yang et al., 2009). Absence of these nutrients in the human diet can result
to what is called “hidden hunger” and other chronic diseases (Yang & Keding, 2009). Black nightshade contains
compounds such as flavonoids, ascorbic acid, protein, vitamins and other minerals such as calcium, potassium
and phosphorus (Van Averbeke et al., 2007). Consumption of these vegetables can help to alleviate poverty and
food insecurity in rural households (Van Averrbeke et al., 2007). Solanum nigrum also contains high levels of
zinc and magnesium (Uusiku et al., 2010). All these vegetables are very common in the Limpopo Province and
continuous provision of these vegetables can help reduce malnutrition in households, at the same time reducing
food insecurity and making income when sold to markets. However, the constraints in growing these vegetables
include lack of quality seeds, varieties, shortage of water, pests and disease infestation and also lack of
information on markets (TsChirlea et al., 2004).
11. Major Insect Pests of Vegetables Grown in South Africa
Most of these insect pests that causes damage to vegetables include bagrada bug (Bagrada hilaris), diamondback
moth (Putella xylostella), and aphids. Journal of Agricultural Science Vol. 9, No. 10; 2017
Bagrada bug (Bagrada hilaris) commonly known as painted bug is a native pest in most countries including
African countries. This bug is known to have originated in Asia (Halbert & Eger, 2010). Bagrada bug commonly
feeds on crucifer’s crops and brassica crops such as cabbages, mustard, kale and other brassica crops (Bundy et
al., 2012). It has also been reported to feed on crops of other families such as Zea mays L., Sorhgum bicolor (L.)
sunflower (Helianthus annuus) and cotton (Gossypium hirsutum) in the United States (Reed et al., 2011).
Bagrada bug is considered as one of the major serious pests resulting to huge threats in vegetable production
(Huang et al., 2014). It has been reported for the first time in Los Angeles County, Carlifornia and Anzona in
2008 (Palumbo & Natwick, 2010). This bug has been found to have increased its distribution to native countries
including African countries. It has been reported in countries such as Zimbabwe (Grzywackz et al., 2010),
Botwsana (Obopile et al., 2008), South Africa, Mozambique, Kenya and Tanzania (Infonet-Biovision, 2015).
However little is known about the host preferences of bagrada bug (Huang et al., 2014) and there is little
understanding of bagrada bug distribution and damage in South Africa.
Bagrada bug is a sucking insect with piercing mouthparts. Bagrada bug takes 41 days to complete its entire life
cycle in conducive environments of warmer climate (Reed et al., 2013). After eclosion, female bugs become
receptive to the male bug in 1-2 days and it takes 4-5 days for oviposition to occur after mating for the first time
(Singh & Malik, 1993). This pests can lay 100-200 eggs underside of the leaves, stem or on loose soil. However,
this pest does not lay eggs in large numbers like other insect pests, it lays eggs singly or in groups of 10 eggs
(Reed et al., 2013). It can overwinter in soil cracks to escape cold weather conditions which are not good for its
survival (Reed et al., 2013).
This insect is usually triggered by high temperatures for effective activity. High temperatures influences the
walking and mating of bagrada bug (Huang et al., 2013). A study was done in feeding of bagrada bug and results
suggested that this pest feeds effectively on brassica crops in the afternoon and evening when temperatures are
high (Huang et al., 2013).
Bagrada bug can be found feeding from crop seedling to maturity stage (Divya et al., 2015; Patel et al., 2017).
Studies have shown that bagrada bug can invade in newly emerging crops and causing damage to the apical
meristem of the crops (Palumbo & Natwick, 2010; Huang et al., 2014). This bug uses a lacerate and flush
feeding method (Hori, 2000). During feeding on crops, bagrada bug secrete saliva enzymes which results in crop
damage (Reed et al., 2013). Bagrada bug also removes cell sap from the plant tissues of brassica and
non-brassica crops, resulting in crop deterioration (Banuelos et al., 2013). Excessive feeding on apical meristem
of vegetables can result in poor head/crown formation in cabbages and this becomes a consequence of poor
marketable cabbages (Palumbo & Natwick, 2010). It may also result to death of growing plant tip and
deformation of adventitious budding (Reed et al., 2013). Damage caused by bagrada bug can lead to death of
plants (Huang et al., 2014). Adult or mature crops can result to malformation of leaves and circular scorching of
leaves due to damage caused by bagrada bug (Reed et al., 2013). However young susceptible crops normally
show signs of wilting and death of tissues leading to death of the plant (Reed et al., 2013). Leaves of young
susceptible crops can show white spots as a result of feeding by bagrada bug (Patel et al., 2017).
Diamondback moth is also one of the major global insect pests than can result to huge crop loss. It is commonly
known to feed on brassica crops such as cabbages (Machekano et al., 2017). Diamondback moth is said to be
ubiquitous and it can survive throughout the whole year, feeding and resulting to crop damage (Furlong et al.,
2013). This insect pest has certain factors that give it the ability to cause severe damage to crops if left
uncontrolled. It has high potential of reproduction, ability to distribute and migrate to other areas, it has the
ability to adapt easily to different environmental conditions, and it has high ability to reproduce throughout the
whole year remaining abundant and difficult to manage (Canico et al., 2013; Furlong et al., 2013). Diamondback
moth has been reported in African countries such as Kenya, South Africa, Malawi, Mozambique, Zambia,
Namibia, Zimbabwe and Botswana (APR, 2015). Brassica export to African countries is still in great demand
although there is high incidence of Diamondback moth. South Africa is one of the countries that has great
exportation of brassicas to neighbouring countries such as Mozambique, Angola, Lesotho and Swaziland (DAFF,
2015). However this pest has been found to be a constraint in the quality of brassica crops in South Africa, and
therefore this results to poor marketable products (Furlong et al., 2013). Southern African countries will continue
to be vulnerable to climate change (IPCC, 2014), and this will be problematic to brassica production because
diamondback moth is exacerbated by climatic changes and variability (Furlong et al., 2013). In countries such as
China, diamondback moth has costed the Chinese economy about US$0.77 billion annually (Li et al., 2016). Journal of Agricultural Science Vol. 9, No. 10; 2017
12. Farmers’ Control Methods
Most farmers use chemical method to manage diamondback moth. Research suggests that most small scale
farmers in Southern African countries rely on insecticides to manage DBM. Countries such as Mozambique has
100% reliance on chemical control (Camico et al., 2013) and Botswana has 98% reliance on chemical control for
this pest (Obopile et al., 2008), while Zambia and Namibia has about 70% reliance of chemical control
(Nyirenda et al., 2011). These farmers have been found to apply insecticides at different rates and at different
frequencies (Canico et al., 2013). Research has shown that most farmers in these Africa countries are applying
insecticides once every three weeks to control diamondback moth. However, due to high population of this pest,
farmers end up applying insecticides three times a week (Obopile et al., 2008). Such application results in insect
resistance development especially if chemicals of the same mode of action are applied, therefore also causing
implications in management of this pest. This type of application can also result to environmental contamination.
Some farmers are applying a mixture of different chemical ingredients to control diamondback moth. However it
has been recorded that most of these farmers are doing this without any guidance from the manufacturer and
therefore it becomes harmful to the environment (Ngowi et al., 2007). Diamondback moth has also been reported
to be resistance to many insecticides in China (Li et al., 2016). Integrated Pest Management has been proved to
be effective in reducing diamondback moth in China. China country has made more efforts to support
implementation of Integrated Pest Management and this has been adopted by many farmers. However, these
practices need to be supported continuously to prevent more insecticide reliance by farmers (Li et al., 2016).
According to the reviewed, there is little information reported on these pests in South Africa. There is a need to
address the impact of climatic changes especially high temperatures on the survival and population of emerging
pest in smallholder farmers. Most research has been conducted in commercial farmers and little is known with
regards to smallholder farmers and their management of these pests.
13. The Use of Companion Crops for Insect Pest Management
The use of companion crops is one of the ecological practices for smallholder farmers who don’t have resources
to manage insect pests that are damaging their main crops (Calumpang & Navasero, 2013). The main purpose of
growing companion crops is to protect main crops from insect pests that will cause damage and therefore
resulting in high yield loss. Companion crops can be grown as trap crops or intercrops and this can be referred to
as the push-pull strategy. Companion crops grown as intercrops attracts insect pests, making insect pests less
attractive to main crops and this is known as the “Push” (Cook et al., 2007). Companion crops grown as trap
crops ensures that insect pests that may feed on main crops are reduced in numbers. This is referred to as the
“Pull” (Cook et al., 2007). Companion crops grown as trap crops are usually grown around field crops (Khan et
al., 2001). Napier grass (Pennisetum purpureum Schumach) is one of the companion crops grown around maize
crop field. This grass can attract maize stem borer while reducing chances of attacking maize crops (Khan et al.,
Companion crops grown as intercrops can be used as repellents for insect pests (Finch & Collier, 2011). The idea
of these repellents is to release volatile chemical compounds that can deter insect pests. Insect pests are able to
detect repellent companion crops from a distance away from the plant and this can cause the pest to stay away
from the crop thus reducing damage to the main crops (Finch & Collier, 2011). Some of the crops that can be
grown to repel insect pest are eggplant (Solanum melongena L.), lemon grass (Cymbopogon citratus Stapf) and
marigold (Tagetes erecta L.) (Calumpang & Navasero, 2013). A study was conducted to repel corn borer using
eggplant and lemon grass as repellents. Results showed that the growth rate and damage caused by corn borer
was reduced. Companion crops can be artificial. These artificial crops are meant to disrupt the visual pest
processes and to interfere with the host selection process by the pest (George et al., 2013). Maize can be
intercropped with desmodium (Desmodium uncinatum Jacq DC) as a companion crop to repel stem borer moths
in maize crops. It can repel stem borer moths and it also has the ability to attract natural enemies of this insect
pest (Khan et al., 2014).
Companion crops can be grown for more than one purpose at the same time. It can be grown to repel insect pests
and also to improve soil fertility. For example desmodium spp crop can repel insect pests of maize at the same
time it can be used to improve soil fertility through biological nitrogen fixation and organic matter improvement
(Khan et al., 2014).
It is always a challenge to decide on which companion crops can be effective to manage insect pest. It is of
importance for farmers to know different companion crops which are effective before planting them. Companion
crops should be tolerant to drought if crop production is to be practiced in arid and semi-arid areas. These crops Journal of Agricultural Science Vol. 9, No. 10; 2017
should also be resilient to moisture stress since erratic rainfall and unpredictable rainfall patterns are expected
due to climatic changes (Khan et al., 2014).
There are few studies done on companion crops for pest management, most of them have focused on field crops
such as maize, sorghum and millet. Very few studies have looked on companion crops for vegetable pest
management. There is very limited knowledge of herbs used as companion crops for management of insect pests
on vegetable production. More studies have done trap crops to attract insect pest. Very little is known about
herbs that can be used to repel insect pests of vegetables through the odour they produce. There are few studies
conducted in South Africa under smallholder farmers that produce vegetables on companion crops. Therefore
there is a need for smallholder farmers who cannot afford insecticides to make use of this practice to manage
pests and to reduce insecticide application on their vegetable crops. This will also help to suppress the rate of
chemical resistance influenced by frequent insecticide application.
14. Areas of New Research
Most studies were conducted in temperate countries. Very few studies have been done in Africa. High
temperature in South Africa must be evaluated on its effects on new and emerging pests. Modelling techniques
must be used to predict the spread of new and emerging pests in South African provinces. More studies should
also be done on farmer’s perceptions on new and emerging pests and how it interacts with climate change and
variability. Studies must be done on invasive species entering southern African countries and South Africa
through globalisation, trade, plants, and plant products. Regional, national and global networks should work on
new and emerging pests for efficient use of resources in addressing this 21
century challenge.
15. Conclusion
This review has concluded that anthropogenic activities and some agricultural practices such as pesticide
application and burning of fuels do influence greenhouse emissions resulting to climatic changes. Climate
change and variability such as increased temperatures and levels of carbon dioxide can result in changes in the
biology of an insect. This can increase mortality rates, fecundity rates, growth and development of insects and
adaptation and distribution of insects to new areas. However this depends on the type of insects and the
conditions which are conducive for development. It is concluded that insect pests such as diamondback moth,
bagrada bug and aphids will continue to adapt well in warmer conditions and their distribution rate towards the
North Pole will be high due to the fact that they respond very well to high temperatures. It is expected that these
pests will result to extreme crop damage in warmer areas if they are left uncontrolled due to increased
generations and populations. It can also be expected that these pests may have high overwintering rates if
temperatures continue to be high. More research has been conducted on climate change and its effect on crop
yield. More research should focus on how ectothermic pests and other emerging pests should be managed when
influenced by climatic changes.
The distribution of insect pests and diseases does not only result from climatic changes. Globalisation also plays
a huge role in distributing native pests to countries. This review showed that the South African countries are
expected to be more vulnerable to introduction of new pests and diseases due to poor biosecurity measures.
Research should focus on long term monitoring of insect pest and diseases. New efficient strategies should
therefore be introduced at the borders to limit the introduction of native pests to countries. More research has
focused on the European countries. However, little is known on the introduction of new pests and diseases in the
Southern African countries. This gives an indication that government should provide funding for better
biosecurity measures.
The study is supported by National Research Foundation through the South African Research Chair: Agronomy
and Rural Development at the University of KwaZulu-Natal, in South Africa.
Adamo, S. A., Baker, J. L., Lovett, M. M. E., & Wilson, G. (2012). Climate change and temperate zone insects:
The tyranny of thermodynamics meets the world of limited resources. Environmental Entomology, 41,
Afari-Sefa, V., Rajendran, S., Kessy, R. F., Karanja, D. K., Musebe, R., Samali, S., & Makaranga, M. (2016).
Impact of nutritional perceptions of traditional African vegetables on farm household production decisions:
A case study of smallholders in Tanzania. Experimental Agriculture, 52, 300-313.
S0014479715000101 Journal of Agricultural Science Vol. 9, No. 10; 2017
Ahanger, R. A., Bhat, H. A., Bhat, T. A., Ganie, S. A., Lone, A. A., Wani, I. A., … Bhat, T. A. (2013). Impact of
climate change on plant diseases. International Journal of Modern Plant and Animal Sciences, 1, 105-115
Akbar, S. M., Pavani, T., Nagaraja, T., & Sharma, H. C. (2016). Influence of co
and temperature on metabolism
and development of Herlicoverpa amigera (Noctuidae: Lepidoptera). Environmental Entomology, 45,
Arthropod Pesticide Resistance Database (IRAC). (2015). Michigan State University. Retrieved from
Bale, J. S., Masters, G. J., Hodkinson, I. D., Awmack, C., Bezemer, T. M., Brown, V. K., … Whittaker, J. H.
(2002). Herbivory in global climate change research: Direct effects of rising temperature on insect
herbivores. Global Change, 8, 1-16.
Banuelos, G. S., Dhillon, K. S., & Banga, S. S. (2013). Oilseed brassicas in biofuel Crops. In B. P Singh (Ed.),
Production Physiology and Genetics (pp. 339-368).
Barzman, M., Lamichhane, J. R., Booij, K., Boonekamp, P., Desneux, N., Huber, L., … Messean, A. (2015).
Research and priorities in the face of climate change and rapidly evolving pest. Sustainable Agriculture
Reviews, 17, 1-27.
Biber-Freudenberger, L., Ziemacki, J., Tonnang, H. Z., & Borgemeister, C. (2016). Future risks of pest species
under changing climatic conditions. PLoS ONE, 11(4), e0153237.
Bourdot, G. W., Lamoureaux, S. L., Watt, M. S., & Kriticos, D. J. (2012). The potential global distribution of the
invasive weed Nasella neesiana under current and future climates. Biological Invasions, 14, 1545-1556.
Brown, J. L., & Pollitt, E. (1996). Malnutrition, poverty and intellectual development. Scientific American,
247, 38-43.
Bosu, W. K. (2015). An overview of the nutrition transition in West Africa: Implications for
non-communicable diseases. Proceedings of the Nutrition Society, 74, 466-477.
Bundy, C. S., Grasswitz, T. R., & Sutherland, C. (2012). First report of the invasive stink bug Bagrada hilaris
(Burmeister) (Heteropter: Pentatomidae) from New Mexico, with notes on its biology. Society of
Southwestern Entomologists, 37, 411-414.
Caley, P., Ingram, R., & DeBarro, P. (2015). Entry of exotic insects into Australia: Does border interception
count match incursion risk? Biological Invasions, 17, 1087-1094.
Calumpang, S. M. F., & Navasero, M. V. (2013). Behavioural response of the Asian corn borer Ostrinia
furnacalis Guenee (Lepidoptera: Pyralidae) and the earwig Euborelia annulipes Lucas (Dermaptera:
Anisolabiidae) to selected crops and weeds associated with sweet corn. Philippine Agricultural Scientist, 96,
Canico, A., Santos, L., & Massing, R. (2013). Development and adult longevity of diamondback moth and its
parasitoids Cotesia plutellae and Diadegma semiclausum in uncontrolled conditions. African Crop
Science Conference Proceedings, 11, 257-262.
Clover, G. R. G., Smith, H. G., Azam-Ali, S. N., & Jaggard, K. W. (1999). The effects of drought on sugar
beet growth in isolation and in combination with beet yellow virus infection. Journal of Agricultural
Science, 133, 251-161.
Coakley, S. M., Scherm, S., & Chakraborty, S. (1999). Climate change and disease management. Annual
Review of Phytopathology, 37, 399-426.
Cook, S. M., Khan, Z. R., & Pickett, J. A. (2007). The use of push-pull strategies in integrated pest
management. Annual Review of Entomology, 52, 375-400.
Cope, R. C., Ross, J. V., Wittmann, T. A., Prowse, T. A. A., & Cassey, P. (2016). Integrative analyses of the
physical transport network in Australia. PLoS ONE, 11, 0148831.
0148831 Journal of Agricultural Science Vol. 9, No. 10; 2017
DAFF. (2015). A profile of the South African cabbage market value chain: Department of Agriculture, Forestry
and Fisheries. Acardia, South Africa.
Elad, Y., & Pertot, I. (2014). Climate change impacts on plant pathogens and plant diseases. Journal of Crop
Improvement, 28, 99-139.
FAO. (2004). FAO S TAT . Food and Agriculture Organisation, Rome, Italy. Retrieved from
FAO. (2013). The state of food insecurity in the world 2013. The multiple dimensions of food security. Rome,
Italy. Retrieved from
FAO. (2015). The state of food insecurity in the world 2014. Rome: Food and Agriculture Organisation of the
United Nations. Retrieved from
FAO/WHO. (2004). Vitamin and mineral requirements in human nutrition. Food and Agricultural Organisation,
Rome. Retrieved from
Ferrer, A., Mazzi, D., & Dorn, S. (2014). Stay cool, travel far: Cold-acclimated oriental fruit moth females have
enhanced flight performance but lay fewer eggs. Entomologia Experimentils et Applicata, 151, 11-18.
Finch, S., & Collier, R. H. (2011). The inuence of host and non-host companion plants on the behaviour of pest
insects in eld crops. Entomologia Experimentalis et Applicata, 142, 87-96.
Fortune, A. L. (2006). Biosecurity at the extreme: Pathways and vectors between New Zealand and Scott Base,
Antarctica (M.Sc. thesis, University of Canterbury, Canterbury, NZ). Retrieved from
Furlong, M. J., Wright, D. J., & Dosdall, L. M. (2013). Diamondback moth ecology and management:
Problems, progress and prospects. Annals Review of Entomology, 58, 517-554.
Gautam, H. R., Bhardwaj, M. L., & Kumar, R. (2013). Climate change and its impact on plant diseases. Current
Science, 105, 1685-1691.
George, D. R., Collier, R. H., & Whitehouse, D. M. (2013). Can imitation companion planting interfere with host
selection by Brassica pest insects? Agricultural and Forest Entomology, 15, 106-109.
Ghini, R., Bettiol, W., & Hamada, E. (2011). Disease in tropical and plantation crops as affected by climate
changes: Current knowledge and perspectives. Plant Pathology, 6, 122-132.
Gornall, J., Betts, R., Burke, E., Clark, R., Camp, J, Willett, K., & Wiltshire, A. (2010). Implications of climate
change for agricultural productivity in the early twenty-first century. Philosophical Transactions of The
Royal Society B, 365, 2973-2989.
Grzywacz, D., Rossbach, A., Rauf, A., Russell, D. A., Srinivasan, R., & Shelton, A. M. (2010). Current control
methods for diamondback moth and other Brassica insect pests and the prospects for improved
management with lepidopteran-resistant Bt vegetable brassicas in Asia and Africa. Crop Protection, 29,
Halbert, S. E., & Eger, J. E. (2010). Bagrada bug (Bagrada hilaris) (Hemiptera: Pentatomidiae) an exotic pest
of the cruciferae established in the Western USA.
Harrington, R., Fleming, R. A., & Woiwod, I. P. (2001). Climate change impacts on insect management and
conservation in temperate regions: Can they be predicted? Agricultural and Forestry Entomology, 3,
Hori, K. (2000). Possible causes of disease symptoms resulting from the feeding of phytophagous Heteroptera.
In C. W. Schaeter & A. R. Panizzi (Eds.), Heteroptera of Economic Importance (pp. 10-35). CRC Press.
Huang, T.-I., Reed, D. A., Perring, T. M., & Palumbo, J. C. (2013). Diel activity and behaviour of Bagrada
hilaris (Hemiptera; pentatomidae) on dessert cole crops. Horticultural Entomology, 106, 1726-1738. Journal of Agricultural Science Vol. 9, No. 10; 2017
Huang, T.-I., Reed, D. A., Perring, T. M., & Palumbo, J. C. (2014). Host selection behaviour of Bagrada hilaris
(Hemiptera: pentatomidae) on commercial cruciferous host plants. Crop Protection, 59, 7-13.
Hulme, P. E., Bacher, S., Kenis, M., Klotz, S., Kühn, I., Minchin, D., … Vilà, M. (2008). Grasping at the
routes of biological invasions: A framework for integrating pathways into policy. Journal of Applied
Ecology, 45, 403-414.
Hulme, P. E. (2009). Trade, transport and trouble: Managing invasive species pathways in an era of
globalization. Journal of Applied Ecology, 46, 10-18.
Infonet-Biovision. (2015). Bagrada bug. Zurich. Retrieved from
Intergovernmental Panel on Climate Change (IPCC). (2014). Climate Change 2014: Synthesis Report. Fifth
Assessment Report (AR5), Contribution of Working Groups I, II and III to the Fifth Assessment Report
of the Intergovernmental Panel on Climate Change. IPCC: Geneva, Switzerland.
Jallow, M. F. A., Awadh, D. G., Albaho, M. S., Devi, V. Y., & Thomas, B. M. (2017). Pesticide risk behaviours
and factors influencing pesticide use among farmers in Kuwait. Science of the Total Environment, 574,
Ju, H., Vander Velde, M., Lin, E., Xiong, W., & Li, Y. (2013). The impacts of climate change on agricultural
production systems in China. Climate Change, 120, 313-324.
Kang, M. S., & Bang, S. S. (2013). Global agriculture and climate change. Journal of Crop Improvement, 27,
Kannan, R., & James, D. A. (2009). Effects of climate change on global diversity: A review of key literature.
Tropical Ecology, 50, 31-39
Keatinge, J. D. H., Yang, R. Y., Hughes, J., Easdown, W. J., & Holmer, R. (2011). The importance of vegetables
in ensuring both food and nutritional security in attainment of the millennium development goals. Food
Security, 3, 491-501.
Khaliq, A., Javed, M., Sohali, M., & Sagheer, M. (2014). Environmental effects of insects and their
population dynamics. Journal of Entomology and Zoology, 2, 1-17.
Khan, Z. R., Pickett, J. A., Wadhams, L., & Muyekho, F. (2001). Habitat management strategies for the control
of cereal stemborers and striga in maize in Kenya. International Journal of Tropical Insect Science, 21,
Kiritani, K. (2013). Different effects of climate change on the population dynamics of insects. Applied
Entomology and Zoology, 48, 97-104.
Li, Z., Zalucki, M. P., Yonow, T., Kriticos, D. J., Bao, H., Chen, H., … Furlong, M. J. (2016). Population
dynamics and management of diamondback moth (Plutella xylostela) in China: The relative contributions
of climate, natural enemies and cropping patterns. Bulletin of Entomological Research, 106, 197-214.
Liebhold, A. M., Work, T. T., McCullough, D. G., & Cavey, J. F. (2006). Airline baggage as a pathway for
alien insect species invading the United States. American Entomology, 52, 48-54.
Luck, J., Spackman, M., Freeman, A., Trebicki, P., Griffiths, W., Finlay, K., & Chakraborty, S. (2011). Climate
change and diseases of food crops. Plant Pathology, 60, 113-121.
Macfadyen, S., Mcdonald, G., & Hill, M. P. (2016). From species distribution to climate change adaptation:
knowledge gaps in managing invertebrate pests in broad-acre grain crops. Agriculture, Ecosystems &
Environment (In Press).
Machekano, H., Mvumi, B. M., & Nyamukondiwa, C. (2017). Diamondback moth, Plutella xylostella (L.) in
southern Africa: Research trends, challenges and insights on sustainable management options. Sustainability,
9, 1-23. Journal of Agricultural Science Vol. 9, No. 10; 2017
Mampholo, B. M., Sivakumar, D., & Thompson, A. K. (2016). Maintaining overall quality of fresh traditional
leafy vegetables of Southern Africa during the postharvest chain. Food Reviews International, 32, 400-416.
Maran, A. M., & Pelini, S. L. (2016). Insect communities. Climate Change (2nd ed., pp. 153-166). Elsevier B.V.
Mazzi, D., & Dion, S. (2012). Movement of insect pests in agricultural landscapes. Annals of Applied Biology,
160, 97-113.
Mboup, M., Bahri, B., Leconte, M., De Vallavieille-Pope, C., Kaltz, O., & Enjalbert, J. (2012). Genetic structure
and local adaptation of European wheat yellow rust populations: The role of temperature adaptation.
Evolutionary Applications, 5, 341-352.
Meisner, M. H., Harman, J. P., & Ives, A. R. (2014). Temperature effects on long-term population dynamics in a
parasitoid-host system. Ecological Monographs, 84, 457-476.
Mendelsohn, R. (2008). The impact of climate change on agriculture in developing countries. Journal of Natural
Resource Policy Research, 1, 5-19.
Mirza, M. M. Q. (2011). Climate change and extreme weather events: Can developing countries adapt? Climate
Policy, 3, 233-248.
Musolin, D. L., Tougou, D., & Fujisaki, K. (2009). Too hot to handle? Phenological and life history responses to
simulated climate change of the southern green stink bug Nezara viridula (Heteroptera: pentatomidae).
Global Change Biology, 16, 73-87.
Newman, J. A. (2003). Climate change and cereal aphids: The relative effects of increasing CO
and temperature
on aphid population dynamics. Global Change Biology, 10, 5-15.
Ngowi, A. V., Maeda, D. W., & Partanen, T. J. (2007). Knowledge, Attitudes and Practices (KAP) among
agricultural extension workers concerning the reduction of the adverse impact in agricultural areas in
Tan zan ia. Crop Protection, 26, 1617-1624.
Northstone, K., Joinson, C., Emmett, P., Ness, A., & Paus, T. (2011). Are dietary patterns in childhood
associated with IQ at 8 years of age? A population-based cohort study. Epidemiology and Community
Health, 66, 624-628.
Nyamukndiwa, C., Weldon, C. W., Chown, S. L., leRoux, P. C., & Tereblanche, J. S. (2013). Thermal biology,
population fluctuations and implications of temperature extremes for the management of two globally
significant insect pests. Journal of Insect Physiology, 59, 1199-1211.
Nyirenda, S. P., Sileshi, G. W., Belmain, S. R., Kamanula, J. F., Mvumi, B. M., Sola, P., … Stevenson, P. C.
(2011). Farmers’ ethno-ecological knowledge of vegetable pests and pesticidal plant use in Northern
Malawi and Eastern Zambia. African Journal of Agricultural Research, 6, 1525-1537.
Nopsa, J. F. H., Thomas-Sharma, S., & Garrett, K. A. (2014). Climate change and plant disease. Encyclopedia of
Agriculture and Food Systems, 2, 232-243.
Olabemiwo, F. A., Danmaliki, G. I., Oyehan, T. A., & Tawabini, B. S. (2017). Forecasting CO
emissions in the
Persian Gulf States. Global Journal of Environmental Science Management, 3, 1-10.
Obopile, M., Munthali, D. C., & Matilo, B. (2008). Farmers’ knowledge, perceptions and management of
vegetable pests and diseases in Botswana. Crop Protection, 27, 1220-1224.
Ojiewo, C., Keatinge, D. J. D. H., Hughes, J., Tenkouano, A., Nair, R., Varshney, R., … Silim, S. (2015). The
Role of Vegetables and Legumes in Assuring Food, Nutrition, and Income Security for Vulnerable Groups
in Sub-Saharan Africa. World Medical & Health Policy, 7, 3.
Olson, A. J., Pataky, J. K., D’Arcy, C. J., & Ford, R. E. (1990). Effects of drought stress and infection by Maize
dwarf mosaic virus in sweet corn. Plant Disease, 74, 147-151. Journal of Agricultural Science Vol. 9, No. 10; 2017
Palumbo, J. C., & Natwick, E. T. (2010). The bagrada bug (Hemiptera: Pentatomidae): A new invasive pest of
cole crops in Arizonia and Carlifonia. Plant Health Progress.
Paini, D. R., Sheppard, A. W., Cook, D. C., DeBarro, P. J., Worner, S. P., & Thomas, M. B. (2016). Global threat
to agriculture from invasive species. PNAS, 113, 7575-7579.
Parmesan, C., & Yohe, G. (2003). A globally coherent fingerprint of climate change impacts across natural
systems. Nature, 421, 37-42.
Patel, S., Yadar, S. K., & Singh, C. P. (2017). The incidence of painted bug, Bagrada hilaris (Burmeister) of
Brassica spp and Eruca sativa with respect to the date of sowing. Journal of Entomology and Zoology
Studies, 5, 774-776.
Pellegrino, A. C., penaflor, M. F. G. V., Nardi, C., Bezner-Kerr, W., Guglielmo, C. G., Bento, J. M. S., & McNeil,
J. N. (2013). Weather forecasting by insects: Modified sexual behaviour in response to atmospheric pressure
changes. PLoS ONE, 8, e75004.
Pannga, I. B., Hanan, J., & Chakraborty, S. (2013). Climate change impacts on plant canopy architecture:
Implications for pest and pathogen management. European Journal of Plant Pathology, 135, 596-610.
Pulatov, B., Hall, K., Anderson, M., & Jonsson, A. M. (2014). Effect of climate change on the potential spread of
the Colorado potato beetle in Scandinavia: An ensemble approach. Inter-Climate Research, 62, 15-24.
Reed, D. A., May, C., Lewis, T., & Perring, T. M. (2011). Effects of temperature and host plant on development,
fecundity and longetivity of the stink bug, Bagrada hilaris. Poster presented at the 59
annual meeting of
the Entomological Society of America, November 13-16, 2011.
Reed, D. A., Palumbo, J. C., Perring, T. M., & May, C. (2013). Bagrada hilaris (Hemiptera: Pentatomidae) an
invasive stink bug attacking Cole crops in the south-western united States. Journal of Integrated
Management, 4, 1-7.
Reddy, G. V., Shi, P., Hui, C., Cheng, X., Ouyang, F., & Ge, F. (2015). The seesaw effect of winter temperature
change on the recruitment of cotton bollworms Herlicoverpa amigera through mismatched phenology.
Ecology and Evolution, 5, 5652-5661.
Reddy, P. P. (2013). Impact of climate change on insect pests, pathogens and nematodes. Pest Management in
Horticultural Ecosystems, 19, 225-233.
Rosenzweig, C., Iglesias, A., Yang, X. B., Epstein, P. R., & Chivan, E. (2001). Climate change and extreme
weather events: Implications for food production, plant diseases and pests. Global Change & Human
Health, 2, 90-104.
Ryan, G. D., Emiljanowicz, L., Harri, S. A., & Newman, J. A. (2014). Aphid host-plant genotype × genotype
interactions under elevated co
Ecological Entomology, 39, 309-315.
Saccaggi, D. L., Karsten, M., Robertson, M. P., Kumschick, S., Somers, M. J., Wilson, J. R. U., & Terblance, J. S.
(2016). Methods and approaches for the management of arthropod border incursions. Biological Invasions,
18, 1057.
Sharma, H. C., & Prabhaka, C. S. (2014). Impact of climate change on pest management and food security.
Integrated pest Management (pp. 23-36). Academic Press, Elsevier, London, UK.
Sparks, T. H., Dennis, R. L. H., Croxtron, P. J., & Cade, M. (2007). Increased migration of Lepidoptera linked to
climate change. European Journal of Entomology, 104, 139-143.
Singh, H., Malik, V. S. (1993). Biology of painted bug (Bagrada cruciferarum). Indian Journal of Agricultural
Science, 63, 672-674.
Sujay, Y. H., Sacatagi, H. N., & Patil, R. K. (2010). Invasive alien insects and their impact on agroecosystem.
Karnataka Journal of Agricultural Sciences, 23, 26-34.
Rejmanek, M., & Richardson, D. M. (2000). What makes some conifers more invasive? Proceeding of the fourth
international conference (In Press).
Tenkouano, A. (2011). The Nutritional and Economic Potential of Vegetables. State of the World’s Food and
Agriculture 2011: Innovations that Nourish the Planet (pp. 27-38). New York: W. W. Norton & Company. Journal of Agricultural Science Vol. 9, No. 10; 2017
Thompson, S., Levin, S., & Rodriguez-Iturbe, I. (2013). Linking plant disease risk and precipitation drivers: A
dynamical systems framework. The American Naturalist, 181, 1-16.
Trebicki, P., Nancarrow, N., Cole, E., Bosque-Perez, N. A., Constable, F. E., Freeman, A. J., … Fitzgerald, G. J.
(2015). Virus disease in wheat predicted to increase with a changing climate. Global Change Biology, 21,
Uusiku, N. P., Oelofse, A., Duodu, K. G., Bester, M. J., & Faber, M. (2010). Nutritional value of leafy vegetables
of sub-Saharan Africa and their potential contribution to human health: A review. Journal of Food
Composition Analysis, 23, 499-509.
Van Averbeke, W., Juma, K. A., & Tshikalange, T. E. (2007). Yield responses of African leafy vegetables to
nitrogen, phosphorus and potassium: The case of Brassica rapa L. Subsp, Chinensis and Solanum
retroflexum Dun. Wat e r S A , 33, 355-362.
VanDyck, H., Bonte, D., Puls, R., Gotthard, K., & Maes, D. (2014). The lost generation hypothesis: Could
climate change drive ectotherms into a developmental trap? OIKOS Synthesising Ecology, 124, 54-61.
Van Jaarsveld, P. J., Faberand, M., & Van Heerden, I. (2012). Selected vitamin and mineral content of eight
African leafy vegetables and their potential contribution to individual nutrient requirements. In A. Oelofse,
& W. Van Averbeke (Eds.), Nutritional Value and Water Use of African Leafy Vegetables for Improved
Livelihoods; Water Research Commission TT535/12 (pp. 227-243). Water Research Commission, Pretoria,
South Africa.
Vassiliadis, S., Plummer, K. M., Powell, K. S., Trebicki, P., Luck, J. E., & Rochfort, S. J. (2016). The effect of
elevated co
and virus infection on the primary metabolism of wheat. Functional Plant Biology, 43, 892-902.
War, A. R., Paulraj, M. G., Ahmad, T., Buhroo, A. A., Hussain, B., Ignacimuthu, S., & Sharma, H. C. (2012).
Mechanisms of plant defence against insect herbivores. Plant Signal & Behaviour, 7, 1306-1320.
WHO. (2002). World Health Organisation. Nutrition program: Micronutrient deficiency information system, iron
deficiency anaemia. Genera, Switzerland. Retrieved from
WHO. (2013). World Health Organisation global database on vitamin A deficiency. Vitamin and Mineral
Nutrition Information System (VMNIS).
Woodman, J. D. (2015). Surviving a flood: Effects of inundation period, temperature and embryonic
development stage in locust eggs. Bulletin of Entomological Research, 105, 441-447.
Yang, R. Y., & Keding, G. B. (2009). Nutritional contributions of important African indigenous vegetables. In C.
M. Shackleton, C. M., Pasquini, M. W., & A. W. Drescher (Eds.), African Indigenous Vegetables in Urban
Agriculture (Ch. 4, pp. 10-35). Earthscan, London.
Zhang, W., Chang, X., Hoffmann, A., Zhang, S., & Ma, C. (2015). Impact of hot events at different
developmental stages of a moth: The closer to adult stage, the less reproductive output. Scientific Reports, 5,
Ziska, L. H., & Mcconnell, L. L. (2016). Climate change, carbon dioxide and pest biology: Monitor, mitigate,
manage. Journal of Agricultural and Food Chemistry, 64, 6-12.
Copyright for this article is retained by the author(s), with first publication rights granted to the journal.
This is an open-access article distributed under the terms and conditions of the Creative Commons Attribution
license (
... The constraints in cultivation are the presence of the distraction of pests and diseases that can reduce crop production and quality [5]. Citrus pests and diseases need attention because they can affect productivity and even crop failure, if not managed properly. ...
Full-text available
As a citrus pest, Toxoptera sp. is classified as the main pest because the impact of the attack causes losses to the quantity and quality of the yield. Alternative pest control within insecticides in addition to using a knapsack sprayer or power sprayer is using Bark Pesticide Applicator (BPA), which is a tool to apply systemic pesticides through citrus stems optimally and serves to improve the efficiency of controlling main pests, safe for natural enemies, and environmentally friendly. The study was conducted at the Experimental Farm of the Indonesian Citrus and Subtropical Fruits Research Institute, Batu City, East Java, Indonesia from January to May 2018. This study compared the effectiveness of pesticide application devices using BPA and Power Sprayer (PS). The treatment was arranged using a randomized block design and repeated ten times. The test results showed that the application of pesticides with BPA was able to control aphids up to 93.84 % while PS was only able to suppress 29.48 %. Whiles the existence of natural enemies can be saved if the application of pesticides is carried out using BPA
... Interestingly, the relevance of pest control appeared to be higher than that of diseases for the respondents across Europe. This is in accordance with reports about the spread of pests and diseases and occurrence of new pests arriving from countries outside Europe as a result of climate change and trade globalization [36][37][38], which can affect organic orchards to a higher extent compared to conventional orchards due to the lower number of possible measures and products allowed for their control. ...
Full-text available
There is limited data regarding the specific problems faced by organic fruit growers when dealing with plant protection, particularly at a European Union level, though some general knowledge about pest and disease incidence can be found. Such information is crucial to improve the efficacy of a targeted knowledge transfer to organic fruit growers and advisors aiming at an increased adoption of innovative practices. A survey was thus carried out in seventeen European countries (16 EU member states and Switzerland), within the framework of the EU-funded project BIOFRUITNET, aiming at filling this knowledge gap also in terms of research needs. A questionnaire including a section about general aspects of orchard management (functional biodiversity, fertilization management, varietal/rootstock selection) and a section specifically dedicated to pest and disease occurrence and management in organic orchards was utilized to interview about 250 professionals (farmers and advisors), 155 of which were involved in pome fruits (including apple and pear) production. The analysis of the answers related to plant protection pointed out a varied situation about pest and disease occurrence in apple and pear orchards across Europe, though related to the zonal location of the respondent. However, more than 50% of respondents generally considered just few among the most damaging ones, normally co-occurring in the orchards. Interestingly, regardless of the respondents’ nationality or zonal location, more pests than diseases were indicated as relevant agents threatening organic pome fruits production. Nevertheless, only few measures promoting functional biodiversity in the orchards resulted in being broadly implemented in all regions. The analysis of the data underlines the strong demand for the development of a toolbox of measures that can be integrated successfully into the general orchard management strategy including the successful enhancement of functional or general biodiversity.
... High infestation of pests and diseases limits farmers (apple growers) in obtaining better crop yields and ensuring food as well as nutritional security [61]. Farmers (apple growers) use different chemicals to manage insect pests and diseases; however, there is a huge challenge in that insect resistance is increasingly building up and is becoming a worse constraint to crop management and obtaining good crop yields [62]. ...
Full-text available
Citation: Shah, Z.A.; Dar, M.A.; Dar, E.A.; Obianefo, C.A.; Bhat, A.H.; Ali, M.T.; El-Sharnouby, M.; Shukry, M.; Kesba, H.; Sayed, S. Sustainable Fruit Growing: An Analysis of Differences in Apple Productivity in the Indian State of Jammu and Kashmir.
... High infestation of pests and diseases limits farmers (apple growers) in obtaining better crop yields and ensuring food as well as nutritional security [61]. Farmers (apple growers) use different chemicals to manage insect pests and diseases; however, there is a huge challenge in that insect resistance is increasingly building up and is becoming a worse constraint to crop management and obtaining good crop yields [62]. ...
Full-text available
Apple is considered as an important fruit crop in temperate regions of the world including India. It is one of the major fruit crops, with a considerable area under cultivation throughout the world and a large associated population. Despite this, the productivity of this important fruit is not up to the expected standard. To gain a practical understanding of the low productivity of apple fruit and its probable causes, a study was undertaken to analyze productivity differentials and their determinants to enable sustainable cultivation. A multistage sampling procedure was adopted to select districts, horticultural zones, and villages, and data were collected from randomly selected apple growers (300). The collected data were empirically analyzed with simple descriptive statistics, logistic regression, polynomial plots, and inferential statistics such as t-tests. The results indicated that apple yields followed a sigmoidal pattern, with the average yield per hectare for the current season as 9.43 t/ha, which depends on experience, education, annual income, and the adoption rate of apple growers. This yield average was significantly lower than the yield of the previous season at a probability level of 1%. To determine the root cause of low productivity, different constraints were studied, creating yield disparities in different quarters; hence, their percentage and value contributions (socioeconomic 11.1%, credit 4.2%, pests and diseases 0.05%, technology 0.9%, extension 2.0%, and market 3.5%) were also established in the study. The study will be of great interest to the relevant authorities in the study area, and the areas globally having similar congenial agro-climatic conditions, who are seeking to address the issues raised in this study through sustainable policy decisions. The different constraints that were the fundamental reasons for low productivity and that prevented the apple growers from adopting innovative techniques/improved practices to increase their yields need to be addressed as a matter of urgency.
... and 11.0%-32.4% in wheat, rice, maize, potato, and soybean, respectively (Savary et al., 2019). The FAO reports that the yield damage caused by plant pests and pathogens is about 20%-40% (Phophi and Mafongoya, 2017). Plant pests and diseases have the potential to harm the entire food supply chain and they are often associated with quality deteriorations, resulting in unsafe and inedible food that poses a tremendous public health burden (Hoffmann and Scallan, 2017). ...
Climate change is affecting many facets of our lives and livelihoods, and food production is one of them. While the world population continues to increase, agricultural land and food production are being impacted by climate change at an ever-increasing rate. This chapter looks at climate change and its impacts on agri-food systems and food production. It briefly looks at the science of climate change, some projections, including rainfall and temperature projections to the end of the 21st century, and then is followed by a discussion of impacts of several climate-change–related stressors on agri-food production. Some of the stressors discussed include extreme weather events, such as droughts, floods, cyclones, and heat waves; sea-level rise, including inundation and salinity; invasive alien plant species; pests and pathogens; and neglected and underutilized crop species.
Full-text available
This study examined the impacts of climate change on okra and tomato yields. Fertilizer consumption and credit to the crop sector were considered as covariates in the analysis. Time-series data, spanning a period of 40 years, were obtained from various sources. An autoregressive distributed lag model was applied to analyze short- and long-term impacts of climate change and agricultural inputs on okra and tomato yields. Not all variables were stationary at levels (order zero), but they were all significant at first difference, indicating the presence of cointegration. The Bound’s test F-ratio was statistically significant and implied the presence of long- and short-term relationships among the variables studied. The mean temperatures had negative impacts on okra and tomato yields in both the short and long terms. Credit guaranteed to the crop sector had positive short- and long-term impacts on tomato yield; fertilizer consumption had a negative long-term impact on okra yield. Our study concludes that climate change, particularly rising temperature, impacts herbaceous fruit crop production in Nigeria. Therefore, we recommend that breeding and disseminating climate-smart tomato and okra varieties will help fruit crop farmers respond to rising temperatures.
Full-text available
Adaptive genetic diversity in crop wild relatives (CWRs) can be exploited to develop improved crops with higher yield and resilience if phylogenetic relationships between crops and their CWRs are resolved. This further allows accurate quantification of genome-wide introgression and determination of regions of the genome under selection. Using broad sampling of CWRs and whole genome sequencing we further demonstrate the relationships among two economically valuable and morphologically diverse Brassica crop species, their CWRs and their putative wild progenitors. Complex genetic relationships and extensive genomic introgression between CWRs and Brassica crops were revealed. Some wild B. oleracea populations have admixed feral origins, some domesticated taxa in both crop species are of hybrid origin, while wild B. rapa is genetically indistinct from turnips. The extensive genomic introgression we reveal could result in false identification of selection signatures during domestication using traditional comparative approaches used previously, therefore we adopted a single population approach to study selection during domestication. We used this to explore examples of parallel phenotypic selection in the two crop groups and highlight promising candidate genes for future investigation. Our analysis defines the complex genetic relationships between Brassica crops and their diverse CWRs, revealing extensive cross-species gene flow with implications for both crop domestication and evolutionary diversification more generally.
Full-text available
Grafted vegetable seedlings have been used from the early 20th century. This technique has been utilized extensively in East Asia and the European countries where it has developed as a multimillion-dollar industry. The increase in land area under protected cultivation, intensive use of land, scarcity of production resources and changing climate leading to unpredictable weather has caused a rapid increase in the use of grafted vegetables. However, in Nepal, where the productivity of vegetable crops is quite low and the breeding activities are inadequate, use of grafted vegetables is still unexploited. Therefore, this technique can be an important intervention to improve the overall production system of Solanaceous and Cucurbitaceous vegetables. Methods of vegetable grafting, their current uses, research carried out in Nepal and the possible opportunities are discussed in this review paper. Cleft, splice, tongue approach, hole- insertion and pin grafting are the methods currently in use. Grafting can be used to overcome the problems caused by various soil borne disease and nematodes and abiotic stresses like, low and high temperature stress, water stress, salinity, metal and organic pollutants while increasing the yield and extending crop duration in vegetable production. In Nepal, few research have been carried out on vegetable grafting with majority of them on assessment of tolerance to soil borne diseases. Utilization of this technique in Nepalese conditions provide ample opportunities for researchers and academicians to conduct researches and for breeding companies to develop resistant rootstocks. By implementing this method, vegetable industry can improve the overall yield, its quality and reduce hindrances in production.
Full-text available
Field experiments were conducted in order to study the seasonal incidence of painted bug, Bagrada hilaris at Crop Research Centre (CRC) of G.B. Pant University of Agriculture and Technology, Pantnagar (India) during Rabi seasons of 2015-16. Brassica spp. including Brassica campestris var. brown sarson (BSH-1), Brassica campestris var. yellow sarson (YST-151), Brassica alba var. PSB-I, Brassica carinata var CCN-06-1, Brassica nigra var PBR-I, Brassica juncea (Varuna), Brassica napus (GSC-6) and Eruca sativa (T-27) were sown on five dates starting from October 3 to December 3, 2015, at fifteen days interval. The results show that the infestation of the pest on the crop occurs in two distinct stages, one at the seedling stage and another at the crop maturity stage. B. napus harboured minimum population of Bagrada hilaris while it was higher in B. alba. Regarding sowing date, bug population was the minimum in the trail sown at October, 18 (second sowing) while it was the maximum in Oct 3 (first sowing). The maximum yield of different spp. was found up to third sowing date (Nov 3).
Full-text available
ABSTRACT Insects are powerful and rapid adaptive organisms with high fecundity rate and short life cycle. Due to human interruption in agro-ecosystem and global climatic variations are disturbing the insect ecosystem. Erosion of natural habitats, urbanization, pollution and use of chemicals in agroecosystem manifold the intensity of environmental variations. Both a-biotic (temperature, humidity, light) and biotic (host, vegetative biodiversity, crowding and diets) stresses significantly influence the insects and their population dynamics. In response to these factors insect may prolong their metamorphic stages, survival and rate of multiplication. Insect’s immune responses as melanization, lysozyme level and phenoloxidase (PO) modify the physiology and morphological behavior against different factors like diets, gases and chemicals. Keywords: Gymnopleurus, Karyotype, Chromosomal rearrangements, Scarab beetle.
Full-text available
The diamondback moth (DBM), Plutella xylostella, is a global economic pest of brassicas whose pest status has been exacerbated by climate change and variability. Southern African small-scale farmers are battling to cope with increasing pressure from the pest due to limited exposure to sustainable control options. The current paper critically analysed literature with a climate change and sustainability lens. The results show that research in Southern Africa (SA) remains largely constrained despite the region's long acquaintance with the insect pest. Dependency on broad-spectrum insecticides, the absence of insecticide resistance management strategies, climate change, little research attention, poor regional research collaboration and coordination, and lack of clear policy support frameworks, are the core limitations to effective DBM management. Advances in Integrated Pest Management (IPM) technologies and climate-smart agriculture (CSA) techniques for sustainable pest management have not benefitted small-scale horticultural farmers despite the farmers' high vulnerability to crop losses due to pest attack. IPM adoption was mainly limited by lack of locally-developed packages, lack of stakeholders' concept appreciation, limited alternatives to chemical control, knowledge paucity on biocontrol, climate mismatch between biocontrol agents' origin and release sites, and poor research expertise and funding. We discuss these challenges in light of climate change and variability impacts on small-scale farmers in SA and recommend climate-smart, holistic, and sustainable homegrown IPM options propelled through IPM-Farmer Field School approaches for widespread and sustainable adoption.
Full-text available
The Persian Gulf States (Bahrain. Iran, Iraq, Qatar, Saudi Arabia, Kuwait and UAE) have dominated the oil and gas sector since the discovery of oil in the region. They are the world largest producers of crude oil, producing about 35 and 25 percent of the world natural gas and crude oil respectively. The use of fossil fuels is directly linked to the release of CO 2 into the environment. CO 2 accounts for 58.8 percent of all greenhouse gases released via human activities, consequently, presenting a malign impact on the environment through climate change, global warming, biodiversity, acid rain and desertification among others. Due to its importance, the data on CO 2 emission obtained from US EIA from 1980 – 2008 was regressed using least square techniques and projections were made to the year 2050. Results indicated that each country's p-value was less than 0.05 which implies that the models can be used for predicting CO 2 emissions into the future. The data shows the emission of CO 2 by country from the highest to the lowest in 2016 as: Iran (590.72 Mtonnes; 7.58 tonnes of CO 2 /person) > Saudi Arabia (471.82 Mtonnes; 18 tonnes of CO 2 /person) > UAE (218.58 Mtonnes; 41.31 tonnes of CO 2 /person) > Iraq (114.01 Mtonees; 3.71 tonnes of CO 2 /person) > Kuwait (92.58 Mtonnes; 36.31 tonnes of CO 2 /person) > Qatar (68.26 Mtonnes; 37 tonnes of CO 2 /person) > Bahrain (33.16 Mtonnes; 27.5 tonnes of CO 2 /person) ". The sequence from the country with highest emission (Iran) to the country with lowest emission (Bahrain) will remain the same until 2050. A projection depicting a 7.7 percent yearly increase in CO 2 emission in the Persian Gulf States.
Full-text available
Extensive research has shown that climate change will impact the distribution and outbreak potential of invertebrate pests in broad-acre crops. However, much less attention has been placed on translating these likely changes in pest outbreak frequency into practical management options for growers. Dryland grain production systems are generally predicted to be vulnerable to the effects of climate change. An initial step in understanding changes to outbreak potential of different pests is to describe the spatial distribution of different species and communities. Using a bioclimatic modelling approach, we demonstrate how general patterns of distribution for four major invertebrate pests of Australian dryland grain production systems are likely to be altered by climate change. While such models are useful for predicting the direct impacts of climate change on potential species distributions, they are less useful for assessing pest outbreak frequency from direct or indirect changes. In light of this, we explore different tools that can be used to support adaptive management by farmers to limit the impact of induced pest outbreaks. Primarily, research to increase available information of indirect impacts on the pest species and the communities they interact with, including their natural enemies, is required to extend models of pest outbreak potential. Further, incorporation of pests into global crop models combined with monitoring for existing pests and surveillance for new pests is critical for future pest management decision-making. For natural enemies, generalizations around the impact of climate change and flow on effects for pest control services need to be attempted now. The knowledge of potential management interventions is needed by farmers to support improved management decisions in the short-term, but in some cases will also facilitate adaption to climate change in the long-term.
Full-text available
Climate changes are in response to changes in the hydrosphere, biosphere and other atmospheric and interacting factors. Human activities driven by demographic, economic, technological and social changes have a major impact on climate change. The climate influences the incidence as well as temporal and spatial distribution of plant diseases. The main factors that control growth and development of diseases are temperature, light and water. The climate change affects the survival, vigor, rate of multiplication, sporulation, direction, and distance of dispersal of inoculums, rate of spore germination and penetration of pathogens. Climate affects all life stages of the pathogen and host and clearly poses a challenge to many pathosystems. The environmental change, especially when combined with pathogen and host introductions, may result in unprecedented effects.
Full-text available
Atmospheric CO2 concentrations are predicted to double by the end of this century. Although the effects of CO2 fertilisation in crop systems have been well studied, little is known about the specific interactions among plants, pests and pathogens under a changing climate. This growth chamber study focuses on the interactions among Barley yellow dwarf virus (BYDV), its aphid vector (Rhopalosiphum padi) and wheat (Triticum aestivum L. cv. Yitpi) under ambient (aCO2; 400 µmol mol–1) or elevated (eCO2; 650 µmol mol–1) CO2 concentrations. eCO2 increased the tiller number and biomass of uninoculated plants and advanced the yellowing symptoms of infected plants. Total foliar C content (percentage of the total DW) increased with eCO2 and with sham inoculation (exposed to early herbivory), whereas total N content decreased with eCO2. Liquid chromatography–mass spectrometry approaches were used to quantify the products of primary plant metabolism. eCO2 significantly increased sugars (fructose, mannitol and trehalose), irrespective of disease status, whereas virus infection significantly increased the amino acids essential to aphid diet (histidine, lysine, phenylalanine and tryptophan) irrespective of CO2 concentration. Citric acid was reduced by both eCO2 and virus infection. Both the potential positive and negative biochemical impacts on wheat, aphid and BYDV interactions are discussed.
Full-text available
Significance A key scientific and policy challenge relating to invasive species at the world level is to understand and predict which countries are most vulnerable to the threat of invasive species. We present an analysis of the threat from almost 1,300 agricultural invasive species to the world (124 countries). The analysis examines the global distribution of these species, international trade flows, and each country’s main agricultural production crops, to determine potential invasion and impact of these invasive species. We found the most vulnerable countries to be from Sub-Saharan Africa, while those countries representing the greatest threat to the rest of the world (given the invasive species they already contain, and their trade patterns) to be the United States and China.
The widespread overuse of pesticides in agriculture has generated increasing concerns about the negative effects of pesticides on human health and the environment. Understanding farmers' perceptions of risk of pesticides and the determinants of pesticide overuse is important to modifying their behavior towards reducing pesticide use. A survey of 250 randomly selected smallholder vegetable farmers in Kuwait was conducted to quantify the extent of pesticide use, their pesticide risk perceptions and factors influencing their pesticide use behaviors. The majority of the farmers perceived pesticides pose some risk to the environment (65%) and human health (70.5%), while younger farmers were more likely to perceive this risk than older farmers. When asked to rate how risky pesticides were regarding several aspects of human health and the environment on a scale of 1(not risky) to 5 (extremely risky), concern was highest for the health of applicators (x̅=4.28) and lowest for air quality (x̅=2.32). The risk perceptions of the farmers did not have a positive influence on their pesticide use practices. A total of 76 pesticide active ingredients were found in use, and 9% of these belong to the WHO toxicity class II (moderately hazardous). On average, farmers applied 12.8kg of active ingredients per hectare per year, and 58% of the farmers were found to have overused pesticides, with an average overuse rate of 2.5kg. Pesticide application frequency ranged from two times a month up to once a week, depending on the crop. A binary probit model reveals that farmers' inadequate knowledge of pesticides, the influence of pesticide retailers and lack of access to non-synthetic methods of pest control are positively associated with pesticide overuse, while the propensity to overuse decreases with higher levels of education, training in Integrated Pest Management (IPM) and the safe use and handling of pesticides, and access to extension support. Comprehensive intervention measures for reducing pesticide overuse and limit the health and environmental hazards caused by pesticides are provided in this paper.