Climate change driven pest management strategies Climate change Impacts of climate change on insect pest scenario Pest Mana...
Climate change driven
pest management strategies
- Climate change
- Impacts of climate change on insect pest
scenario
- Pest Management Adaptations to Changing
Pest Scenario
- Conclusion
Being a
tropical country, India is more challenged with impacts of looming climate
change. Over past hundred years, the global temperature has increased by 0.8ºC
and is expected to reach 1.1-5.4 ºC by the end of next century. On the other
hand, CO2 concentration in the atmosphere has increased drastically
from 280 ppm to 370 ppm and is likely to be doubled in. There has been a lot of
discussion on the effects of climate change on plant productivity and
experiments indicate that higher levels of CO2 generally
increase productivity of plants. However this can be countered by effects
mediated through high temperatures and reduced water availability. There is
already evidence that these factors are having a negative impact on
productivity of grains and other rather than a positive effect.
Apart
from having direct effects on plant productivity, climate change can also
influence productivity through indirect effects mediated by changes in pests
and diseases. Insect-pests of crop plants are the real candidates most affected
by global climate change. Complex physiological effects exerted by the
increasing temperature and CO2 may
affect profoundly, the interactions between crop plants and insect-pests.
Climate
change driven global warming is affecting the distribution, demography and life
history of many species, particularly insects. It is also influencing the
phenology of insects including arrival times and emergence time of a range of
insects. These changes are having, and will have, consequences for human
livelihoods, including an increased spread of pest and diseases of important
crops. Following are the notable effects of climate change on insect pest scenario
and pest population dynamics.
1.
Expansion of geographic ranges
Altered
temperature and rainfall regimes with the predictable changes in climate will
determine the future distribution, survival and reproduction of the species.
With rise in temperature, the insect-pests are expected to extend their
geographic range from tropics and subtropics to temperate regions at higher
altitudes along with shifts in cultivation areas of their host plants. This may
lead to increased abundance of tropical insect species and sudden outbreaks of
insect-pests can wipe out certain crop species, entirely. At the same time;
warming in temperate region may lead to decrease in relative abundance of
temperature sensitive insect population. In future, projected climate warming
and increased drought incidence is expected to cause more frequent insect
outbreaks in temperate regions also.
Range
extension in migratory species like Helicoverpa armigera (Hubner),
a major pest of cotton, pulses and vegetables in North India is predicted with
global climate warming. Subsequently, these ongoing shifts in insect-pest
distribution and range due to changing climate may alter regional structure,
diversity and functioning of ecosystems.
2.
Increase in number of generations
As
temperature being the single most important regulating factor for insects.
Global increase in temperature within certain favourable range may accelerate
the rates of development, reproduction and survival in tropical and subtropical
insects. Consequently, insects will be capable of completing more number of
generations per year and ultimately it will result in more crop damage.
3. Risk
of introducing invasive alien species
According
to the Convention on Biological Diversity (CBD), invasive alien species are the
greatest threat to loss of biodiversity in the world and impose high costs to
agriculture, forestry and aquatic ecosystems by altering their regional
structure, diversity and functioning.
It is
expected that global warming may exacerbate ecological consequences like
introduction of new pests by altering phenological events like flowering times
especially in temperate plant species as several tropical plants can withstand
the phenological changes. Invasion of new insect-pests will be the major
problem with changing climate favouring the introduction of insect susceptible
cultivars or crops.
4. Impact
on pest population dynamics and outbreaks
Changes
in climatic variables have led to increased frequency and intensity of
outbreaks of insect-pests. It may result in upsetting ecological balance
because of unpredictable changes in the population of insect-pests along with
their existing and potential natural enemies. Outbreak of sugarcane woolly
aphid Ceratovacuna lanigera Zehntner in sugarcane belt of
Karnataka and Maharashtra states during 2002-03 resulted in 30% yield losses.
These situations of increased and frequent pest damage to the crops have made
another big hole in the pockets of already distressed farmers by increasing the
cost of plant protection and reducing the margin of profit.
5.
Breakdown of host plant resistance
Expression
of the host plant resistance is greatly influenced by environmental factors
like temperature, sunlight, soil moisture, air pollution, etc. Under stressful
environment, plant becomes more susceptible to attack by insect-pests because
of weakening of their own defensive system resulting in pest outbreaks and more
crop damage. Thermal and drought stress associated breakdown of plant
resistance have been widely reported. With global temperature rise and
increased water stress, tropical countries like India may face the problem of
severe yield loss in sorghum due to breakdown of resistance against midge Stenodiplosis
sorghicola (Coq.) and spotted stem borer Chilo partellus Swinhoe.
The
environmental factors like high temperature have been found affecting transgene
expression in Bt cotton resulting in reduced production of Bt toxins, this lead
to enhanced susceptibility of the crops to insect-pests like bollworms
viz., Heliothis virescens (F.), Helicoverpa armigera (Hubner)
and Helicoverpa punctigera (Wallen).
6.
Increased incidence of insect vectored plant diseases
Climate
change may lead to more incidence of insect transmitted plant diseases through
range expansion and rapid multiplication of insect vectors. Increased
temperatures, particularly in early season, have been reported to increase the
incidence of viral diseases in potato due to early colonization of
virus-bearing aphids, the major vectors for potato viruses in Northern Europe.
1.
Breeding climate-resilient varieties
To
minimize the impacts of climate and other environmental changes, it will be
crucial to breed new varieties for improved resistance to abiotic and biotic
stresses. Considering late onset and/ or shorter duration of winter, there is chance
of delaying and shortening the growing seasons for certain Rabi/ cold season
crops. Hence we should concentrate on breeding varieties suitable for late
planting and those can sustain adverse climatic conditions and pest and disease
incidences.
2. Alternation
in sowing dates of crops
Global
climate change would cause alternation in sowing dates of crops which alter
host-pest synchrony. There is need to explore changes in host plant interaction
under early, normal and late sown conditions in order to recommend optimum
sowing dates for reduced pest pressure and increased yield.
3.
Rescheduling of crop calendars
As such,
certain effective cultural practices like crop rotation and planting dates will
be less or non effective in controlling crop pests with changed climate. Hence
there is need to change the crop calendars according to the changing crop
environment. The growers of the crops have to change insect management
strategies in accordance with the projected changes in pest incidence and
extent of crop losses in view of the changing climate.
4. GIS
based risk mapping of crop pests
Geographic
Information System (GIS) is an enabling technology for entomologists, which
help in relating insect-pest outbreaks to biographic and physiographic features
of the landscape, hence can best be utilized in area wide pest management
programmes. How climatic changes will affect development, incidence, and
population dynamics of insect-pests can be studied through GIS by predicting
and mapping trends of potential changes in geographical distribution of
agro-ecological hotspots and future areas of pest risk.
5.
Screening of pesticides with novel mode of actions
It has
been reported that, application of neonicotinoid insecticides for controlling
sucking pests induces salicylic acid associated plant defense responses which
enhance plant vigour and abiotic stress tolerance, independent of their
insecticidal action. This gives an insight into investigating role of
insecticides in enhancing stress tolerance in plants. Such more compounds needs
to be identified for use in future crop pest management.
In
addition to the strategies discussed above, we need to decide the future line
of research and devise policies for combating the pest problems under climate
change regimes. Some of these are
- Evolve temperature tolerance
strains of natural enemies
- Development of Weather and pest
forecasting models
- Developing early warning
systems/decision support systems
- Awareness regarding impacts of
climate change
- Adoption of mitigation and adaptation
measures
- Sensitization of stakeholders
about climate change and its impacts
- Farmers’ participatory research
for enhancing adaptive capacity
- Promotion of resource
conservation technologies
In India,
pest damage varies in different agro-climatic regions across the country mainly
due to differential impacts of abiotic factors such as temperature, humidity
and rainfall. This entails the intensification of yield losses due to potential
changes in crop diversity and increased incidence of insect-pests due to
changing climate. It will have serious environmental and socio-economic impacts
on rural farmers whose livelihoods depend directly on the agriculture and other
climate sensitive sectors.
Dealing
with the climate change is really tedious task owing to its complexity,
uncertainty, unpredictability and differential impacts over time and place.
Understanding abiotic stress responses in crop plants, insect-pests and their
natural enemies is an important and challenging topic ahead in agricultural
research. Impacts of climate change on crop production mediated through changes
in populations of serious insect-pests need to be given careful attention for
planning and devising adaptation and mitigation strategies for future pest
management programmes.
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