Impact of Climate Change on Insect pests behavior
Dr. Hadi Husain Khan1, Dr. Akhtar Ali Khan2, Dr. Mohd. Monobrullah3, Dr. Anjani Kumar4, Dr. Ashok Kumar Sharma5, Habibul Haque6 & Nirmal Chandra Ghose7
1Research Associate, ICAR-DRMR-APART, Dhubri -783324 (Assam), India.
2Professor, Division of Entomology, SKUAST, Kashmir,Shalimar,Srinagar – 190025 (J&K), India.
3Principal Scientist, Division of Crop Research, ICAR-RCER, Patna- 800014 (Bihar), India.
4Director, ICAR-ATARI, Zone – IV, Patna- 801506 (Bihar), India.
5Principal Scientist (Ag. Extension), ICAR-DRMR,Bharatpur (Raj.) – 321303, India.
6District Agricultural Officer-Cum-Project Director, ATMA, Dhubri – 783324 (Assam), India.
7SDAO (HQ)-Cum-Nodal Officer, ICAR-DRMR-APART, Dhubri – 783324 (Assam), India.
Insects are cold-blooded (poikilothermic) organisms – the temperature of the insect bodies is approximately the same as their surrounding environment. The temperature is the most important environmental factor influencing insect distribution, behaviour, development, survival, and reproduction. Predict the impact of climate change on insects is a very complex effect and one that involves a great deal of modelling. There have been some rather amazing documented cases of how climate can influence insect populations.
Increased temperature could increase insect pest populations:
Temperature can impact on insect physiology and development directly or indirectly through the existence of hosts. Increasing temperature can potentially affect the geographic range, insect survival, development, and population size. It has been estimated that 2oC temperature increase the one to five additional life cycles per season. Some of the insects take several years to complete one life cycle – these insects (cicadas, arctic moths) have a tendency to moderate temperature variability over the entire of their life history.
We often use degree-day based models to predict the emergence of these insects and their ability to damage the crops (cabbage maggot, onion maggot, European corn borer, Colorado potato beetle).
Natural enemy and host insect populations may respond in a different way to changes in temperature. Hosts may pass though susceptible life stages more quickly at higher temperatures, reducing the window of opportunity for parasitism. Temperature may change gender ratios of some pest species such as thrips potentially affecting reproduction rates.
Increased temperature could decrease pest insect populations:
Some insects are closely attached to a specific set of host crops. Increasing temperature that farmers not to grow the host crop for longer period would decrease the populations of insect pests specific to those crops. The same environmental factors that impact on insect pest can impact their natural enemies and parasites as well as the insect pathogens that attack on insect populations., Aphids have been shown to be less responsive to the aphid alarm pheromone at higher temperatures, they release when it is attack by insect predators and parasitoids – resulting in the potential for greater predation.
How changes in precipitation will affect insects?
Some of the insects are sensitive to precipitation and are removed or killed from crops by heavy rains – in some north eastern US states, this consideration is important when choosing management options for onion thrips. Other insects such as pea aphids are not tolerant to drought.
How changes in humidity will affect insects?
Distinct temperature, there are no definite ranges of favourable relative humidity to all insects. Different species and their immature stages have their own range. Humidity affects the speed of development, fecundity, colour etc. If water content is high in insect body, dry air accelerates the development. Locusts sexually mature quicker and the numbers of eggs laid are more at 70% R.H. Rhinoceros beetle develops light chitin in dry air and dark chitin in moist air. Survival is indirectly affected due high humidity conditions that favour the spread of diseases in insects.
How rising CO2 levels affect insects:
Global warming, mainly due to elevated CO2 this can increase levels of simple sugars and decrease the nitrogen contentin leaves, also increase the damage caused by many insects, which consume more leaves for their metabolic requirements of nitrogen. Depending on the pest, elevated CO2 may act in a synergic or conflicting manner with higher temperatures. Results of such interactions are difficult to be estimate. Therefore, one is important to wait for visual appearance of a pest for initiating action.ElevatedCO2 levels and higher temperatures will keep changing the composition and duration of infective stages of pests.
How this will affect farmers:
It is likely that farmers know very well extensive impacts on insect management strategies with changes in climate. Insecticides applications have significant economic costs for growers and environmental costs for society. Additionally, at higher temperatures some classes of pesticides (pyrethroids and spinosad) have been shown to be less effective in controlling the insect pest.
What farmers can do to adapt?
Farmers who continuously monitor the occurrence of pests in their fields and keep the records of severity, frequency, and cost of managing pests over time will be in a better position to make decisions about climate change, it remains economical to continue to grow a particular crop or use a certain pest management technique. If more insecticide applications are required in order to successfully grow a particular crop, farmers will need to carefully evaluate whether growing that crop remains economical.
The effects of climate change on insect pest communities result in increased herbivores and decrease the abundance of decomposers and predators, which may have negative impact on entire ecosystems. The indiscriminate use of insecticides resulting from an increase in pest outbreaks will likely have negative environmental and economic impacts for agriculture. The best economic strategy for farmers to follow integrated pest management (IPM) practices such as field monitoring, pest forecasting, recordkeeping, and choosing economically and environmentally safe control measures will be most likely to be successful in dealing with the effects of climate change.
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