**5. Impact of climate change on the insect pest management strategies**

Dramatic changes in the geographical distribution and population development of insect pests, interactions between insect-host plants, the behaviour and abundance of natural enemies, and the efficacy of crop defence technologies may be caused by global warming and climate change. As a consequence of global warming, the distribution and relative abundance of some insect species susceptible to increase in temperatures in the temperate regions may decrease, while insect pests currently confined to the tropical and subtropical regions may migrate to the temperate regions along with a shift in the production areas of their host plants. As a consequence of global warming and climate change, the relative effectiveness of pest control strategies is likely to change. There is an immediate need to evaluate, under varying environmental conditions, the efficiency of different IPM technologies and develop suitable strategies for mitigating the adverse effects of climate change [70].

Although some impacts of climate change may be optimistic, evidence indicates that pest issues are likely to become more volatile and greater in amplitude overall.

However, due to the complex interacting factors of increasing CO2 levels, shifting climate regimes and altered frequency/intensity of extreme weather events, predicting the impact of climate change on insect pests is not simple [71]. In addition, differences in the thermal preferences of insects and their natural enemies may result in a lack of cooperation between the two and an increased risk of host outbreaks [72]. Changes in the effectiveness of methods of insect pest control as well as changes in policies of land use and crop management are the result of other indirect responses to insect pests, which can also have a higher impact on the pressure of insect pests than the direct effects of climate change alone. A few examples of direct and indirect effects are the following impacts on insect pests if changing climate conditions are studied in isolation:

#### **5.1 Increases in temperature**

The severity of damage caused by insect pests may be increased by increases in temperature. In USA, where increasing temperatures leading to greater insect populations in southern regions have bring about in higher use of insecticides compared to colder, higher latitude provinces, such growing insect populations and pressures will lead to more frequent insecticide applications. Such upsurges of toxic chemical applications may have serious adverse effects on human and environmental health. Temperature changes can also decrease the efficacy of some insecticides, such as a decrease in the toxicity of lambda-cyhalothrin, bifenthrin and spinosad to *Ostrinia nubilalis* as a result of elevated temperature after exposure [73]. The effectiveness of parasitoids in the control of pest species and the expression of defensive characteristics used by insect pests against their larval parasitoids has been found to affect even with minor variations in thermal conditions [74].

## **5.2 Altering precipitation**

Extreme or insufficient precipitation can have a major impact on crop and pest interactions, as hot and humid conditions favour many species that are highly susceptible to moisture and rainfall. Also, as found during floods in Iowa in 1993, water-stressed crops are more likely to be affected by pests [75]. Changes in precipitation events are compounded by outbreaks of desert locusts, as demonstrated by their incursion of greater than 10 countries in northern and western Africa in 2004 after heftier than usual rainfall, resulting in severe crop injuries and food scarcities. Locust epidemics are only expected to become more common as the frequency and severity of precipitation events are predicted to increase in the future.
