Climate Change and Insects
Predicting the impact of climate change on insects and diseases is a very complex exercise and one that involves a great deal of modeling. There have been some rather spectacular documented cases of how climate can influence insect populations. One good example getting press right now is the mountain pine beetle situation on the West Coast. We don't have all of the answers where climate change is concerned. But in many cases, we can make some good generalizations about larger trends that might be observed.
Climate plays a critical role in the ability of insects to overwinter (a subject we covered in the first issue of Hort Matters for 2006), on the geographic distribution or ranges of insects, on the number of generations and on their abundance in agricultural systems.
As we tell our scouts during training sessions every year, temperature is one of the driving forces affecting insect survival, development and movement. Insects have adapted many mechanisms to survive adverse conditions such as winter by seeking shelter, entering a dormant stage called diapause, or like the Canadian "Snow Birds", by migrating to warmer places.
Where an insect chooses to overwinter may affect its survival. For example, some insects overwinter near the soil surface. In this case, snow cover can provide an excellent insulation, and if this is reduced, these insects might not survive a very cold winter. On the other hand, an increase in temperature and a longer growing season could result in an extension of ranges of plants and animals, with new insects being able to establish themselves in a region where they were previously unable to survive.
So what's the problem with that? New pests would require the development of monitoring programs, the establishment of action thresholds and the availability of new pest control products and strategies for IPM. All of these things take time to develop.
Similarly, an increase in the number of generations can translate into the need for additional controls and would present challenges to resistance management. Some insects that are normally secondary pests might also become more serious.
Altered wind patterns could affect the long distance movement of some species that do not overwinter in Ontario that are picked up and moved by weather fronts. Since many insects are vectors of plant diseases, subtle changes in climate could affect the incidence of transmission.
There are still many unknowns in the climate change equation. The general consensus is that extremes of temperature will become more common. With an overall warming trend, insect woes just might increase in Ontario. Pest management strategies in agriculture and forestry will require adjustment.
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