Farmers love to talk about the weather, but do you realize just how much it influences crop pests?
Intuitively, we know that temperature affects insect development. Tools such as growing-degree-day calculators are now common, and very useful, for estimating activity.
But think bigger; think global!
Many pest insects, especially aphids and moths, utilize spring low-level jet streams (LLJ) as a means of dispersal. In fact, these LLJs can carry the insects substantial distances. For large-bodied, strong flying moths, estimates range from 100-500 km (60-300 mi) per night!
Why do insects migrate? Most agree that the answer lies in a combination of biotic and abiotic factors. Overcrowding and the constant need to pursue resources (FOOD!) are obvious. Some other factors that initiate migration include:
- Stormy weather
- Abnormally high or low humidity
- Incr. atmospheric electricity
- Daylength cues
Science has come a long way in measuring insect migrations. Take, the iconic locust for example. Faure (1932) proposed that nymphal crowding might influence the need for dispersal. The research concept was furthered by Gunn (1960), as he described in detail the migratory patterns and population dynamics. One of the first theorists on the effect of large-scale weather processes on insect ecology was W.G. Wellington (1954).
A key benefit to understanding meteorological processes and how they influence pest activity is that new, modern methods can be deployed to forecast and predict biological phenomena such as mass migration and invasion.
With the development of LiDar, vertical radar, and geostatistics, this fascinating subject is becoming more understood. If you are interested in knowing more, this is a good introductory resource, which is built upon in this paper. Some of my favorite papers can be found here and here.