Update from the Field: Cold Weather Bugs Me
Posted by David Dyson, Agronomist on January 08, 2018
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The last couple of weeks of extremely cold weather has brought up some questions as to how insect pests will react to this situation. Insects are cold-blooded animals, meaning that their body temperature is similar to that of their surroundings. They do not maintain a body temperature as do mammals and birds. Insects survive the winter as eggs, pupae, larvae or, in some cases, as adults in tiny micro habitats in leaf litter, the ground, and bark on trees. Remember that snow, ice, and residue are insulators. For example, when there is a -17° F day, things that are covered with residue, snow or ice will remain much nearer to 32° F, providing a measure of protection from the ultra-cold temperatures.
We should look at row crop pests in two categories, cold-adapted and migratory insects. European corn borer larvae and soybean aphids are great examples of cold adapted insects. European corn borer can survive -4° F for three continuous months, while the egg stage of the soybean aphid can survive to about -29° F in a single severe cold event. Corn rootworm eggs, on the other hand, can be very sensitive to low temperatures. When corn rootworm eggs are exposed to temperatures below 18° F, they will have a greater chance of becoming non-viable the following crop season. The deeper the corn rootworm eggs are laid in the soil, the more insulated from temperature variations the eggs become. The importance of seeking a “hiding place” for eggs or larvae is illustrated by a study conducted by Purdue University near Evansville, IN. Temperatures inside corn root crowns were measured over three winters. Although air temperatures fell below -2.2° F for up to five consecutive days, root crown temperatures only approached 18° F for periods of a few hours.
Migratory insects such as armyworm, black cutworm, and leafhooper will overwinter in the south and migrate north to lay eggs to continue their life cycle. These insects will not be affected by local or regional weather in the winter months. They will be affected by late or early springtime weather. If the spring warms up early, these pests can start their migration earlier and can be very challenging to smaller, younger plants.
In conclusion, extreme cold weather in the winter months can affect the population of some overwintering pests. Corn rootworm eggs that are laid in shallow soil will most likely not survive, but any eggs laid deeper will survive and cause plenty of trouble. Corn rootworm larvae will emerge more uniformly and may be later than normal. The insect population might decrease by a very small amount, but these nasty critters have learned to hide and adapt to whatever Mother Nature throws at them.
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Dave Dyson is a regional agronomist for The Andersons’ Farm Centers which are located throughout Ohio, Michigan, and Indiana. He is an Indiana native and grew up on a dairy farm in Miami County. A graduate of Purdue University with a degree in Crop & Soil Science, Dave has a deep knowledge of various agronomic topics and is committed to helping growers improve their crops. If you have any questions, Dave can be reached at david_dyson@andersonsinc.com.
