Bean Leaf Beetle feeding on early emerging soybeans
Does the mild winter we had in much of the Corn Belt mean insect pressure will be abnormally high this spring and summer? It is possible, but several factors come into play. Even though the winter temperatures were quite mild, we also lacked significant snow cover for extended periods. A lack of insulating snow cover can actually make insects that overwinter above ground more susceptible to freezing temperatures at the soil surface compared to a year when a snow blankets and insulates the soil surface for many of the winter months. Insects that overwinter below ground may have higher survival rates if the soil frost layer is shallow. Insect development is driven by temperature (heat units) just like our crops. The warmer it is early in the year, the faster the insects will develop and begin to break winter dormancy. All of these 75+ degree days in March may cause some insect populations to become active early. Will there be a food source readily available for them if crops are not planted yet? Large temperature swings can be detrimental to insects. If we were to endure a drastic cold spell soon after insects break winter dormancy, it may aid in insect mortality but also stresses crop stand establishment.
In summary, it’s possible that insect pressure could be above normal this year depending on your geography and crop rotation. Although we lacked an insulating snow cover for significant periods this winter, we also just didn’t have extended periods with subfreezing temperatures and many areas did not record a single day with low temperatures at or below zero degrees. Be in your fields early and often this year in order to evaluate any chance for increased insect pressure and to assure a timely treatment if effective and warranted. Those insects causing early stand loss can often have a direct negative impact on yield potential of your crop. It should also be noted that for insects that primarily do their damage well below the soil surface, your best and often only effective treatment is prior to or at planting as a preventative. Rescue treatments in season for insects such as grubs and wireworms are generally not effective. If you have questions as you get into your fields, contact your local Hoegemeyer District Sales Manager or Area Agronomist.