It is mid-July so if foliage feeding caterpillars have not shown up in your peanut field yet, they likely will soon! Two types of caterpillars commonly found in Columbia County July-September are the velvetbean caterpillar and soybean looper. It is important to properly identify the caterpillars in your field to determine management decisions. Velvetbean caterpillars are usually cheaper to manage and can be controlled with many different insecticides (Belt, Besiege Blackhawk, Coragen, Diamond, Dimilin, Intrepid, and Radiant. Along with pyrethroids: Asana, Besiege, Baythroid, Brigade, Mustang Max, Proaxis, etc). There are fewer options available to control soybean loopers (Belt, Besiege, Blackhawk, Coragen, Diamond, Intrepid, Prevathon, Radiant, and Steward). Note that pyrethroids are not recommended for soybean looper control and have the potential to flare spider mites especially in non-irrigated peanuts.
Unfortunately, velvetbean caterpillars and soybean loopers look similar. However, counting the number of legs or “abdominal prolegs” in the caterpillar’s midsection can be used for identification purposes. The velvetbean caterpillar has 4 pairs of abdominal prolegs while the soybean looper has 2 pairs of abdominal prolegs. Make sure you are only counting the pairs of abdominal prolegs (or the pairs of legs in the caterpillar’s mid-section) and not the anal prolegs at the end of the caterpillar!
The economic threshold, or the number of caterpillars per foot, that justifies an insecticide application is 4-8 caterpillars per foot of row. Make sure to check multiple locations throughout the field (approximately 10 representative locations) when determining the economic threshold. Often, hot spots can be found that exceed the economic threshold when most of the field has caterpillar populations below threshold.
Refer to South Carolina Pest Management Handbook for Field Crops for additional information on insecticide options for peanut pests:
The commercial products listed are possible recommendations to help manage foliage feeding caterpillars in peanut production. This blog post is intended for educational purposes. It is not the intention of the author to provide a complete list of product recommendations or endorse a particular product or brand.