Inundated=Overwhelmed with things to deal with. We have been hard hit by caterpillars the last 2+ weeks. Starting with Soybean loopers about 14 days ago, and continuing with Velvetbean caterpillar (VBC) the last week. We are well above threshold levels in many peanut and soybean fields locally.
Knowing the difference is very important. Control measures required can range from $1 to $10 per acre or more. You also don’t want to return to the field in 10 days and realize your chemical was wasted, and your vines or bushes are just skeletons remaining. Although both these caterpillars look alike to the casual observer, identification is simple. Caterpillars have legs, which we call “prolegs” under their belly that can help us with identification. These species are going to have 2 pairs of thoracic prolegs, those are the pairs closest to the head. Farther towards the tail, we will find 4 pairs of abdominal prolegs on the Velvetbean caterpillar. The Soybean looper will only have 2 pairs of abdominal prolegs. Each of these species will also have one pair of anal prolegs on their last segment. Sometimes people don’t compare apples and oranges when counting prolegs and may include anal prolegs in their counts. For identification, let’s just count the abdominal prolegs, which are separated by a gap from the anal prolegs.
Some people joking lay say that VBC can be killed by saying the word “insecticide.” The list of options to control them is long, including pyrethroids that should cost about $1 per acre. On the other hand, the products to control Soybean looper are few. Belt, Steward, and Intrepid have worked well this year in our area, but these come at a much steeper price tag. It is important to identify your pest correctly. These are both voracious feeders, and if you miss them one week, you may not have many leaves left on the plant the next week.