Don Vick and I looked a quite a few cotton, peanut and soybean fields yesterday. We observed the most insect pressure in soybeans. This field is around R5, beginning seed stage. Walking in the field, it was easily to note the leaf damage. At this growth stage, 15% leaf damage is our threshold. I always like to do a ground cloth sample. If you sit down in the row and shake soybeans, you can count insects per row foot. I also used a sweep net.
This field needed to be treated based on foliage feeding insect thresholds. The caterpillars we were finding were soybean loopers and velvetbean caterpillars. VBC has 4 pair of abdominal prolegs and wiggles when disturbed. We had to check recommendations since soybean looper is resistant to pyrethroids and Steward does not have good activity on VBC. Also, they mixed another fungicide with it for Asian Soybean Rust. Here is an example of threshold for foliage feeders in soybeans: