Treat when you catch an average of 1.5 foliage feeding worms per sweep. Soybean loopers are harder to dislodge with a sweep net and each looper should be counted twice. Each larva eats a high percentage of the total amount of foliage it consumes during the last 4 to 5 days of the larval cycle. If disease is present in the population growers may wish to delay application for 2 to 3 days, especially if larvae are less than a half inch long and populations are not much above the minimal threshold. Both fungal and viral disease can wipe out a caterpillar infestation within a week under the right conditions. Podworm and stink bug numbers have been below threshold levels thus far in the vast majority of soybean fields. However soybeans planted behind wheat could see increasing populations of these two pests as we enter the pod-fill stage. Three-cornered alfalfa hopper (3CAH) numbers are variable (usually less than 2 per sweep) but numbers in most untreated fields are increasing. Some growers who applied a fungicide to their soybeans have also included an insecticide to reduce 3CAH numbers. As soybeans mature we will see more fields with multiple insect pest species present. At times there will be 2 or more species at densities which are just below treatment threshold levels. It can be difficult to make a treatment decision in this situation. If you need assistance in making a soybean treatment decision you can call me at 256-627-3450.
By: Tim Reed