When it comes to insecticides in corn and soybeans, it's important to remember that different pests are present at different points in the season. Whether or not an insecticide is warranted can be determined by a few factors. 

When it comes to insecticides in corn and soybeans, it's important to remember that different pests are present at different points in the season. Whether or not an insecticide is warranted can be determined by a few factors. What insects are present? Does this field have a history of a particular insect pest? Are these insects present at a level that will impact your yield and ROI?

Black cutworm is usually the most damaging cutworm species found in the Corn Belt.

Economic damage is more likely when weed hosts, such as winter annuals, are killed at or just before planting. This causes the cutworms to leave their host plant and relocate to the emerging corn crop.

Black Cutworm, Armyworm spp., Stalkborer,  Seed Corn Maggot, Beetles, and Wireworm

Bean Leaf Beetle (larvae), Grubs, Seed Corn Maggot, Beetles, and Wireworm

Late-season foliar insecticides have shown the potential to provide synergistic effects when applied with fungicides. For this reason, many farmers choose to apply this combination of products, while others choose to apply insecticides based off of economic thresholds.

When we think of stink bugs creating issues in soybeans, we primarily think of the green stink bug. The green stink bug can produce multiple generations in a single crop season. The stink bug feeds on pods and the developing seed by puncturing tissue with their mouth. Stink bugs prefer to feed on developing seed pods which can result in shriveled and deformed seeds. In some cases, abortion of the seed has been observed.

Stink bug thresholds tend to be lower than other insects as they can quickly cause significant damage to seed numbers and seed quality. Consider treatment once you detect four or more adults or nymphs collected with ten sweeps of a sweep net. If the soybeans are food-grade or for seed quality, this threshold is reduced to two adults or nymphs detected per ten sweeps.

Although we have focused on the control of insects and the use of insecticides, we do know from previous research that a combined application of an insecticide and fungicide can result in a synergistic or net greater effect. In other words, 1+1 does not equal 2 in this case but is more like 3 or greater with the combined application of both products. Reference the PFR Proven™ soybean fungicide handout for a list of soybean fungicides that have worked at our PFR sites!

Bean Leaf Beetle, Japanese Beetle, Leafopper spp., Soybean Aphid, Grasshopper spp., and Stink Bug spp.

Bean Leaf Beetle, Japanese Beetle, Mexican Bean Beetle, Soybean Aphid, and Stink Bug spp.