Soybean podworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), also known as corn earworm and cotton bollworm, is an important pest of soybeans in southern and eastern states. In Missouri, it is most problematic in late-planted soybeans, especially in counties in the southern part of the state.

The larvae vary in color but are typically marked by several dark longitudinal stripes running along their bodies. There are also numerous black bumps with protruding hairs that will be present on the top and sides of their bodies. Additionally, podworm larva has four pairs of abdominal prolegs and one pair of anal prolegs. Larvae feed on soybean foliage, pods, seeds, and flowers (Figure 1).

Soybean podworm larva on a soybean leaf. (Photo by Jeova Da Silva)

In Missouri, soybean podworm overwinters as pupae in the soil. Additionally, each spring, podworm moths (Figure 2) migrate into Missouri from the southern states. This pest has three generations per year in Missouri, and the second and third generations are most damaging to soybeans. This is the time of the year when rowers should begin scouting their fields for podworm presence. Scouting can be done using a drop cloth or a sweeping net. Economic thresholds for treatment vary depending on scouting method, soybean market price, and control costs. An online economic threshold calculator is available (https://soybeans.ces.ncsu.edu/wp-content/uploads/2017/08/CEW-calculator-v0.006.html) to help determine when insecticide application is warranted.

Figure 2 Soybean podworm moth. (Photo by Jeova Da Silva)