Soybean Pests: Bean Leaf Beetles and Podworms

The two most common, and potentially yield-reducing, pests in soybeans are bean leaf beetles and “podworms,” which both may feed on the marketable product, the bean. “Podworm” is a generic name for any worm (moth larva) that feeds on soybean pods. These can be corn earworms (probably most common), armyworms, fall armyworms, yellow-striped armyworms, or a combination of these.

There is a huge difference in “podworm” feeding vs. adult bean leaf beetle feeding (see Figure 1). First, adult been leaf beetles (Figure 2) feed on the pod, and will feed on any green pods as long as there are green pods in the field. So, from pod set until all pods have dried down in the fall, adult bean leaf beetles can feed on pods, causing the beans to dry down or fall out, or making them more susceptible to pathogens. These beetles can transmit bean pod mottle virus disease, but fortunately, this has not been common in Kansas. Treatment may be justified if three or more beans are destroyed/plant.

Figure 1. Soybean pod feeding damage by Bean leaf beetles. Photo by K-State Entomology.

Figure 2. Adult bean leaf beetles. Photos by K-State Entomology.

Podworms (Figure 3), on the other hand, only feed on the bean or seed, within the pod, and for only the 2 weeks when they are in the larval stage. Thus, if pods have holes where beans should be, that is indicative of podworm feeding. So, there may be 1, 2, or 3 holes per pod, with no bean inside. If there are only holes, but no worms, the larval feeding stage has past and thus it is too late for an insecticide treatment. Field scouting should start as plants begin to set pods, and, hopefully, larval feeding on beans is detected early, before much feeding damage has occurred. Treatment may be justified at one small larva per row foot.

Figure 3. Soybean podworm feeding on a soybean plant. Photo by K-State Entomology.

 

For more information on soybean insect pest management, please refer to the 2026 K-State Soybean Insect Pest Management Guide at https://bookstore.ksre.ksu.edu/item/soybean-insect-pest-management-2026_MF743

 

Jeff Whitworth, Entomology Extension Specialist
jwhitwor@ksu.edu