Updated bean leaf beetle thresholds

Summer is winding down fast, but some areas in Iowa still have respectable numbers of bean leaf beetle. The second generation is coming out and could cause direct injury to soybean pods. If your beans are still developing, it might be a good time to go out and take some sweeps.

 Bean leaf beetles can be confused with southern corn rootworm and other beetles. Look for four dark spots on the forewings, and a dark triangle behind the "neck." Photo by Marlin E. Rice. 

Overwintering and first generation bean leaf beetles rarely cause direct economic damage to soybean in Iowa; plants compensate for defoliation in many ways. But they can transmit bean pod mottle virus that can impact the market value of food grade soybean. Bean leaf beetle can cause direct injury to pods during the seed fill stage depending on when the second generation emerges. 

Bean leaf beetles can eat about 0.2 pods per day. Note they don't eat all the way through the pod, like grasshoppers can. Photo by Mark Licht, ISU Extension. 

Last year I had several questions about treatment thresholds for bean leaf beetle given our higher market values. With the help of ISU entomology grad student, Mike McCarville, we created a dynamic threshold calculator. It's a downloadable Excel file where you plug in your market value and control costs. Visit this ICM News article and scroll to the bottom for the link the calculator. To learn more about bean leaf beetle biology and management, click here.

Bean leaf beetles are hungry

In March, I predicted low overwintering mortality based on our mild winter. You may have noticed adults become active in alfalfa starting in April. Some soybean research plots around southern and central Iowa have decent numbers feeding on unifoliates. Read more about early-season management of bean leaf beetle here.

 Soybean can compensate for early-season defoliation by bean leaf beetle. Photo by Erin Hodgson (17 May 2012 near Ames, IA).

Circular-shaped defoliation on leaves is an indicator of bean leaf beetle feeding, even if you don't see the beetles. Photo by Erin Hodgson (17 May 2012 near Ames, IA).

Check out these three new insect management articles!

Have you heard about a peer-reviewed extension publication called the Journal of Integrated Pest Management? It's an open-access journal (free for anyone to read and save files!). You can now access research-based management recommendations on all pests - not just insects and not just field crops. The Editors-in-Chief of JIPM are Marlin E. Rice of Pioneer Hi-Bred International (formerly with Iowa State University) and Kevin L. Steffey of Dow Agrosciences (formerly with the University of Illinois).

This new journal will offer a wide scope of peer-reviewed articles, including entomology, plant pathology and weeds. The intended readership for JIPM will be professionals who are engaged in any aspect of integrated pest management, especially those individuals working in crop protection, retailers, manufacturers and suppliers of pest management products, educators and pest control operators. The firs issue was released in October 2010.  and included articles about stalk borers and western bean cutworm. 

Three recently posted articles may be of particular interest to you. Click on the links to access pdf files:

1. Biology of the soybean aphid
2. Management of soybean aphid
3. Biology and management of bean leaf beetle and bean pod mottle virus

Alate (winged) soybean aphid and a few nymphs. Photo by Erin Hodgson