Bean Leaf Beetle – Identification and Destruction

by Austin Pelyak, Sustainable Plant Systems major

Bean Leaf Beetle (BLB) is a major pest in soybean production. It can be a very illusive insect for many producers because unlike many insects that attack soybeans this beetle attacks soybeans twice a year. First sighting of the BLB can be early in the season, usually in first planted fields in the county or local area. The beetles feed on the new foliage causing an abundance of defoliation in the newer succulent tissues. The beetles seem to be more prevalent where more crop residue is present on the soil surface.  Early season damage is usually minimal so a spray is usually not required.

After several weeks of feasting on the new growth, the BLB mates, lays its eggs into the soil and carries out the rest of its life until eaten by a predator or death of natural causes. The eggs remain in the soil, hatch, and larva emerge. By mid-growing season, the larva of the BLB then begins to feed on the roots and nodules produced by the soybean plant. Feeding on the roots and nodules can invite unwanted pathogens or bacteria into the plant that can harm overall plant health. These larva feed and then resort to the pupa form to complete its final stage before adulthood and sexual maturity.

Once emerged from the soil, the BLB begins to feast on everything edible. Leaves, buds, and new pods are on the menu for this pest. Chewing of the pods can cause major yield loss and more pathogens to enter. This can reduce overall grain quality and takes cash out of the farmer’s pocket. BLB can also transmit Bean Pod Mottle virus which can affect growers who save seed or growers who are producing soybean seed.

This blog post was an assignment for Societal Issues: Pesticides, Alternatives and the Environment (PLNTPTH 4597). The views expressed are those of the author and do not necessarily reflect the views of the class, Department of Plant Pathology or the instructor.

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