Bean leaf bugs are beetles that feed on a variety of bean plants, causing cosmetic damage and health problems that often become severe. Bean leaf bugs are known for their tendency toward carrying infectious diseases, however, transmission is a concern for commercial growth but not cause for alarm in the home garden. Familiarize yourself with what to watch for in your bean garden as well as what to do should you spot a beetle problem.
When growing beans in the home garden, proper care often results in vigorous plants that are capable of resisting or fighting off pest infestations. Grow beans in locations that provide full sunlight for optimal growth, according to the Purdue University Cooperative Extension. Rotate your crops annually to avoid problems and stressed plants that are more vulnerable to bean leaf bugs. Plant bean in loose, well-drained soil.
Bean leaf bugs, also referred to as bean leaf beetles (Cerotoma tifurcata), are pests to a variety of bean plants including soybeans, clover, snap beans and other dry beans, according to the University of Minnesota Extension. Bean leaf bugs display winged, ovular, yellow-green or red bodies with black spots and borders. All bean leaf beetles display a black triangle on the upper back. Adult bean leaf bugs measure approximately 1/4 to 1/5 inch in length, according to the Clemson University Extension. These bugs overwinter in soil and appear during the warmer months of May through June.
In their larval stage, bean leaf bugs feed on the roots of bean plants but usually do not cause significant harm. Adults also feed on bean plants though they target new leaf growth. As they feed, adult bean leaf bugs create holes up to 1/8 inch in diameter in leaves. Look for leaf drop, diminished health, a drop in bean production as well as the death of seedlings that occurs in severe cases, according to the University of Minnesota.
For natural control of leaf bean bugs on your bean plants, fill a bucket with a solution of water and soap. Either pluck the beetles from plants by hand or gently tap the plants with the bucket located as as a catch below. No matter the method of removal you choose, the goal is for the beetles to fall into the soapy water to their death. This is a successful method in small home bean gardens, according to the University of Minnesota Extension.
For chemical control, particularly in larger bean gardens, the use of chemical insecticides offers effective management. Apply insecticides only if you have identified a substantial population of bean leaf bugs in your bean garden. Use a chemical spray with the active ingredient esfenvalerate or carbaryl, according to the University of Minnesota Extension. When in need of assistance or advice, contact a licensed professional or your local county extension agent.