Bean Leaf Beetle in Soybeans
Bean Leaf Beetle
Description
Adult bean leaf beetles are small, approximately 1/8 to 1/4 inch long. Their bodies are somewhat convex and the
Bean Leaf Beetle
University of Kentucky Dept. Entomology
beetle is longer than it is wide. Color can vary greatly, ranging from light brown to dark red; spots and/or stripes may be present or absent. A key factor you can use in identification of the adult bean leaf beetle is that all bean leaf beetles have a backwards pointing black triangle on the wing covers behind the head.
The larva is almost identical to that of the corn rootworm. Bean leaf beetle larvae are white and segmented, with a brown head and a brown hardened area at the posterior end of the body. Larvae may be found feeding on soybean roots and nodules.
Damage
Damage to soybeans is usually caused by the adult bean leaf beetle. Adults feed on cotyledons and leaves, making distinct round holes. They sometimes feed on pod surfaces but seldom eat through to the seeds. Damage to roots and nodules by larvae has not been shown to significantly reduce yields.
IPM Techniques and Scouting
Scout seedlings (cotyledon stage) by looking for stand reduction and heavy leaf feeding as you walk the field. If damage is found, try to establish that bean leaf beetles are present. If soybeans are in the seedling stage, a control should be considered if 30% stand loss due to cotyledon feeding or 30% defoliation has occurred.
Mid-season plants may be scouted using the shake cloth procedure or the sweep net procedure. Using a fifteen inch sweep net, twenty sweep samples should be taken at each location. For the ground cloth procedure, place a two foot wide strip of cloth on the ground between rows and bend the plants over the cloth and shake them vigorously. This provides a four foot sample. Sampling for pod damage is done by checking five plants at each sample site for damaged pods. The number of sites you need to examine in a field is based on the size of the field.
Economic Thresholds for Bean Leaf Beetles in Soybeans
Bean Leaf Beetle Activity
Please note: These dates are approximations only. This calendar was constructed using data from Kentucky, USA. These dates may not apply in your area. You may wish to contact your county extension agent or agricultural consultant for information tailored to your locality.
References and Additional Information
- IPM -3 Kentucky IPM Manual for Soybeans
- Illinois Field Crop Scouting Manual
- Purdue University - Field Crops Pest Management Manual
- Handbook of Soybean Insect Pests by Leon G. Higley and David J. Boethel, Entomological Society of America
