Southern Corn Rootworm in Soybean
Southern corn rootworm (Diabrotica undecimpunctata howardi), also known as spotted cucumber beetle, occurs east of the Rocky Mountains in the U.S. and in southeastern Canada. Southern corn rootworm is considered a minor pest in soybeans, and documented yield reductions are rare.
Crop Injury
Southern corn rootworm larvae may feed on soybean roots, and adults may feed on foliage, flowers, and pods.
Pest Description
Full grown larvae are 3/8 inches long and have a cream-colored body, a dark brown head, and a dark brown plate at the end of the abdomen. Adults are 1/4 inches long, yellow-green with a black head, black antennae, and 12 black spots on the back. Southern corn rootworm beetles resemble bean leaf beetles.
Southern corn rootworm beetle.
Russ Ottens, University of Georgia, Bugwood.org.
Southern corn rootworm beetle.
Daren Mueller, Iowa State University.
Scouting and Management
There are no established scouting or management thresholds for southern corn rootworm in soybeans. Special consideration should be made if southern corn rootworms are part of a complex of insects causing defoliation. If defoliation is present, randomly select enough scouting locations to represent the field—larger fields may need additional sites to represent the whole field. Use the Crop Protection Network’s Insect Defoliation Tool to help you correctly assess the level of defoliation. The standard soybean defoliation treatment thresholds are 30% in the vegetative stages and 20% in the reproductive stages. Contact your local or state extension specialist for information on the most current scouting and management options.
Developed and reviewed by Carol Pilcher, Iowa State University and Robert Wright, University of Nebraska-Lincoln, with support from the United Soybean Board.
Southern corn rootworm beetle. Russ Ottens, University of Georgia, Bugwood.org.
Southern corn rootworm beetle. Daren Mueller, Iowa State University.
Gallery images courtesy of Russ Ottens, University of Georgia, Bugwood.org and Daren Mueller, Iowa State University.
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