Guess the Pest! | Weekly Crop Update

Bill Cissel, Extension Agent – Integrated Pest Management; bcissel@udel.edu

Congratulations to Mona Steele for identifying the insect damage in this past week’s Guess the Pest and for being selected to be entered into the end of season raffle for $100 not once but five times. Everyone else who guessed correctly will also have their name entered into the raffle. Mona will also receive a FREE copy of A Farmer’s Guide to Corn Diseases. Click on the Guess the Pest logo below to participate in this week’s Guess the Pest! For Guess the Pest # 9, we will also be giving away A Farmer’s Guide To Corn Diseases ($29.95 value) to one lucky participant.

http://www.plantmanagementnetwork.org/book/cornfarmersguide/

Guess the Pest Week #9
Answer is…Bean Leaf Beetle

Bean leaf beetles attack soybeans throughout the entire growing season. Their color varies and can be red, tan, green, or orange. The number of black spots on their wing covers also varies from several to none (four spots is common). The one distinct characteristic that they all have regardless of color or number of spots is the black triangle located behind the thorax.

Bean leaf beetles will feed on cotyledon leaves as the plants emerge and can reduce stands. As the soybeans continue to develop, they will also damage unifoliate and trifoliate leaves. The threshold for bean leaf beetles is 2 per ft of row and 25% stand reduction from emergence to 2 trifoliate. After 2 trifoliate, the threshold is 2-3 per plant and 30% defoliation. As the plants mature and the leaves begin to senesce, they will feed on the soybean pods, removing the green tissue and leaving a thin white membrane over the seed. This damage may result in “moldy beans” depending on the weather conditions prior to harvest.