Problem Identifier Unit Screen//v.w/ RR Template

Problem Identifier Unit Screen//v.w/ RR Template Bean Leaf Beetle

Problem
Holes are chewed in the leaves. Yellow to red beetles with black spots and a black band around the outer edge of the body are feeding on the undersides of the leaves. The plant may later turn yellow and wilt. If you pull the plant up you may see slender white grubs up to 1/3 inch long feeding on the roots and stem.

Analysis
(Cerotoma trifurcata)

This widely distributed insect attacks all beans, as well as peas. Adult beetles feed on the undersides of leaves, blossoms, and pods throughout the growing season. Grubs feed on the roots and stems below the soil line. Females lay clusters of orange eggs on the soil at the base of plants. The grubs that hatch from these eggs attack the plant below the soil, feeding on the roots and sometimes girdling the stem at the soil level. This feeding can kill the plant. Both adults and grubs cause serious damage to young plants. There are 1 to 3 generations per year.

Solution
Apply an insecticide containing carbaryl or diazinon at the first sign of damage. Be sure to spray the undersides of the leaves where the beetles feed. Repeat at intervals of 7 to 10 days whenever damage occurs. Clean all debris from the garden at the end of the season to eliminate overwintering spots for adults.

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