Fact Sheets And Publications
Non-chemical pest control options for managing insect pests on beans
Reviewed March 2025 | Written by:听Dr. Judy Hough-Goldstein
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July and August in the vegetable garden typically bring bountiful harvests of colorful vegetables. These are also the months when insect pests can really make their presence known, with plant and fruit damage becoming increasingly noticeable.听
Mexican bean beetles听
Mexican bean beetles are plant-feeders in the same family as ladybird beetles (ladybugs)鈥攎ost of which are beneficial predators.
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Type of damage
Both adults and larvae feed on foliage, skeletonizing the leaves.
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Life cycle
Adults overwinter and emerge with warm weather. Adults feed on tender young bean plants for approximately 12 days, then lay eggs (in batches of 40 to 70) on the undersides of leaves; distinctive spiny yellow larvae feed for 2 to 5 weeks, then pupate on leaves. There is only one generation per year, but egg-laying continues all summer.
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Life cycle听with suggested control methods:
- Adults overwinter and emerge with warm weather. Adults feed on tender young bean plants for approximately 12 days, then lay eggs (in batches of about 40 鈥 70) on the undersides of leaves; distinctive spiny yellow larvae feed for 2 to 5 weeks, then pupate on leaves. There is only one generation per year, but egg-laying continues all summer.
- Like most beetles, adults 鈥減lay dead鈥 (withdraw appendages and drop to the ground) when disturbed.听Place open containers with soapy water under beetles, and catch/drown them as they drop. Try to kill the adults as they appear on plants before they lay eggs.
- Crush any eggs and larvae.听
- Row covers听can be used over bean plants to exclude adults and can be kept in place all season (beans do not require insect pollinators)
- For heavily infested plants, practice 鈥destructive harvest鈥 鈥 pull plants up by the roots, harvest any viable beans, then put the remaining plants (with beetle eggs, larvae, and adults) in听black plastic bags. Seal and leave in the sun for several days to kill the pests.听
This factsheet was created for 91原创 Cooperative Extension and the Delaware Master Gardener Program by听Dr. Judy Hough-Goldstein.
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