Mexican Bean Beetle
Epilachna varivestis
A bean-eating cousin of the ladybug that turns the family resemblance to its advantage. Coppery and spotted, the adults and their spiny yellow grubs feed on the undersides of bean leaves and skeletonize them to a lacy net, and a heavy infestation can defoliate a planting.
🔎 How to spot it
The adult is a rounded, convex beetle about a quarter inch, yellow to coppery-brown with sixteen black spots in three rows across the back, so it looks like an oversized ladybug. It is related to ladybugs, but unlike them it eats leaves, not pests. The larvae are bright yellow, oval, and covered in branched black-tipped spines, feeding in groups on the leaf undersides. Look for lacy, skeletonized leaves.
🥀 Damage it causes
Adults and larvae chew the tissue from the undersides of leaves and leave the upper surface and veins, giving the leaf a lacy, skeletonized, window-paned look. Heavy feeding can defoliate beans and cut the yield, and they will also scar pods. Snap, lima, cowpea, and soybean are all hosts.
🛡️ Prevent it
Plant quick-maturing bean varieties very early or in late summer to dodge the peak, and choose tolerant varieties where bean beetle is a regular problem. Cover young plants with row cover. Pull and destroy bean residue right after harvest by mowing or tilling, since the adults overwinter in garden trash nearby.
🧯 If it is already here
Handpick the adults and crush the yellow egg clusters and spiny larvae on the leaf undersides; in a garden, regular picking keeps them in check. For heavier pressure, the commercially available parasitic wasp Pediobius foveolatus is a proven biological control that lays its eggs in the larvae. Spinosad or insecticidal soap on the undersides helps in a pinch.
💡 Good to know
Do not mistake this pest for a beneficial ladybug: the giveaways are its bean-only diet, its coppery color with neat rows of spots, and especially its yellow, spiny larvae. The beetles overwinter as adults in leaf litter and field edges, so a clean fall garden is one of the best ways to lower the numbers the following year.
🌱 Plants it attacks
17 plants in the library can be attacked by this pest
For educational and informational purposes only. Pest control advice is general guidance drawn from university cooperative extension sources; always identify a pest positively and read and follow the label on any product before use, especially around food crops, children, and pets.