Mexican Bean Beetles

Mexican bean beetles are a very destructive type of lady beetle. Unlike beneficial lady beetles that feed on aphids and other pests, these “ladybugs" feed on plants. Mexican bean beetles target plants in the legume family, such as lima beans, snap beans, cowpeas, and soybeans. Both mature beetles and their larvae cause plant damage by feeding on leaves, flowers, stems and bean pods. Several generations can occur in a season.

Identification: Oval-shaped adult Mexican bean beetles are easy to see and identify. About 1/3 inch in length, they range in color from orange to copper. Across their backs, 16 black spots occur in three rows, 6-6-4, from head to tail. Their oval-shaped, soft-bodied, yellow larvae are covered in black, fuzzy spines. Eggs, found in large clusters on the undersides of leaves, look like tiny, yellow footballs attached by their tips.

Signs/Damage: Mexican bean beetle leaf damage focuses on the lower surface of tender tissue between leaf veins. Damage shows through on upper leaf surfaces as transparent “window panes" and a skeleton of leaf veins. Skeletonized leaves curl, die and drop.

Control: Effective control of Mexican bean beetles starts as the pests emerge in spring. GardenTech^® brand offers several products to kill Mexican bean beetles by contact and keep protecting for up to three months+. These products can be used to treat dried beans up to 21 days before harvest or succulent beans up to one day before you pick and eat*:

• Sevin^® Insect Killer Concentrate provides a simple, economical option for treating bean crops from bush beans to pole beans. Use with a pump-style sprayer, and cover all plant surfaces thoroughly. Pay special attention to the undersides of leaves and leaf-covered stems where Mexican bean beetles may hide and feed.
• Sevin^® Insect Killer Ready to Spray attaches to a common garden hose to measure and mix automatically as you spray. When spraying large areas, start at the farthest point and work your way backward. This keeps you and your hose dry and removed from freshly sprayed beans.
• Sevin^® Insect Killer Ready to Use simplifies treating smaller garden areas or spot treating exposed Mexican bean beetles. The adjustable nozzle lets you control the width of the product stream. Spray to contact visible pests and cover both the upper and lower surfaces of target plants thoroughly.

Tip: Mexican bean beetles overwinter in garden debris and leaf litter. After your bean harvest, remove and discard all plant debris to minimize the number of beetles that emerge come spring

*Always read product labels and follow the instructions carefully, including guidelines for pre-harvest intervals on succulent or dried edible crops .

+These products provide up to 3 month control on all listed insects except ticks.

GardenTech is a registered trademark of Gulfstream Home and Garden, Inc.

Sevin is a registered trademark of Tessenderlo Kerley, Inc.

PHOTO CREDIT: 

• "Mexican bean beetle (Epilachna varivestis)" by Whitney Cranshaw at Colorado State University (Bugwood.org) licensed under CC BY 3.0 US
• "Mexican bean beetle (Epilachna varivestis)" by Whitney Cranshaw at Colorado State University (Bugwood.org) licensed under CC BY 3.0 US
• "Mexican bean beetle (Epilachna varivestis)" by Whitney Cranshaw at Colorado State University (Bugwood.org) licensed under CC BY 3.0 US
• "Mexican bean beetle (Epilachna varivestis)" by Clemson University - USDA Cooperative Extension Slide Series (Bugwood.org) licensed under CC BY 3.0 US