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Past Articles Library | Organic Pest Control | Mexican Bean Beetle



 

MEXICAN BEAN BEETLE CONTROL
Epilachna varivestis

Mexican bean beetles are often mistaken for lady bugs, so the one key thing to look for is the distinctive fat, yellow larva.

 
 

DESCRIPTION

Adults are oval, yellowish brown to copper-colored beetles, 1/4 inch (6 mm) long, with 16 black spots arranged in three rows across their wing covers. They look like lady beetles (which are beneficial insects and should not be killed) so look for the distinctive larvae for proper identification. Larvae are fat, yellowish to orange grubs up to 1/3 inch (8 mm) long, with no legs, and with six rows of long, branching spines sticking out from their segments. Eggs are yellow ovals.

 
 

LIFE CYCLE

Adults overwinter in garden debris and leaf litter in nearby fields. Some emerge to feed by the time the first bean leaves are up, while others come out over a period of several months. In the spring, the beetles feed for a couple of weeks, then females lay eggs on end in clusters of 40 to 60, on the undersides of bean leaves. Eggs hatch in 5 to 14 days, and larvae feed for 2 to 5 weeks. They pupate in a case attached to the underside of a leaf, and adults emerge about a week later. Upon emergence, new adults are solid yellow; they soon darken and the spots become visible. One to four generations per year. In late summer, large numbers of beetles disperse from fields.

 

 

PLANTS MOST AFFECTED

Cowpea, lima bean, snap bean, green bean, string bean, bush and pole beans, and soybean.

 

 

DAMAGE

Both larvae and adults feed from the underside on leaf tissue between the veins; they skeletonize the leaves, leaving behind a characteristic lacy appearance. In severe attacks, production of pods may be reduced, and completely defoliated plants may be killed. The greatest damage happens in July and August. Bean beetles are most abundant in weedless fields.

 
 

MEXICAN BEAN BETTLE CONTROL

Prevention:

1. Plant resistant cultivars such as 'Wade' and 'Logan' snap beans and 'Black Valentine' lima bean.

2. Plant early season bush beans to avoid main beetle generations.

3. Cover seedlings and plants with Floating Row Covers until the plants are well grown and mature. Make sure the floating row cover edges are buried in the soil.
More Information About Floating Row Covers

4. Leave a few flowering weeds between rows to attract native predators and parasites, or interplant with flowers such as Queen Anne's lace or yarrow, and herbs such as dill to encourage beneficial insects such as spined soldier bugs (Podisus maculiventris) and parasitic wasp Pediobius foveolatus.

5. Remove any debris and dig under crop residues as soon as plants are harvested to remove overwintering sites.

Control:

1. Plant soybeans as a trap crop; destroy the plants when they are infested with beetle larvae.

2. In small bean patches, handpick larvae and adults and crush egg masses daily. If done with regularity, this will reduce damage from the second generation considerably

3. Release spined soldier bugs (Podisus maculiventris) to control early generation.

4. Release the parasitic wasp Pediobius foveolatus when weather warms up to control second generation.

5. Spray Bulls-Eye Bioinsecticide for control of foliage feeding pests on leafy vegetables, beans and peas.
More Information about Bulls-Eye Bioinsecticide

6. Spray weekly with Liquid Rotenone / Pyrethrin Spray making sure the undersides of the leaves are thoroughly covered.
More Information Rotenone/Pyrethrin Spray








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Gardening-tip:



When to Harvest Squash

Winter squash is ready for harvest after the rind hardens and surface color dulls.

The vines will have dried and the skins are hard and can't be scratched with a fingernail.

Make sure you get them in before the first hard frost.


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