Bean Leaf Beetle Damage
o your bean leaves look lacelike? Are copper colored beetles present? Could be epilachna varivestis. Find out what they are and what to do.
What is it?
Beetles of the family, epilachna varivestis feed on lima, pole, and bush beans giving plant tissues a lacelike appearance and occasionally killing off entire plants.
What does it look like?
Beetles are approximately 1/4 inch long, copper colored and have 16 black spots on their backs. Grubs are about 1/3 inch long with black tipped spines. Tissue between leaf veins is eaten on the plants and leaves eventually dry up and die off.
How does it manifest?
Females lay eggs on the undersides of leaves. Eggs are yellow. Larvae hatch in early to mid-summer turning green then yellow. Both adults and larvae feed on leaf tissue. 1 to 4 generations of damage may occur each year, with all levels of maturity in the beetles being represented at any given time.
What can you do about it?
When you first notice damage, apply insecticide containing diazinon or carbaryl, making sure you coat undersides of leaves. You may need to reapply later in the season if damage continues, but early insecticide application can stave off damage from successive generations of larvae which tend to be harder to kill than adults. After you harvest from the plants, destroy and remove all plant debris from the area to prevent an overwintering environment for adult beetles.