of Rhode Island GreenShare Factsheets
Epilachna varivestis Mulsant
Mexican bean beetle adults and larvae feed on the undersides
of leaves of several plants, including garden beans, cowpeas
and soybeans, leaving the leaves skeletonized with a lace-like
appearance. Although feeding occurs mainly on the leaves, young
pods and even the stems may be attacked and destroyed. Severely
affected leaves often dry up and drop off the plant, reducing
photosynthetic efficiency and yield. Serious infestations may
result in the death of young plants.
The Mexican bean beetle is one of the few harmful members
of the lady beetle family. The copper-colored adults resemble
large lady beetles. They are about 6 mm (1/4 inch) long and
5 mm (1/5 inch) wide, with 8 small black spots on each wing.
Immature larvae are yellow and are covered with large spines.
Yellow eggs 1 mm (1/20 inch) in length are laid in groups of
40-60 on the lower leaf surfaces.
Adult beetles overwinter on the ground in leaf litter
and other sheltered areas in fence rows and field edges. Adults
begin emerging from these protected areas when beans begin
sprouting and continue to emerge for up to two months. The
adults feed for approximately two weeks before depositing their
eggs on the underside of leaves. Females may deposit an egg-mass
every two to three days. Eggs hatch in 5-24 days and larvae
feed for two to five weeks before pupation. The greatest amount
of injury occurs in July and August, and the adults begin to
disappear in late summer.
- Plant early and fast-maturing varieties to reduce damage
and crop loss.
- Plant bush beans instead of pole beans and pick pods
as soon as they mature.
- Plants should be plowed under as soon as the crop is
harvested to eliminate late-developing beetles and to prevent
a within-field overwintering site.
- "Floating-row" covers such as
Remay work well as protective barriers.
- If necessary, plants may be protected by insecticides
applied according to label directions.
By Richard A. Casagrande
and David B. Wallace, 1999
are poisonous! Read and follow all safety precautions on labels.
Handle carefully and store in original containers out of reach
of children, pets or livestock. Dispose of empty containers
immediately, in a safe manner and place. Pesticides should never
be stored with foods or in areas where people eat.
When trade names are used for identification, no product endorsement
is implied, nor is discrimination intended against similar materials.
Be sure that the pesticide you intend to use is registered for
the state of use.
The user of this information assumes all risk for personal injury
or property damage.
information, call the URI CE Gardening and Food Safety Hotline
at 1-800-448-1011 or (401)874-2929 from outside Rhode Island;
Monday-Thursday between 9 am and 2 pm.
of Rhode Island Cooperative Extension provides equal program