The Mexican bean beetle (''Epilachna varivestis'') is a species of

lady beetle Coccinellidae () is a widespread family of small beetles ranging in size from . They are commonly known as ladybugs in North America and ladybirds in Great Britain. Some entomologists prefer the names ladybird beetles or lady beetles as they ...

that can be an agricultural pest. It is one of the few North American lady beetles that feed on plants rather than other insects. It is found throughout Mexico and the eastern United States, and is abundant in the wetter and more heavily irrigated areas west of the

Rocky Mountains The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico ...

. It does not tolerate extremely dry areas.

Identification

Adults are similar in appearance to other lady beetles, oval-shaped, approximately 6 to 7 millimeters long and bearing eight black spots on each

elytron An elytron (; ; , ) is a modified, hardened forewing of beetles (Coleoptera), though a few of the true bugs (Hemiptera) such as the family Schizopteridae are extremely similar; in true bugs, the forewings are called hemelytra (sometimes alterna ...

. Adult color is quite variable, ranging from bright red to rusty brown to golden yellow. The eggs are yellow, about 1.3 millimeters in length, and glued in clusters of up to 75 on the undersides of leaves. The larvae are usually yellow, spiny, and pill-shaped. Each is approximately 1.6 millimeters in length when first emerged, and grows to about centimeter length before

pupation A pupa ( la, pupa, "doll"; plural: ''pupae'') is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in thei ...

Distribution

Mexican bean beetle is present in the United States and found in most eastern states of the United States and Mexico. It can be found as far south as Guatemala and north into southern Canada or

New England New England is a region comprising six states in the Northeastern United States: Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont. It is bordered by the state of New York to the west and by the Canadian provinces ...

. The Mexican bean beetle is likely native to the southern plateau region of Mexico. Presence depends on the factors such as precipitation. It does not cause significant crop damage in Guatemala and Mexico, but can be abundant in isolated areas of the western United States.

Feeding

Both adults and larvae feed on leaf, flower, or pod tissue on

bean A bean is the seed of several plants in the family Fabaceae, which are used as vegetables for human or animal food. They can be cooked in many different ways, including boiling, frying, and baking, and are used in many traditional dishes th ...

s and other

legume A legume () is a plant in the family Fabaceae (or Leguminosae), or the fruit or seed of such a plant. When used as a dry grain, the seed is also called a pulse. Legumes are grown agriculturally, primarily for human consumption, for livestock for ...

s. It can be found on a great variety of bean plants, including common bean, thicket bean, lima bean, cowpea, adzuki,

mung bean The mung bean (''Vigna radiata''), alternatively known as the green gram, maash ( fa, ماش٫ )٫ mūng (), monggo, or munggo (Philippines), is a plant species in the Fabaceae, legume family.Brief Introduction of Mung Bean. Vigna Radiata ...

, and soybean. It will also attack other legumes such as

alfalfa Alfalfa () (''Medicago sativa''), also called lucerne, is a perennial flowering plant in the legume family Fabaceae. It is cultivated as an important forage crop in many countries around the world. It is used for grazing, hay, and silage, as ...

and various

clovers Clover or trefoil are common names for plants of the genus ''Trifolium'' (from Latin ''tres'' 'three' + ''folium'' 'leaf'), consisting of about 300 species of flowering plants in the legume or pea family Fabaceae originating in Europe. The genus h ...

. Adult beetles may eat the fruits and flowers of the plants, but generally prefer the leaves. Feeding damage is most prevalent from skeletonization where beetles feed on the

parenchyma Parenchyma () is the bulk of functional substance in an animal organ or structure such as a tumour. In zoology it is the name for the tissue that fills the interior of flatworms. Etymology The term ''parenchyma'' is New Latin from the word � ...

of the leaves from the underside, leaving the upper epidermis intact. This gives the leaf a lacy appearance. The larvae generally do much more damage than the adults.

Life cycle

Adults emerge from dormancy in late spring, and each female lays several hundred eggs in clusters of 50 to 75 on bean plant leaves. The larvae are voracious feeders, and can inflict heavy damage on a field of bean plants during an infestation. After a few weeks of feeding, the larvae pupate in groups under the leaves. They winter as adults, and often travel long distances to find new fields.

Control

The parasitoid wasp ''

Pediobius foveolatus ''Pediobius foveolatus'' ( Crawford) (Fig. 1 and 3), is a tiny exotic parasitoid wasp that is used for biological control of Mexican bean beetle, ''Epilachna varivestis'' (Fig. 2), an important insect pest of snap beans, lima beans, and someti ...

'' can be used as augmentative biological control against the Mexican bean beetle. Systemic insecticides are commonly used at planting where Mexican bean beetle is a frequent pest. Some of these insecticides do not persist in the plant long enough to protect the plant from early generations. Delayed planting or a trap crop can reduce the likelihood of significant populations.

Identification

Distribution

Feeding

Life cycle

Control

References

Further reading