Epilachna varivestis
Encyclopedia
The Mexican bean beetle, Epilachna varivestis, is a species of lady beetle
which is a notorious agricultural pest. It is one of the few 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
. It does not tolerate extremely dry areas.
It is similar in appearance to other lady beetles, oval-shaped and bearing eight black spots on each elytron
. Its overall color is quite variable, ranging from bright red to rusty brown to golden yellow. It is 6 or 7 millimeters long. 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 1.5 millimeters in length when first emerged, and grows up to one centimeter long before pupation. The larva attaches its anal segment to the underside of a leaf and hangs there to pupa
te.
The Mexican bean beetle feeds on bean
s and other legumes. It can be found on a great variety of bean plants, including common bean varieties (Phaseolus vulgaris
), lima bean (Phaseolus lunatus
), cowpea and azuki and mung beans (Vigna
spp.), and soybean (Glycine max
). It will also attack other legumes such as alfalfa (Medicago sativa) and various clovers (Trifolium spp.). Adult beetles may eat the fruits and flowers of the plants, but generally prefer the leaves. They eat the tender parenchyma
of the leaves from the underside, leaving the upper epidermis intact. This gives the leaf a lacy, "skeletonized" appearance. The larvae also eat the leaves, and they do much more damage than the adults.
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 gorging on plants the larvae pupate in groups under the leaves. They winter as adults, and often travel long distances to find new fields.
Several types of insects show promise as biological pest control
agents against the Mexican bean beetle, but insecticides are still routinely used in areas of high economic impact.
Coccinellidae
Coccinellidae is a family of beetles, known variously as ladybirds , or ladybugs . Scientists increasingly prefer the names ladybird beetles or lady beetles as these insects are not true bugs...
which is a notorious agricultural pest. It is one of the few 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
Rocky Mountains
The Rocky Mountains are a major mountain range in western North America. The Rocky Mountains stretch more than from the northernmost part of British Columbia, in western Canada, to New Mexico, in the southwestern United States...
. It does not tolerate extremely dry areas.
It is similar in appearance to other lady beetles, oval-shaped and bearing eight black spots on each elytron
Elytron
An elytron is a modified, hardened forewing of certain insect orders, notably beetles and a few of the true bugs ; in most true bugs, the forewings are instead called hemelytra, as only the basal half is thickened while the apex is membranous...
. Its overall color is quite variable, ranging from bright red to rusty brown to golden yellow. It is 6 or 7 millimeters long. 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 1.5 millimeters in length when first emerged, and grows up to one centimeter long before pupation. The larva attaches its anal segment to the underside of a leaf and hangs there to pupa
Pupa
A pupa is the life stage of some insects undergoing transformation. The pupal stage is found only in holometabolous insects, those that undergo a complete metamorphosis, going through four life stages; embryo, larva, pupa and imago...
te.
The Mexican bean beetle feeds on bean
Bean
Bean is a common name for large plant seeds of several genera of the family Fabaceae used for human food or animal feed....
s and other legumes. It can be found on a great variety of bean plants, including common bean varieties (Phaseolus vulgaris
Common bean
Phaseolus vulgaris, the common bean, is an herbaceous annual plant domesticated independently in ancient Mesoamerica and the Andes, and now grown worldwide for its edible bean, popular both dry and as a green bean. The leaf is occasionally used as a leaf vegetable, and the straw is used for fodder...
), lima bean (Phaseolus lunatus
Lima bean
Phaseolus lunatus is a legume. It is grown for its seed, which is eaten as a vegetable. It is commonly known as the lima bean or butter bean.-Origin and uses:...
), cowpea and azuki and mung beans (Vigna
Vigna
The genus Vigna is in the plant family Fabaceae. The genus is named after Domenico Vigna, an Italian botanist of the 17th century. They include some well-known and other less well-known beans formerly — and sometimes still, especially in non-scholarly sources — included in the genus Phaseolus...
spp.), and soybean (Glycine max
Soybean
The soybean or soya bean is a species of legume native to East Asia, widely grown for its edible bean which has numerous uses...
). It will also attack other legumes such as alfalfa (Medicago sativa) and various clovers (Trifolium spp.). Adult beetles may eat the fruits and flowers of the plants, but generally prefer the leaves. They eat the tender parenchyma
Ground tissue
The types of ground tissue found in plants develop from ground tissue meristem and consists of three simple tissues:* Parenchyma...
of the leaves from the underside, leaving the upper epidermis intact. This gives the leaf a lacy, "skeletonized" appearance. The larvae also eat the leaves, and they do much more damage than the adults.
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 gorging on plants the larvae pupate in groups under the leaves. They winter as adults, and often travel long distances to find new fields.
Several types of insects show promise as biological pest control
Biological pest control
Biological control of pests in agriculture is a method of controlling pests that relies on predation, parasitism, herbivory, or other natural mechanisms...
agents against the Mexican bean beetle, but insecticides are still routinely used in areas of high economic impact.