''Cerotoma trifurcata'' (also known as the bean leaf beetle) is a species of

beetle Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describ ...

in the

Chrysomelidae The insects of the beetle family Chrysomelidae are commonly known as leaf beetles, and include over 37,000 (and probably at least 50,000) species in more than 2,500 genera, making up one of the largest and most commonly encountered of all beetle ...

family that can be found in the Eastern and West United States.

Description

Adult An adult is a human or other animal that has reached full growth. In human context, the term ''adult'' has meanings associated with social and legal concepts. In contrast to a " minor", a legal adult is a person who has attained the age of major ...

beetles are in length, and have a punctated elytron at their posterior region. Morphs can have colors ranging from light gray to shades of yellow, brown, orange, or red. The elytra has a black triangle in the middle behind the thorax and typically has six additional black spots with a black band around the edges, though non-spotted morphs also occur. The head is always black. , Beanleafbeetlered.jpg, red morph Cerotoma_trifurcata-brown.jpg, brown morph Cerotoma_trifurcata-spotless.jpg, spotless morph

Habitat and ecology

The beetle feeds mostly on vegetables that are in the

cotyledon A cotyledon (; ; ; , gen. (), ) is a significant part of the embryo within the seed of a plant, and is defined as "the embryonic leaf in seed-bearing plants, one or more of which are the first to appear from a germinating seed." The numb ...

-stage, such as

cucumber Cucumber (''Cucumis sativus'') is a widely-cultivated Vine#Horticultural climbing plants, creeping vine plant in the Cucurbitaceae family that bears usually cylindrical Fruit, fruits, which are used as culinary vegetables.

s, cucurbits,

pumpkin A pumpkin is a vernacular term for mature winter squash of species and varieties in the genus ''Cucurbita'' that has culinary and cultural significance but no agreed upon botanical or scientific meaning. The term ''pumpkin'' is sometimes use ...

, and squash. It also can be a pest of

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 f ...

s such as soybean. In early spring, adult beetles emerge to feed on legumes, such as alfalfa, before crops such as soybeans and green beans are available. Multiple generations occur per year depending on growing season length with one generation in northern climates, such as

Ontario Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geographic eastern half of Canada, but it has historically and politically been considered to be part of Central Canada. Located in Central Ca ...

, one to two generations in the

Upper Midwest The Upper Midwest is a region in the northern portion of the U.S. Census Bureau's Midwestern United States. It is largely a sub-region of the Midwest. Although the exact boundaries are not uniformly agreed-upon, the region is defined as referring ...

US, and three generations in the southeastern US. Bean leaf beetle mostly overwinters in woodlot

leaf litter Plant litter (also leaf litter, tree litter, soil litter, litterfall or duff) is dead plant material (such as leaves, bark, needles, twigs, and cladodes) that have fallen to the ground. This detritus or dead organic material and its constituent ...

, but can also be found in crop fields under soybean debris. Significant mortality can occur below

Feeding

Larvae feed in the soil on plant roots, while adults consume vegetative tissue on host plants. Bean leaf beetle can also transmit bean pod mottle virus to beans through feeding. Feeding can significantly affect crop yield in some cases, although such damage is highly dependent on beetle densities in a field. Insecticides, such as pyrethroids, and delayed planting dates have been used to manage bean leaf beetle populations, but conditions when such measures are effective vary. Insecticidal seed treatments alone do not increase yield in areas prone to bean leaf beetle feeding or virus transmission.

References

{{Taxonbar, from=Q2193436 Galerucinae Beetles described in 1771 Insects of the United States Taxa named by Johann Reinhold Forster