Integrated Crop Management

Bean leaf beetles and others: correctly identifying the pest

Walk through an alfalfa field this time of year and you are likely to find numerous insects at your feet. Many are beetles. With the economic importance of bean leaf beetles rising, it is vital that this beetle be correctly identified from other beetles, many of which can later be found in soybean as well.

To correctly identify the bean leaf beetle, look for a black triangle behind its "neck." Many bean leaf beetles also have four square or rectangular marks on their wing "covers" and are dark yellow. However, do not be misled! Some bean leaf beetles are red or do not have markings on their wing covers. To aid in identification, we present photographs of beetles that may be found in alfalfa this spring.

Bean leaf beetle (red phase and yellow phase. Note black triangle behind its neck. This character will distinguish this beetle from all others in this region.

Twelvespotted lady beetle with a characteristic pink coloration.

Fifteenspotted lady beetle. Note the characteristic white markings behindthe head (much more than the sevenspotted lady beetle).

Flea beetle, though not an alfalfa pest, may be found in weedy alfalfa fields.

Convergent lady beetle. Note the characteristic white lines behind the head.

Sevenspotted lady beetle. Note the characteristic white markings behind the head.

Asian multicolored lady beetle has a highly variable spot pattern and characteristic black markings behind the head.

Southern corn rootworm (or spotted cucumber beetle). Its rows of black spots on a lime green-to-yellow body are reliable characteristics.

Alfalfa weevil, an economically important alfalfa pest, has a dark stripe down the middle of its body.

This article originally appeared on page 72 of the IC-490 (9) -- May 19, 2003 issue.

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