Cereal leaf beetle has plagued wheat and other small grain farmers since the early 1960s.

As with most non-native insects, the beetle’s biology and ecology are an enigma, and it thrives in the absence of aggressive predators.

Although timed spraying controls the beetle if populations are low, it does little to control high beetle populations or prevent the losses sustained from the larvae’s incessant feeding.

To make cereal leaf beetle control less of a gamble, researchers at North Carolina State University and Virginia Polytechnic Institute and State University have discovered a way to help growers use scouting and thresholds more effectively.

Native to Europe and Asia, cereal leaf beetle was first discovered in southern Michigan in the early 1960s and has become one of the primary pests of small grains.

The most destructive life stage of the beetle is the larvae, which skeletonize the leaf, decreasing the plants ability to photosynthesize and giving the field a frosted appearance. Losses can reach 40 percent.

Federal agencies, researchers and growers have tried numerous efforts to control the pest.

After the beetle’s arrival, Michigan and Indiana were placed under quarantine, and small grains in other states had to be treated before transport. When those efforts failed, large-scale spray programs began, but these failed to stop the spread of the beetle as well. By 1970, all quarantine and eradication efforts had ended, and cereal leaf beetle was well established in the U.S.
Researchers turned to IPM tactics such as host plant resistance and biological control, but these tactics gained little traction with wheat growers.

Resistant wheat plants did not produce the yield of the more susceptible varieties, and imported parasitoids worked well in some areas but did not thrive in others. In addition, continued use of regular calendar sprays further reduced the predator population.

Growers had good reasons for a prophylactic spray program; many would mix insecticide with a nitrogen application or a fungicide that they were using anyway.

To many growers, the tank-mixes made economical sense, and many argued they didn’t suffer a yield loss from cereal leaf beetle because they had protected their field.

In addition, growers who wanted to scout had to do so between March and June, an extraordinarily long scouting season, and many of them scouted the fields on their tractor, flattening the wheat tillers and reducing yield.