Using Like Plants as Trap Crops to Control the Harlequin Bug

BLACKSBURG, Virginia – Using brassica trap crops may help control harlequin bugs, a common pest of cole crops, and offer an Integrated Pest Management (IPM) method in organic vegetable production.

Anna Wallingford, a graduate research assistant in the Department of Entomology at Virginia Tech, received a $9,523 Southern Sustainable Agriculture Research & Education (SARE) Graduate Student Grant to study the effectiveness of a trap cropping system as an alternative to broad-spectrum foliar insecticide applications to manage the harlequin bug.

The harlequin bug, similar to the stinkbug, is a pierce-sucking insect that feeds on the leaves of cole crops, leaving white blotches and making the crops unmarketable. Heavy feeding pressure can cause the plants to wilt and die.

Wallingford found that a mustard border row trap crop is effective in controlling the harlequin bug in collards, and is likely to provide control in other cash crops of the same species, such as broccoli, cabbage, Brussels sprouts and cauliflower. In addition, the cultural method also reduces the need for broad-spectrum insecticides in cole crops, as the research indicated that an addition of a systemic insecticide made no difference in the amount of damage observed.

“The border rows of mustard were shown to provide effective control of harlequin bug in collards, keeping the feeding damage below 25 percent, which is acceptable in many circumstances,” said Wallingford. “Collard plots with mustard border rows had less harlequin bug damage than plots without mustard border rows.”

Border rows of mustard plants protect cole crops from harlequin bug feeding damage. Trap crops are designed to keep pests away from the cash crop. Photo courtesy of Anna Wallingford, Virginia Tech.

Wallinford conducted lab tests on five brassica crops and one non-brassica crop to evaluate harlequin bug host plant preference for habitation, feeding, oviposition and development. The purpose of the tests, said Wallingford, was to determine which crops could be used in a trap cropping system that would draw insect feeding away from the cash crops.

“The results showed that the mustard plant performed the best, and that was the plant we took to the field for our trap cropping research,” said Wallingford. “The results also helped us to better understand the role of plant and insect cues involved in host plant selection.”

Wallingford said that the male harlequin bug responded to mustard odors in the air, suggesting the bug uses a series of complex olfactory cues to find host plants.

“Once the male finds a desirable host, he releases an aggregation pheromone that attracts additional individuals to the host plant,” said Wallingford. “Such research is important in effectively managing the pest.”

Thomas Kuhar, as associate professor in entomology at Virginia Tech, said that using a trap cropping system might be an effective IPM technique in cole crops.

“Many farmers have already adopted IPM practices by using softer chemicals to control worm pests of cole crops. However, such insecticides aren’t effective in controlling the harlequin bug,” said Kuhar. “Trap cropping may be a really good option to controlling those pests, especially in organic production situations.”

Wallingford said that the trap cropping system might also work for other pest species, such as flea beetles and the diamondback moth.

For more information on the SARE-funded research, “Trap Cropping for Management of Harlequin Bug in Cole Crops,” visit the national SARE projects database and search by project number GS09-081.

Details of Wallingford’s research, Harlequin Bug Biology and Pest Management in Brassicaceous Crops, have also been published in the Journal of Integrated Pest Management.

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Published by the Southern Region of the Sustainable Agriculture Research and Education (SARE) program. Funded by the USDA National Institute of Food and Agriculture (NIFA), Southern SARE operates under cooperative agreements with the University of Georgia, Fort Valley State University, and the Kerr Center for Sustainable Agriculture to offer competitive grants to advance sustainable agriculture in America's Southern region.