New Ingredient Improves Pheromone Lure for Brown Marmorated Stink Bug
By Ed Ricciuti
“Attract and kill” sounds like a tactic used by special operations military forces, but it is actually a method relied upon by pest managers in the war against injurious insects. By luring individuals of a pest species to one spot, they can be targeted specifically with chemical controls, reducing the amount of insecticides applied to crops and the impact on beneficial species, explains Kevin Rice, Ph.D., of the United States Department of Agriculture (USDA).
It makes sense that the more effective the lure, the better the tactic works. “More sensitive lures can improve monitoring or biosurveillance tools for detection of target pest organisms more quickly and reliably and can improve behaviorally based management strategies such as attract-and-kill,” says Rice.
Rice and colleagues at the USDA’s Agricultural Research Service (USDA-ARS), together with several partnering scientists, have described their efforts to improve an attractant used to collect the invasive brown marmorated stink bug (Halyomorpha halys, also known by its acronym BMSB) in research published in December in the Journal of Economic Entomology.
Researchers seeking to improve the effectiveness of attractants continually tinker with chemicals that insects use to communicate, especially pheromones, those that trigger a physiological or behavioral response by conspecifics, i.e., members of the same species. Often, research involves extremely fine tuning, because even a slight chemical change in the structure or components of a chemical molecule can significantly change the behavior of insects. Sometimes, it is a case of mix and match, combining chemicals or adding one to an attractant already in use, an approach that has been tried on the BMSB.
Native to Asia, BMSB appeared in Pennsylvania during the 1990s and has spread to 48 states and parts of Canada. It preys on 300 different plants and has caused massive damage, both to commercial agriculture and backyard gardens.
USDA-ARS scientists have tried combining different chemicals with a pheromone compound, dubbed PHER, containing epoxy and bisabolen, produced by the males of BMSB, to kick up its power. PHER is called an “aggregation pheromone,” because it attracts conspecifics of both sexes to the location of the insect that emits it. Although not a sexual attractant per se, but rather serving to draws bug together, as to food, it presumably also enhances the chances that the sexes will hook up and reproduce. USDA-ARS scientists identified and deciphered its chemical structure in 2014.
One chemical that has been tested with PHER is a methyl compound called MDT for short. MDT is the aggregation pheromone of the oriental stink bug Plautia stali. It successfully captured H. halys adults and nymphs in the latter part of the growing season, but only nymphs early in the season, making planning for long-term control difficult.
However, MDT and PHER work synergistically when combined, attracting more insects than when alone and for a longer seasonal time period. In apple orchards, traps baited with PHER and MDT have been successfully used to help plan pest management and as the basis for attract-and-kill strategies.
Rice and his colleagues tried to find if other compounds with a chemical structure similar to that of MDT also boosted the aggregation phenome’s attractiveness. These included two ethyl compounds, known as EDT and EDD. Both are esters, or odoriferous liquids. EDD is found in many fruits, including apple and pear, and is used to make products such as perfumes.
They found that PHER and EDT worked well, while alone neither was effective. Better yet, the combination worked throughout the growing season. From early through mid-season, the combination caught more adults than traps baited with other attractants or none at all. As the season progressed, the attractive power of the combination continued to be high.
The researchers noted that both EDT and MDT provoke a response when tested with a technique called electroantennography—a tool for measuring the potency of pheromones by measuring the difference in electrical potential between the tip and base of an insect’s antenna when exposed to an odor. The authors of the paper speculate that the similar response may be due to the similar chemical structures of the two compounds or that EDT, like MDT, could be a pheromone produced by another stinkbug species and is cross-attractive to BMSB.
Be that as it may, the researchers conclude: “Overall, EDT enhanced the response of H. halys adults and nymphs to its aggregation pheromone season-long.”
Journal of Economic Entomology
Ed Ricciuti is a journalist, author, and naturalist who has been writing for more than a half century. His latest book is called Bears in the Backyard: Big Animals, Sprawling Suburbs, and the New Urban Jungle (Countryman Press, June 2014). His assignments have taken him around the world. He specializes in nature, science, conservation issues, and law enforcement. A former curator at the New York Zoological Society, and now at the Wildlife Conservation Society, he may be the only man ever bitten by a coatimundi on Manhattan’s 57th Street.