Issue No. 18, Article 2/July 25, 2008
Japanese Beetle Management: What's on the Horizon?
Over the past several years, the Japanese beetle has become a key insect pest, one that corn and soybean producers dread and have come to expect by midsummer. The pest's very large host range also means that homeowners across Illinois encounter Japanese beetles feeding on many of their ornamental plants. In short, a pest once characterized as occasional is now seemingly a perennial threat. Since 1916, when Japanese beetles were first found in southern New Jersey, they have spread throughout much of the eastern half of the United States. However, isolated pockets have been found as far west as California. With the great diversity of crops in California at potential risk, this insect pest is monitored every season, and entomologists are prepared to implement eradication efforts if necessary.
A paper recently published (online on June 25, 2008) offers some hope for the future regarding a novel management technique for this important insect pest (Proceedings of the National Academy of Sciences of the United States of America, "Chiral Discrimination of the Japanese Beetle Sex Pheromone and a Behavioral Antagonist by a Pheromone-Degrading Enzyme," by Yuko Ishida and Walter S. Leal).
Researchers at the University of California at Davis, led by Walter Leal, a professor of entomology and chemical ecology, have "isolated, identified, cloned, and expressed an antennae-specific pheromone-degrading enzyme" from Japanese beetles. Their research indicates that the enzyme quickly inactivates the sex pheromone of Japanese beetles. As Leal's team indicates, the olfactory system of this insect is quite sophisticated. Two olfactory receptor neurons are located on the antennae of male Japanese beetles. One neuron is sensitive to the sex pheromone emitted by Japanese beetle females [(R)-japonilure]. The second is sensitive to (S)-japonilure, a sex pheromone released by the Osaka beetle, Anomala osakana. The ranges of these beetles overlap in Japan, their native habitat. When the sex pheromone of the Osaka beetle was blended with (R)-japonilure in synthetic formulations, captures of male Japanese beetles declined.
Ultimately, this exciting research is aimed at reducing or preventing detection by Japanese beetle males of the sex pheromone emitted by females. I believe it holds promise for improved management strategies. As we learn more about these studies, we will share the findings with our readers. For now, continued vigilance in scouting corn and soybean fields is recommended for the next several weeks.--Mike Gray