2009 Annual Report

Adult eucalyptus longhorned borer on a red blossom of eucalyptus.
Photo by Jack Kelly Clark.

Entomologists use ‘love potions’ to control cerambycid beetles

UC and University of Illinois scientists have tripled the number of known pheromones that attract several species of pest cerambycid, or longhorned, beetles. Traps containing cheap, generic blends of these chemicals, which insects emit to attract mates, help growers monitor and control populations that are low or difficult to survey.

Wood-boring beetles from this family include many species that attack and kill fruit trees, ornamental trees and shrubs, and timber; they also damage wood in buildings.

Longhorned beetle larvae emerge from eggs laid in protected places on bark, feed on the inner bark, then bore into the sapwood or heartwood, killing branches or entire trees. These beetles also can transmit nematodes, fungi, and other pathogens that can kill host trees.

One nematode, Bursaphelenchus xylophilu, which pinesawyer beetles vector, causes pine wilt disease, which has devastated pine forests in Japan and China; the disease also occurs throughout most of the United States. Cerambycids also are likely to transmit pitch canker and other fungal diseases by contaminating feeding and oviposition wounds with fungal spores.

UC Riverside entomologist Jocelyn Millar and University of Illinois entomologist Larry Hanks have successfully identified pheromone blends for more than 30 species, including several invasive pests. They also have shown that adult beetles of another 10 species apparently don’t use pheromones but are attracted by volatile chemicals the host trees release.

“Little was known about the chemical ecology of cerambycid beetles or their use of attractant pheromones before this project,” Millar said. “The pheromones of only a few species had been identified. Our longer-term goals are to gain a better understanding of which subfamilies, tribes, and genera are likely to use pheromones and within those groups to determine the types of chemicals that are used as pheromones. This will allow us to predict whether new invaders are likely to use pheromones that we can exploit, and if so, what those pheromones are likely to be.”

During the second year of this three-year project, the research group identified two diagnostic characteristics, one behavioral and one morphological, that will enable researchers to immediately assess whether a species is likely to have a male-produced attractant pheromone. The study also found the first examples of powerful female-produced pheromones in the Cerambycidae family.

“These morphological features and specific behaviors are reliably associated with pheromone use by cerambycid beetles,” Millar said. “So from simply observing the behavior of a new invasive cerambycid species, regulatory personnel can assess whether it uses attractant pheromones that can be identified and exploited for its detection and management.”

The study also showed that many cerambycid species produce large amounts of pheromone—hundreds of micrograms during a few hours.

“This is critically important for lure design, because lures must release 5 to 25 milligrams of pheromone per day to be effective,” Millar said. “This is in marked contrast to pheromone lures for other insect species, where release rates are typically a few micrograms per day. We are working to develop lures for field use that are capable of these high release rates for extended periods (weeks).”

Funding for this project came from the UC Exotic/Invasive Pests and Diseases Research Program.

Contact

Jocelyn Millar, (951) 827-5821

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