Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/20/2003
Publication Date: 6/30/2003
Citation: RAO, S., COSSE, A.A., ZILKOWSKI, B.W., BARTELT, R.J. AGGREGATION PHEROMONE OF THE CEREAL LEAF BEETLE: FIELD EVALUATION AND EMISSION FROM MALES IN THE LABORATORY. JOURNAL OF CHEMICAL ECOLOGY. 2003. v. 29(9). p. 2165-2175. Interpretive Summary: Our earlier laboratory study identified the aggregation pheromone (species-specific attractant) of the cereal leaf beetle, a serious pest of wheat, oats, and barley in the US. This pest is expanding its range into Middle Atlantic and some Western States. This current study reports the result of field experiments demonstrating that the cereal leaf beetle can be attracted to traps baited with this pheromone. These results are a positive step towards a monitoring system for the early detection of damaging populations of cereal leaf beetles, especially in areas, which have been free of this pest insect. The results are important to small grain growers and local state agencies because a monitoring system would allow them to take pest control decisions based on the actual number of pest insects in their particular area.
Technical Abstract: The previously identified, male-specific compound of the cereal leaf beetle (CLB, Chrysomelidae; Oulema melanopus), (E)-8-hydroxy-6-methyl-6-octen-3-one, was studied further with respect to field activity and emission rate from male beetles. In a five-week field experiment in Oregon, the compound was shown to function as an aggregation pheromone in attracting male and female CLBs migrating from overwintering sites in spring. Traps baited with the synthetic compound (500 micrograms per rubber septum) caught 3.3 times more BLCs than control traps. Lower doses of the pheromone (50 and 150 micrograms) were less attractive than the 500 microgram dose. One relatively abundant, antennally active volatile compound from the host plant (oats), (Z)-3-hexenyl acetate, was also tested in traps but was not attractive, either by itself or as a synergist of the pheromone. Both sexes were captured about equally for all treatments. We also measured daily pheromone emission by male beetles in the laboratory. Individual males feeding on oat seedlings under greenhouse conditions emitted as much as 6 micrograms per day, which is about 500 times higher than had been previously observed under incubator conditions. The pheromone emission rate was at least five times higher during the day than at night, and in one male, emission spanned a period of 28 days. The release rate of synthetic pheromone from the 500 micrograms septa was very similar to the maximum from single males; thus future experiments should evaluate even higher doses. The field results indicate that the pheromone has potential as a monitoring tool for early detection of CLBs as they move from their overwintering sites into newly planted cereal crops in spring.