|NOUT, M - AG UNIV WAGENINGEN NETHER
Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/27/1998
Publication Date: N/A
Interpretive Summary: Sap beetles are pests of corn, dates, figs, and other fruits. It is a goal to manage these pests without heavy reliance on insecticides, but this will require a thorough understanding of the ecology of these insects. The objective of this study was to investigate one aspect of natural beetle behavior. It is known that wounded spots on the host crops are particularly prone to beetle attack and that the microorganisms present can influence the attractiveness of wounds to invading insects. We studied a large number of common yeast species that might grow at such wound sites for production of chemicals that are sap beetle attractants. The yeasts differed greatly in the chemicals they emitted. Ability of a yeast species to ferment the particular sugars present at a wound site strongly influenced how attractive the infection site would become, but the factors affecting beetle attraction are complex. A number of attractive chemicals were identified; some of these were fermentation products, but others were not. The basic information from this study will be useful to scientists and pest management specialists for designing strategies to manage these insect pests.
Technical Abstract: Sap beetles (Coleoptera: Nitidulidae) are pests of a wide variety of crops and are especially attracted to plant materials that are damaged or decomposing. Attraction of the sap beetle Carpophilus humeralis (F.), a pest of maize, was studied using a wide range of yeast species and strains found on maize and other plants. Both chemical emissions and attractiveness to beetles were monitored; yeasts were grown both on sterile media modeled after maize and on a more natural substrate, sweet corn. Nearly all of the yeasts grew well on all media, but many did not generate volatiles attractive to the beetles. Production of attractants was closely associated with the ability of the yeasts to ferment the sugars present in the medium. Thus Saccharomyces cerevisiae and Candida shehatae, which can ferment corn sugars, were more attractive than Canadida guilliermondii, which cannot, when grown on sweet corn. Volatile production was monitored by GC, using solid-phase microextraction (SPME) as the sampling technique. Typical fermentation-related volatiles were ethanol, acetaldehyde, 2-methyl-1-propanol, 1-propanol, ethyl acetate, 3 methyl-1-butanol, and 2-methyl-1-butanol. However, other potent attractants were also emitted that were not correlated to fermentation ability, such as 3-hydroxy-2-butanone. Thus the factors influencing attractiveness of a crop wound site are complex.