COMPARISON OF VOLATILES FROM BEETLE-TRANSMITTED CERATOCYSTIS-FAGACEARUM AND 4 NONINSECT-DEPENDENT FUNGI

Ceratocystis fagacearum (Bretz) Hunt is the causative agent of oak wilt disease, which is transmitted primarily by nitidulid beetles. This fungus was compared with four non-insect-dependent fungi for their volatile profiles using gas chromatography and mass spectrometry (GC-MS) and for their attractiveness to nitidulids using a wind-tunnel bioassay. The four additional fungi included Xerula radicata Sing, Pluteus atricapillus Kumm, Tyromyces chioneus Karst, and Botrytis cinerea. Nitidulids have been reported in association with each of these fungi, but unlike C fagacearum, they are dispersed primarily by wind or rain. Significant attraction of three nitidulid species, Carpophilus hemipterus (Linne), C. lugubris Murray, and Stelidota geminata (Say) was elicited by C fagacearum and to a lesser extent by X. radicata, but not by the others. A comparison of headspace volatile profiles showed that the odor of C fagacearum was the strongest, both with regard to the number of components and in their rates of production. Chemical characterization of the headspace profile of C. fagacearum revealed 16 components: one aldehyde, one ketone, five alcohols, and nine esters. These components were all common fruit-odor constituents and many of them were previously shown to be attractive to nitidulid beetles. The results of this study suggest that, by mimicking food odors, C fagacearum odor is an adaptation for attracting nitidulid and possibly other insect vectors.