Comparison of volatiles from beetle-transmittedCeratocystis fagacearum and four non-insect-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 includedXerula radicata Sing,Pluteus atricapillus Kumm,Tyromyces chioneus Karst, andBotrytis cinerea. Nitidulids have been reported in association with each of these fungi, but unlikeC. fagacearum, they are dispersed primarily by wind or rain. Significant attraction of three nitidulid species,Carpophilus hemipterus (Linne),C. lugubris Murray, andStelidota geminata (Say) was elicited byC. fagacearum and to a lesser extent byX. radicata, but not by the others. A comparison of headspace volatile profiles showed that the odor ofC. fagacearum was the strongest, both with regard to the number of components and in their rates of production. Chemical characterization of the headspace profile ofC. 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.