Synergism of Turpentine and Ethanol as Attractants for Certain Pine-Infesting Beetles (Coleoptera)

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Abstract
Responses of seven species of pine-infesting beetles to traps baited with either turpentine, ethanol, turpentine and ethanol released from separate dispensers, or a 1:1 solution of turpentine and ethanol released from one dispenser were assessed in three field experiments. The weevil species, Pachylobius picivorus (Germar), and the cerambycid pine sawyer, Monochamus carolinensis (Olivier), were attracted to turpentine and were unaffected by the addition of ethanol. The ambrosia beetle, Xyleborus affinis Eichhoff, responded to ethanol alone but was not attracted to turpentine, nor did the presence of turpentine significantly affect its response to ethanol. The remaining four species displayed responses to turpentine that were enhanced by the addition of ethanol, but in different ways according to the method of deployment. Hylobius pales (Herbst) weevils and M. titillator (F.) sawyers displayed greatest attraction to turpentine and ethanol whether they were released from side-by-side dispensers or as a solution from one dispenser. The black turpentine beetle, Dendroctonus terebrans (Olivier), displayed the highest response to turpentine and ethanol in solution. The ambrosia beetle, X. pubescens Zimmermann, responded in low numbers to turpentine or ethanol deployed singly, but displayed an enhanced response (20-fold increase) to turpentine and ethanol deployed side-by-side and an even greater response (60-fold increase) to a solution of turpentine and ethanol. Reasons for increased responses by some species to a solution of turpentine and ethanol over the two released separately are not clear; they may lie in different dosages or evaporation rates of volatiles in the field. Laboratory analyses of trapped headspace volatiles from dispensers containing only turpentine and those containing a solution of turpentine and ethanol revealed no differences in the amounts of four principal monoterpene hydrocarbons (α-pinene, camphene, β-pinene, and limonene) released over time. The synergistic effect of turpentine and ethanol for some species and not others may point to ecological differences between species with regard to the condition of preferred host material.