Disruption of trans-pityol-mediated attraction by racemic trans-conophthorin in twig beetle Pityophthorus pubescens

Twig beetle Pityophthorus pubescens (Coleoptera: Curculionidae: Scolytinae) has been previously associated with the Fusarium circinatum (Hypocreales: Nectriaceae), the pathogen causing pitch canker disease, in P.radiata stands of the Basque Country (Northern Spain). Laboratory and field studies were conducted to evaluate the response of the insect to the racemic mixture of the spiroacetal trans-7-methyl-1,6-dioxaspiro[4.5]decane, also known as conophthorin. In walking bioassays, addition of 10 and 100ng of racemic trans-conophthorin to 1ng of (+/-)-trans-pityol elicited a negative response in males, whereas females did not show any significant preference. Catches of males in attractant-baited traps were strongly reduced by racemic trans-conophthorin at all release rates tested (0.5, 1.0, 1.5 and 2.0mg/day). In contrast, catches of females were not affected by any of the (+/-)-trans-conophthorin release rate.