REDUCED OFFSPRING PRODUCTION IN BARK BEETLE TOMICUS-PINIPERDA IN PINEBOLTS BAITED WITH ETHANOL AND ALPHA-PINENE, WHICH ATTRACT ANTAGONISTIC INSECTS

Bolts of Scots pine, Pinus sylvestris L., attacked by the bark beetle Tomicus piniperda (L.) were baited with ethanol and a-pinene to attrac t antagonistic insects and thereby enhance their detrimental effects o n the production of bark beetle progeny. Unbaited and caged bolts were included in the experiments as controls. Attraction of beetles to the bolts and subsequent emergence were estimated using traps. Six phloem -feeding species (potential competitors of T. piniperda) and four pred atory species were caught in significantly higher numbers at the baite d bolts than at the unbaited ones. The number of offspring and the pro ductivity of T piniperda were four to seven times higher in unbaited b olts than in baited bolts. Exclusion of other insects, by using cages, resulted in a nine-fold increase in the number of T. piniperda offspr ing per square meter and productivity (offspring per egg gallery) comp ared with unbaited, exposed bolts. Hylurgops palliatus (Gyll.) (Scolyt idae) and Rhagium inquisitor (L.) (Cerambycidae) attacked both the bai ted and unbaited bolts, whereas Acanthocinus aedilis (L.) (Cerambycida e) and Pytho depressus (L.) (Pythidae) reproduced almost exclusively i n the baited ones. Large numbers of larvae of Thanasimus (Cleridae) an d Rhizophagus (Rhizophagidae) emerged from both the baited and unbaite d bolts. Adults of Plegaderus vulneratus (Panzer) and Cylister lineari s (Er.) (Histeridae) emerged almost exclusively from the baited bolts. The low progeny production of T piniperda in the baited bolts was att ributed largely to the influence of adults of Rhizophagus and Epuraea (Nitidulidae), and larvae of Thanasimus and A. aedilis.