Seasonal shoot-feeding by Tomicus piniperda (Coleoptera : Scolytidae) in Michigan

Seasonal shoot-feeding by Tomicus piniperda (L.) was monitored at 2-week in tervals on 15 Scotch pine, Pinus sylvestris L., trees from 8 April through 16 November 1994 in southern Michigan. All shoots that showed evidence of I I piniperda attack were removed every two weeks. In 1994, initial spring fl ight of T. piniperda began on 22 March. At least two live T. piniperda adul ts were found on the 15 trees on each sampling date from 8 April through 1 November 1994. In addition, at least one freshly attacked, beetle-free shoo t was found on each sampling date except for 1 November. The greatest numbe rs of newly attacked shoots, with or without adults present, were found fro m mid-June through mid-August. All adults found in April and May were likel y parent adults, while those from June onward were primarily brood adults. Therefore, at all times of the year, live T. piniperda adults can be found on live pine trees, either feeding in the shoots or overwintering at the ba se of the trunk. Implications of these findings are provided in light of th e US federal quarantine on T. piniperda.