Life History and Damage of the Pine Root Tip Weevil, Hylobius rhizophagus,1 in Wisconsin2

Abstract

H. rhizophagus Millers (Coleoptera: Curculionidae), is one of the factors contributing to pine plantation deterioration. The weevil was found in the central and northwestern counties of Wisconsin and in parts of Michigan, where it poses a threat to all low-vigor plantations of jack pine, Pinns banksiana Lamb. While jack pine is the preferred host of the weevil, red pine, P. resinosa Ait.; Scotch pine, P. sylvestris L.; and eastern white pine, P. strobus L., are damaged when grown adjacent to jack pine. The weevil overwinters in larval and adult stages. Adults emerge from hibernation in late April to feed and mate. Eggs are laid in the soil in July near root tips and on primary lateral roots, and they hatch in late June and early July. Larvae feed in the roots until soil temperatures fall below 11°C and resume feeding when temperatures rise above 11°C. Pupation occurs from late June into August. Transformation to the adult occurs in late July through August. New adults feed until the onset of temperatures below 11°C. Adults overwinter twice and larvae once. Numbers of weevils on jack pine root systems ranged from 1 to 29, with an average of 7.2/tree. Natural control of the weevil was slight; only 1 predator, larvae of an elaterid beetle, Melanotus sp., was found feeding on the weevil larvae in the roots.