Biology and management of bark beetles (Coleoptera: Curculionidae) in Washington cherry orchards

The biology and management of bark beetles (Coleoptera: Curculionidae, Scolytinae) in Washington cherry orchards was investigated from 2003-2005. Two dominant species were identified attacking cherry (Prunus spp.) orchards: the shothole borer, Scolytus rugulosus Müller, and an ambrosia beetle, Xyleborinus saxeseni Ratzeburg. S. rugulosus was the species most implicated in damage to healthy trees. Two distinct periods of S rugulosus activity occur in Washington, with a possible partial third in some locations. The first activity period begins in late April and peaks in late May to early June, with the second beginning in mid-July and peaks in late July to early August. Yellow sticky traps (unbaited apple maggot traps) were effective tools to monitor S. rugulosus activity but ethanol-baited intercept-style traps were necessary to monitor X. saxeseni activity. Movement of S. rugulosus into orchards was closely associated with emergence from outside hosts, generally a pile of recently pruned or cut wood placed outside the orchard. S. rugulosus readily moved distances of 10-50 m to attack trees on orchard borders, but did not move more than two or three rows into a healthy orchard. A residue bioassay technique demonstrated that several insecticides caused mortality of S. rugulosus adults. A pyrethroid, esfenvalerate, was the most active 21 d after treatment. Azinphos-methyl was acutely toxic to S. rugulosus, but for only seven d. Endosulfan and the neonicotinyls, thiamethoxam and acetamiprid, were somewhat toxic to S. rugulosus