IMPACT OF LATE-SEASON ORANGE-STRIPED OAKWORM (LEPIDOPTERA, SATURNIIDAE) DEFOLIATION ON OAK GROWTH AND VIGOR

The orangestriped oakworm, Anisota senatoria (J. E. Smith), has caused widespread defoliation of urban oak (Quercus) species in southeastern Virginia. The hypothesis that consecutive years of late-season defoli ation by A. senatoria would cause a significant reduction in Quercus g rowth and vigor was tested from 1987 to 1990. Late-season A. senatoria defoliation had a significant impact on Quercus growth and vigor. Pin oak, Q. palustris (Muenchhausen), and willow oak, Q. phellos L., plan ted in fabric containers, had significant reduction in growth with inc reased defoliation. Starch content and tree vigor in Q. palustris, pla nted in the urban landscape, was significantly reduced with increased defoliation, and some tree mortality occurred. Quercus phellos was a h ardier species compared with Q. palustris and was not significantly af fected by consecutive late-season defoliation. In addition, data sugge sted that Q. palustris was affected more by A. senatoria late-season d efoliation when trees were planted in stressed urban sites. These data have important implications for A. senatoria management strategies. H igh populations that have the potential to cause 100% late-season defo liation during consecutive years should be controlled to prevent progr essive decline in tree health.