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Title: Emergence of root-feeding weevils (Coleoptera: Curculionidae) in central Georgia peach orchards

Author
item Cottrell, Ted
item HORTON, DAN - University Of Georgia

Submitted to: Journal of Entomological Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/10/2012
Publication Date: 7/1/2013
Citation: Cottrell, T.E., Horton, D.L. 2013. Emergence of root-feeding weevils (Coleoptera: Curculionidae) in central Georgia peach orchards. Journal of Entomological Science. 48(3):184-194.

Interpretive Summary: External insect feeding injury on peach roots was observed and it was not consistent with known injury caused by the peachtree borer. This damage was suspected to be the result of one or more species of root-feeding weevils. To determine what insects may be causing this injury, we used conical emergence traps to sample insects emerging from the orchard floor in unsprayed peach orchards. Traps were placed within the dripline of trees and at missing tree sites, where few peach roots would extend. Adult Fuller rose beetle, Naupactus cervinus (Boheman), whitefringed beetles, Naupactus spp. and the twobanded Japanese weevil, Callirhopalus bifasciatus, (Coleoptera: Curculionidae) were captured at significantly higher numbers within the dripline of the tree than at missing tree sites. Fuller rose beetle adults emerged from soil during all months of the year; whereas, the other two species emerged during the growing season. In commercial peach orchards comprised of cultivars with early, mid, and late-season fruit ripening dates, Fuller rose beetle was the most abundant. Although cultivars with different fruit-ripening dates may receive a different number of insecticide applications before fruit are harvested, we did not detect a difference in Fuller rose beetle emergence between these cultivars. In another sprayed orchard, Fuller rose beetle was again more common in traps than other curculionid spp.. Root damage ratings (0 to 5) revealed a mean rating of 2.79 ± 0.12. Year-long emergence of adult Fuller rose beetle is likely why it persisted in sprayed orchards. Modification of existing pest management programs will be need if Fuller rose beetle causes economic injury to peach roots.

Technical Abstract: Injury to peach roots is common by several plant pathogen species and by larvae of the peachtree borer, Synanthedon exitiosa Say (Lepidoptera: Sesiidae). External feeding injury to peach roots was observed that was not consistent with S. exitiosa injury but was suspected as a result of larval root-feeding weevil spp. (Coleoptera: Curculionidae). Thus, we used conical emergence traps for 3 yr to sample in unsprayed peach orchards (within the dripline of trees and at missing tree sites, where few peach roots would extend). Fuller rose beetle, Naupactus cervinus (Boheman), whitefringed beetles, Naupactus spp. and the twobanded Japanese weevil, Callirhopalus bifasciatus, (Coleoptera: Curculionidae) were captured at significantly higher numbers within the dripline of the tree than at missing tree sites. Adult N. cervinus emerged from soil year around; whereas, the other two species had seasonal emergence. In commercial peach orchards comprised of cultivars with early, mid, and late-season fruit ripening dates, N. cervinus was much more abundant than other species. The later a cultivar ripens, the higher the number of insecticide applications it receives, however, we did not detect a difference in N. cervinus emergence between the cultivars. In another sprayed orchard, N. cervinus was again more common in trap captures than other cucrculionid spp. Root damage ratings (0 to 5) revealed a mean rating of 2.79 ± 0.12. Year-long emergence of N. cervinus is likely why it persisted in sprayed orchards. Modification of existing pest management programs will be needed to manage N. cervinus attacking peach roots.