Control of Soil Insect Injury by Resistance in Sweet Potato

Abstract Soil insect root injury to resistant sweet potato [ Ipomoea batatas (L.) Lam.] cultivars ‘Regal’ and ‘Southern Delite’ was compared to injury to ‘Jewel’ and ‘Centennial’ in trials with the resistant-standard W-13 and the susceptible-standard SC 1149-19. Injury by three groups of insects was evaluated: the wirewoom -Diabrotica-Systena complex (WDS), which includes the southern potato wireworm ( Conoderus falli Lane), the tobacco wireworm ( C. vespertinus Fabricius), the banded cucumber beetle ( Diabrotica balteata LeConte), the spotted cucumber beetle ( D. undecimpunctata howardi Barber), the elongate flea beetle ( Systena elongata Fabricius), the pale-striped flea beetle ( S. blanda Melsheimer), and S. frontalis Fabricius (a flea beetle); the sweet potato flea beetle ( Chaetocnema confinis Crotch.); and a white grub ( Plectris aliena Chapin). Relative control estimates were obtained by comparison to the susceptible standard. ‘Regal’ and ‘Southern Delite’ provided good control of all three insect groups with control of all insect injuries of 79.2% and 81.0%, respectively. ‘Jewel’ and ‘Centennial’ were resistant to the sweet potato flea beetle and sustained less damage by WDS than the susceptible standard, but would still be classed as susceptible to WDS. ‘Centennial’ was as susceptible to the white grub as SC 1149-19. The levels of resistance demonstrated for ‘Regal’ and ‘Southern Delite’ would provide growers an alternative to insecticides for the control of these insects.