Management of whitefringed beetle (Coleoptera: Curculionidae) grub damage to sweet potato with adulticide treatments.

Field experiments in sweet potato, Impomoea batatas (L.) Lamarck, were done to evaluate the impact of insecticides applied to foliage on whitefringed beetle ( Naupactus spp,) adult and larval populations and on larval feeding damage to sweet potato roots. Analysis of transformed data combined over all sample dates in 1994 indicated that adult means in both the weekly and biweekly spray treatments were significantly lower than in the nontreated control plots, and nonparametric analysis indicated that adult means were significantly lower in the weekly insecticide treatment. Counts of adults combined over all 1996 sample dates were significantly lower in all adulticide treatments compared with the non treated control. In 1994, numbers of whitefringed beetle grubs in soil core samples were significantly lower in the adulticide treatments compared with the non treated plots, indicating that adulticides had an indirect negative effect on the offspring larval population, The mean percentages of sweet potato roots damaged by larval feeding were lower in the weekly or biweekly adulticide treatments (carbaryl plus methyl parathion) than in the nontreated control in 1994 (differences not significant) and in 1995 (differences were significant). In 1996, root damage was significantly lower in plots sprayed weekly with phosmet or carbaryl than in nontreated plots, In 1997, root damage in nontreated plots averaged >2.5-fold greater than in the insecticide treated plots, but differences among treatments were not significant. Collectively, these results indicate that application of adulticides may be an effective alternative to soil insecticides for management of whitefringed beetle in sweet potato.