The effect of clothianidin on aphids and yellows virus in sugarbeet.
Field experiments were conducted at Broom's Barn, UK, during 1998, 2000 and 2001 to evaluate the efficacy of clothianidin against the virus-transmitting aphids infesting sugarbeet (cv. Impulse in 1998, and cv. Helix in 2000 and 2001). Six plants per plot were inoculated with virus-infective Myzus persicae. Clothianidin applied to pelleted sugarbeet seeds at 30, 45, 60 and 90 g a.i./unit gave excellent control of green aphids for up to 10 weeks after sowing, comparable to the standard imidacloprid seed treatment at 90 g a.i./unit. The incidence of beet mild yellowing virus in the first two years and beet yellows virus in the third year was also significantly reduced. At rates of more than 45 g a.i./unit, virus yellows incidence was consistently but not significantly lower in plots treated with clothianidin than in plots treated with imidacloprid. Sugar yields were significantly higher in all treated plots compared to untreated plots, but there were no significant differences between insecticide treatments, although clothianidin at higher rates performed consistently better than imidacloprid. Clothianidin at the proposed commercial rate gave good control of M. persicae clones that were resistant to other insecticides, including two, which were reported to have some tolerance of imidacloprid. Clothianidin would be a suitable alternative to imidacloprid for aphid and virus yellows control in sugarbeet. However, if resistance to the latter evolved, it is possible that this could also confer resistance to clothianidin.