Influence of Host Resistance and Insecticide Seed Treatments on Curly Top in Sugar Beets.

Curly top on sugar beets (Beta vulgaris) caused by Beet severe curly top virus or closely related species is a considerable problem in arid growing regions of the western United States. Two insecticide seed treatments, Poncho Beta (60 g a.i. clothianidin + 8 g a.i. beta-cyfluthrin/100,000 seed) and Gaucho (45 g a.i. imidacloprid/100,000 seed), and four sugar beet hybrids varying in curly top resistance were evaluated for their influence on the control of curly top in comparison with untreated checks. Plots were established at two locations in southern Idaho in 2005 and evaluated for curly top. Moderate to severe curly top due to natural inoculum and leafhopper infestations occurred at both locations. Untreated, the four hybrids performed as expected with the fewest curly top symptoms on PM21 and the most on Monohikari. Both insecticide treatments lowered curly top ratings compared with the untreated check, but Poncho Beta reduced symptoms more than Gaucho as the season progressed. Poncho Beta led to increased yield and estimated recoverable sugar across all hybrids at harvest, particularly on the more susceptible hybrids. When considering the yield parameters for only the most resistant hybrids individually, Poncho Beta did not always outperform Gaucho. Poncho Beta provided a level of control that would justify its application as a supplement to host resistance under Idaho conditions.