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

Abstract

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.

Control of Curly Top in Sugar Beet with Seed and Foliar Insecticides

“…The Poncho seed treatments (all nine) also led to a 18 and 21% increase in recoverable sucrose compared with the untreated check in 2012 and 2013, respectively, which is consistent with previous results (25,28). Compared with the untreated check in August, the Poncho seed treatments (all nine) reduced the curly top rating by 42 and 26% in 2012 and 2103, respectively.…”

“…In an effort to supplement host resistance, neonicotinoid seed treatments (23,(25)(26)(27)(28) have been successfully used to ameliorate curly top, beginning with the 2006 growing season. Some commercial production areas experienced large yield increases (20% or more) and the neonicotinoid seed treatments are now required on all commercial sugar beet seed in some of these growing areas (28).…”

“…In an effort to find a way to supplement host resistance, in-furrow, foliar, and seed-treatment insecticides have been investigated (12,14,16,23,25,26,28,30). Based on these investigations, the neonicotinoid seed treatments (active ingredients: clothianidin and thiamethoxam) have shown the most potential to limit curly top and to increase yields (23,(25)(26)(27)(28).…”

“…Based on these investigations, the neonicotinoid seed treatments (active ingredients: clothianidin and thiamethoxam) have shown the most potential to limit curly top and to increase yields (23,(25)(26)(27)(28). Under low to moderate curly top pressure, the neonicotinoid seed treatments have been shown to increase yields by approximately 20% through providing earlyseason control of the beet leafhopper, the vector for BCTV (25). In some production areas in the western United States, the neonicotinoid seed treatments are now required on all sugar beet seed because of the low level of host resistance in commercial cultivars and the yield increases associated with the seed treatments (28).…”

Sugar Beet Cultivar Evaluation for Storability and Rhizomania Resistance

“…clothianidin + 8 g a.i. betacyfluthrin/100,000 seed) and standard cultural practices (26). The plants had a very low curly top rating of 1 at the end of the growing season using a disease index (26) of 0 to 9, where 0 = healthy and 9 = dead.…”