Effects of seeding rate and cultivar on tomato spotted wilt of peanut

Tomato spotted wilt, caused by thrips-vectored Tomato spotted wilt virus (TSWV), is a very serious problem in peanut (Arachis hypogaea L.) production in the southeastern U.S. Establishment of within row plant densities of 13 or more plants/m of row of moderately resistant cultivars is recommended as part of an integrated management system for minimizing losses to spotted wilt. To achieve that plant density, growers often plant 19 or more seed/m of row. Seed costs represent a major expense for peanut producers. Reducing costs by using lower seeding rates would be desirable if it could be done without increasing risk of losses to tomato spotted wilt. Field experiments were conducted in Tifton, Georgia in 2008 and 2009 to determine whether new cultivars with improved field resistance to TSWV can allow use of lower seeding rates without increasing risk of losses to tomato spotted wilt. In each year, peanut cultivars, Georgia Green, Georgia-06G, Florida-07, and Tifguard were combined factorially with four seeding rates, 9.8, 13.1, 16.4, and 19.7 seed/m of row. Across the two years, final incidence of tomato spotted wilt and standardized area under the disease progress curve for tomato spotted wilt epidemics decreased linearly with increasing seeding rate for all cultivars. Across the two years, final incidence of tomato spotted wilt at 9.8 seed/m of row seeding rate was 55% for Georgia Green and 17% for the mean of the other three cultivars. For Georgia Green, incidence of tomato spotted wilt decreased 1.9% with each seed/m increase in seeding rate, whereas the incremental decrease was 0.8% for the mean of the other three cultivars. These results indicate that levels of field resistance to TSWV in several new cultivars are adequate to allow use of lower seeding rates than with the moderately resistant cultivar Georgia Green without increasing the risk of losses to spotted wilt.