Distribution of Tomato Spotted Wilt Virus (TSWV) in Relation to Wild Weedy Hosts and Susceptible Crops Over a Large Agricultural Landscape

Abstract

Tomato spotted wilt virus (TSWV) is an important agronomic and horticultural pest in NC and other parts of the world. Many have speculated that management of weedy species that host the virus may aid in decreasing TSWV occurrence on a farm. In May of 2003 and 2004, weedy species were sampled around six fields, two fields per replication, at the Center for Environmental Farming Systems (CEFS) in Goldsboro, NC, using a 15 m x 15 m grid to map the overwintering pattern of TSWV on the farm. Weeds were tested for TSWV infection and weed density ratings were assigned in each grid cell. Indicator plants (tomato and peanut) were used to map TSWV occurrence within the fields. Thrips movement was monitored with sticky traps to reveal spatial patterns of movement across the farm and, along with indictor plants, were evaluated biweekly through the summers of 2003 and 2004 to monitor temporal movement/occurrence. Plots were located at field edges and in field centers to detect the differences between trivial movement of infected thrips and movement up to 60 m from bordering weedy hosts. TSWV occurrence was equally likely to be found in the center versus the edge plots, revealing that complete eradication of host species up to 60 m from a field may not aid in decreasing TSWV in a field. TSWV occurrence in and around the three replications that were spread across the farm revealed an effect of replication in 2003 when more virus was found in the southern-most replication. Ranunculus sardous (hairy buttercup) tested positive most often compared to all other weed species tested and was also found in the highest density surrounding the southern-most replication.