2012 Annual Report
1a.Objectives (from AD-416):
1. Determine and compare acquisition and transmission characteristics and efficiencies of whitefly- and thrips-transmitted vegetable viruses including Squash vein yellowing virus (SqVYV) and Groundnut ringspot virus (GRSV), respectively.
2. Analyze feeding behavior with electrical penetration graph (EPG) monitoring to determine when during feeding process the viruses are transmitted.
3. Develop and determine effect of vector management strategies on virus transmission.
1b.Approach (from AD-416):
Laboratory, growth chamber and greenhouse experiments will be used with whole plants and leaf discs to determine and compare acquisition and transmission efficiencies for SqVYV and GRSV. These experiments will show how similar (or different) SqVYV and GRSV transmission is by their respective vector, and thus the likelihood of a single, common management strategy being effective for control of both viruses. Multiple species of thrips will be examined for their ability to transmit GRSV to determine which are likely the key vector species. EPG monitoring will be used to analyze feeding behavior. Vector management strategies will be developed for the key vector species and tested for their effect on virus transmission. Such strategies will include repellants, oils and insecticides.
This report is related to objectives: 1. Characterize ecology, biology, epidemiology, molecular genetics, and vector and host (crop and weed) interactions of domestic, exotic, newly emerging, and re-emerging pathogens, and 2. Develop/refine rapid, sensitive reliable detection/sampling methods for pathogens.
Experiments were conducted to determine acquisition of Squash vein yellowing virus (SqVYV) by Bemisia tabaci biotype B after mechanical and/or whitefly inoculation of the host plant. Results were consistent with previous experiments that showed SqVYV can be acquired as early as two days post-inoculation of the source plant and successfully transmitted by whiteflies to a non-infected host plant. Results were presented as a poster at the November 2011 Annual meeting of the Entomological Society of America in Reno, NV.
Whitefly population data collected during two years in watermelon field trials was preliminarily analyzed. Results showed a stratified distribution of the different life stages of whiteflies along the watermelon vines. Oviposition and hence, egg distribution preferentially occurred in the upper third of a watermelon vine. As the plant grows older, small nymphs are concentrated in the second third of the plant and large nymphs in the older third of the plant. These preliminary results have been presented as an oral presentation at the 2012 combined Southeastern/Southwestern Branch Meeting of the Entomological Society of America in Little Rock, AR. Further analysis of the data is being conducted to elaborate a sampling plan for whiteflies in watermelon in Florida.
An Electrical Penetration Graph (EPG) Lab was established. A mini workshop on EPG was organized and conducted in our laboratory in the Entomology and Nematology Department at the University of Florida, Gainesville, with the collaboration from USDA, Parlier, CA. Currently EPG studies are being used to study the feeding behavior of whiteflies on watermelon plants, the effect of SqVYV infection on whitefly feeding behavior, and effect of mixed infections on whitefly feeding behavior and transmission of SqVYV by whiteflies using this technique.