Brief Summary of Minutes of Annual Meeting

Speakers were Greg Walker, Candace Stafford, Rebecca Creamer, Carl Strausbaugh. Carl Strausbaugh spoke about screening for resistance to BCTV in sugarbeets and screening insecticides for efficacy in controlling BCTV. The screening results will be published soon in Phytopathology. Poncho Beta by Bayer, at a cost of $23/acre appears to be the best seed treatment for curly top since it gives 60 days on control compared to 30 days of control with Gaucho. Predicting leafhopper numbers in Idaho is difficult, but high numbers appears to be related to warm temperatures in March. Candace Stafford discussed the EPG waveform patterns associated with beet leafhopper feeding patterns. Patterns D2/D3 and G are associated with honeydew production. Pattern A had positive amplitude and was of variable length, pattern B1 had negative amplitude and was for 1 min., pattern B2 was for 30 sec, pattern C has positive amplitude and was for minutes, and pattern D1 had primarily negative amplitude and only half of the leafhoppers monitored showed this pattern. Patterns D2, D3, and D4 were highly variable with D4 occurring within D2 or D3. D3 was associated with honeydew formation of 0.08 drops/min and a pH of 7-8, suggesting the leafhoppers were feeding in the phloem. Pattern G was associated with honeydew production of 0.3 drops/min and a pH of 4-5, suggesting the leafhoppers were feeding on xylem. Patterns D2 and D3 are thought to be associated with phloem ingestion and D1 is association with phloem salivation and virus inoculation into the phloem. Leafhoppers spent only 1% of their time in D1, 52% of their time in D2+D3, and 8% of their time in G. If the leafhoppers had already fed in xylem, then they took about 1 in to progress to D1. If not hydrated, the leafhoppers fed on xylem for 30 min before going to phloem feeding. Q. Does the monitoring results help explain the broad host range for the beet leafhopper? A. Maybe since the leafhopper spends so much time feeding in the xylem, that would allow it to feed on the xylem of many different plants. Carl Strausbaugh talked about BCTV identification in sugarbeets from a regional survey. In Idaho, the beet leafhoppers cycle is a bit different from that reported in California. The leafhoppers lay eggs in March. There were symptoms of BCTV on the roots of sugarbeets also, characterized by small roots with vascular discoloration. In Colorado, they found mostly BMCTV; Idaho and Oregon had small amounts of BCTV. That was unusual since BCTV (Cal/Logan) has not been found elsewhere. In Montana and Wyoming, all samples were infected with both BMCTV and BSCTV. Greg Walker discussed the biological control of beet leafhoppers using parasitic wasps. Four wasps were found, Anagrus nigriventris, Aphelinoidea zarehi, Polynema sp., and Paracentrobia. The last three insects are trichogramid wasps. A. nigriventris worked well on London rocket, but was found in highest numbers in sugarbeet fields. The highest levels of parasitization was found during the summer. Aphelinoidea was found in highest numbers in Russian thistle in July- Sept, while Paracentrobia was found in highest numbers during the same time on Chenopodium. Discussion topics Q. Who did the early work on migration and parasitization? A. Henderson of the USDA in the 1950s. Q. Is it possible to test stylet sheaths for virus? A. If leafhoppers are fed on parafilm and the sucrose is extracted for virus or tested by PCR, it should work. It might work to test corn that has leafhoppers attached with a clip cage. Q. Are the saliva components of the beet leafhopper known? A. No Q. Are symptoms of curly top temperature dependent? A. Beans appear to grow out of the symptoms in cool conditions. Carl Strausbaugh volunteered to host our next meeting in Twin Falls, Idaho in July-August 2008.

Several funded collaborative projects on curly top are ongoing among working group members. The first, by Creamer and Walker, funded by the Southwest Consortium looks at transmission of curly top by the beet leafhopper to resistant tomato varieties. The second, by Hanson and Strausbuagh, funded by the Chile Commission, is a screening for resistance to curly top in chile peppers. A third collaborative project is with Gilbertson, Wintermantel, and Clark compares viral infection in insects with plant infection. The participants who are actively involved in curly top research agreed try to submit their current work for publication during the upcoming year.

No publications for 10/2006 to 8/2007.