Brief Summary of Minutes of Annual Meeting

 Steve Loring, Administrative Adviosor for the WERA1007 group, explained a bit more about the program and specifically requested that all participants make sure to talk about the impact of their work. Rebecca Creamer explained a bit about the group and its purpose.  Introductions were made, and the agenda was discussed. 

Rebecca Creamer presented background information on curly top and the beet leafhopper with emphasis on the disease in New Mexico in chile. She discussed the history of the disease in the state, the renaming of the virus and conversion to strains. She mentioned surveys of virus strains in sugarbeets and the frequency of recombinants and host specificity of certain strains. The most common weed hosts for the beet leafhopper in New Mexico are London rocket, which serves as an overwintering host, and Kochia, which serves as an oversummering host.  She discussed her efforts to develop disease prediction models based on the two weeds hosts, and had success with using London rocket growth related to environmental parameters to predict the magnitude of spring beet hopper flights.

Sharon Martinez, former MS student with Rebecca Creamer, reported on her survey of viral diseases of chile in 2014-2015 in several fields in southern New Mexico.  She found that weed presence was highly associated with disease.

Brian Schutte discussed the temperature and moisture requirements for Kochia germination from southern New Mexico.  He explained that the plant is now called Bassia scoparia and that the plant was introduced into the US in the 1800’s.  These are small-seeded and likely short-lived seed that are dispersed locally.  While much seed germinates at low temperatures, other seed within a population required high temperatures for germination.  Kochia has been eradicated from western Australia with a very concentrated effort.  Questions that he posed: Where should we remove Kochia?  From which environments or habitats would it be feasible to remove the plants? What is the best method to kill the plants?  Is it feasible to establish a regional program for control?

Tesneem Nusayr reported on her research that characterized the GroEL homologue produced by the beet leafhopper. The GroEl sequence can be used to separate among the former Homopteran groups.  She showed through bacterial 2-hybrid and beta galactosidase production and PCR capture that the beet leafhopper GroEL binds to the curly top capsid protein, stronger than to begomovirus CP.  The specificity appears to be associated with the viral capsid so that each viral capsid binds slightly differently to GroEL and other HSPs. Expressed purified GroELs from both sources had the correct structure as visualized by TEM. The GroEL and CP were found by confocal to be localized in the head at the salivary glands.

Carl Strausbaugh presented information on the use of the neonicitinoid seed treatment of Poncho Beta for sugarbeets.  Since there is currently a low to intermediate level of plant resistance to curly top, the ability to grow sugarbeets is highly reliant on insecticide treatments.  He finds good coverage for 77 days, then suggests a foliar pyrethroid treatment such as Mustang, which provides at least 2 more weeks of leafhopper control.  Foliar applied neonicitinoid Asana is gives less effective days of coverage. The seed treatment of Poncho Beta give increases in yield of 17-20%, and 5% increase if no curly top is present, because the insecticide also controls early season leafminers and aphids.  Roots of treated plants store better.  That is important because only 1/3 of the crop is processed directly and the great majority is stored.  He also discussed the identification of curly top strains from Idaho and how those have changed over time. For example, BCTV-Svr was found at high levels in 2006, but very low in 2015-2017. In 2016, 60% of infected plants had Worland-like strains (CO and Worland strains), while in 2017, 80% had Worland, 18% CFH, and 18% Cal-Logan strains. He also briefly mentioned that the “new” resistance identified in sugarbeets appears to be recessive and multigenic.

Esteban Molina presented his research on using Phytophthora riparia as a biocontrol agent against curly top on chile.  He showed that root pre-inoculations with P. riparia mycelial solutions decreased the number and viral titer in chile plants Agro-inoculated with a BCTV clone approximately 72 hours later.  The fungus also worked against curly top inoculated with leafhoppers.  Pre-treatment with BABA also was effective, suggesting that BABA and P. riparia are triggering systemic acquired resistance in the chile.

Stephanie Walker presented field perspectives of curly top in New Mexico. She has had significant curly top in her chile trials since 1999. She also noted problems with tomatoes from home gardens. She has had particular problems with transplanted chile plots, since the plants are well spaced and stressed when the beet leafhoppers are leaving their drying winter hosts.  One year the winter host was a spinach plot that was harvested at the time of transplanting, but the plots show the same general trends.  This year, the transplants were sprayed with kaolin clay (Surround), which appeared to lead to lower curly top levels compared to the direct seeded plots.  Carl Strausbaugh suggested treating the seed with Poncho 600 prior to direct seeding to reduce the curly top in those plants as well.

Research Questions/Priorities –

The group discussed the status of the disease, which research topics are important for a particular location and crop, and what our key research priorities would be.  The list below is presented in no particular order.

      Determine where leafhoppers are coming from when they move into the field.  What is the scale of that movement? How far are they moving?

      How far away from a growing field should weeds be removed?  Will regional weed control of a persistent weed problem such as Kochia be effective?

      Trap crops – which crops would be effective to decrease leafhopper movement?

      What percentage of leafhoppers are carrying curly top? Can that be used to improve the predictive model?

      What strains of curly top should be expected if neonicitinoids are banned or lose efficacy?

      Can we target vector transmission aspects to specifically interrupt transmission, perhaps using knowledge of GroEL?

      Can RNAi technology be used to control curly top without producing transgenic plants?

There was a brief discussion as to the location for next year’s meeting.  The preferred location was Davis, CA, 2^nd choice would be Kimberly, ID in mid July.

There was a discussion of officers for the WERA1007 group.  Carl Strausbaugh agreed to serve as chairman of the group.  Rebecca Creamer agreed to serve as secretary for the next year.

Tours-

There was an excellent tour during our half day of meeting.

We toured sugarbeet and chile plots at Leyendecker Plant Science Research Center.

We also toured the Seco Spice dried chile processing plant in Berino, NM, with host Lucas Ogaz.  He also showed conventional and organic chile production fields and some of the weed and curly top problems in those fields.

Collaborative curly top projects for 2017-18 were carried out among Robert Gilbertson, Jennifer Willems, and Bill Wintermantel.  Cooperative projects were carried out between Carl Strausbaugh, and Bill Wintermantel and between Carl Strausbaugh and Alex Karasev.

The group did not publish a report together.  The following curly top related publications were published during the last year:

 Strausbaugh, C.A., Eujayl, I.A., and Wintermantel, W.M. 2017. Beet curly top virus strains associated with sugar beet in Idaho, Oregon, and a western U.S. collection.  Plant Disease 101:1373-1382.

Peinado, S.A., Achata Bottger, J. Chen, L.-F., Gilbertson, R., Creamer, R. 2018. Evidence of curtovirus competition and synergy in co-infected plant hosts.  African Journal of Microbiology Research 12:254-262.

Nusayr, T., Creamer, R. 2017. A novel groel gene from the endosymbiont of beet leafhopper, Candidatus Sulcia muelleri.  African Journal of Microbiology Research 11:1586-1599

Mauricio-Castillo, J. A., Reveles-Torres, L.R., Mena-Covarrubias, J., Arguello-Astorga, G. R., Creamer, R., Franco-Banuelos, A., Salas-Munoz, S. 2017. First Report of beet curly top virus-PeYD associated with a new disease in chile pepper plants in Zacatecas, Mexico.  Plant Disease, 101:513.

Strausbaugh, C.A., and Fenwick, A. 2018. Beet curly top resistance in USDA-ARS Ft. Collins germplasm, 2017. Plant Dis. Manag. Rep. 12:CF002.

Strausbaugh, C.A., and Hellier, B. 2018. Beet curly top resistance in USDA-ARS Plant Introductions Lines, 2017. Plant Dis. Manag. Rep. 12:CF001.

Strausbaugh, C.A., and Wenninger, E. 2018. Foliar insecticides for the control of curly top in Idaho sugar beet, 2017. Plant Dis. Manag. Rep. 12:CF082.

Chen, L-F, Batuman, O., Aegurter, B.M., Willems, J., and Gilbertson, R.L. 2017. First report of curly top disease of pepper and tomato in California caused by spinach curly top strain of Beet curly top virus.  Plant Disease 101:1334.