WERA1007: Curtovirus Biology, Transmission, Ecology, and Management
(Multistate Research Coordinating Committee and Information Exchange Group)
Status: Inactive/Terminating
Date of Annual Report: 07/25/2017
Report Information
Period the Report Covers: 10/01/2016 - 09/30/2017
Participants
Rebecca Creamer (creamer@nmsu.edu) - New Mexico State University, Entomology,Plant Pathology and Weed Science
Al Poplawsky (alpop@uidaho.edu) - University of Idaho, Dept of Plant Pathology
Jennifer Willems (Jennifer.willems@cdfa.ca.gov) - California Dept of Food and Ag/BCTV
Control Program
Lauren Murphy (lauren.murphy@cdfa.ca.gov) - California Dept of Food and Ag/BCTV Control
Program
Tesneem Nusayr (tessamn@nmsu.edu) - New Mexico State University, Molecular Biology
Carl Strausbaugh (carl.strausbaugh@ars.usda.gov) - USDA-ARS, Kimberly, ID
Quaid Dobey (quad09@nmsu.edu) - New Mexico State University, Entomology, Plant
Pathology, and Weed Science
Phillip Miklas – (phil.miklas@ars.usda.gov) - USDA-ARS, Prosser, WA
Alvaro Soler – (alvaro.solergarzon@wsu.edu) - Washington State University, Prosser, WA
Marjo Ala-Poikela (marjoa@uidaho.edu) - University of Idaho, Dept of Plant Pathology
Thomas Koeps (Thomas.koeps@kws.com) - Betaseed Inc, Kimberly, ID
Kylie Swisher – (kylie.swisher@ars.usda.gov) - USDA-ARS, Prosser, WA
Becky Cochran (becky.cochran@ars.usda.gov) - USDA-ARS, Prosser, WA
Randy Collins (randy.collins@cdfa.ca.gov) - CDFA/BCTV Control Program
Silvia Rondon (silvia.rondon@aregonstate.edu) - Oregon State University
Jim Crosslin (voncross263@gmail.com) - retired USDA
Gaylord Mink (gmink@charter.net) - retired Washington State University
Naidu Rayapati (naidu@wsu.edu) - Washington State University, Prosser, WA
Brief Summary of Minutes
Phillip Miklas welcomed the group to the USDA/WSU Prosser Station. Rebecca Creamer explained a bit about the group and its purpose. Introductions were made, and the agenda was discussed. Steve Loring, administrator 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.
Carl Strausbaugh presented background information on curly top and the beet leafhopper with emphasis on the disease in Idaho on sugarbeets. He also presented information on the symptoms and factors that influence the symptoms. In Idaho there are three generations of leafhoppers; the 1st in the desert with migration out mid May – June 1. He reported on his recent publication on the sequencing of curly top isolates collected through 2006-2007 and 2012-2015 surveys of infection of curly top in sugarbeets. Overall he found 11 BCTV strains based on whole genome sequencing: SvrPep (NM), Kim1, LH71, Mild, Wor, CO, Cal/Logan, Svr(CFH), PeCT, SpCT, and PeYD. The Mild, Worland, and CO strains formed a group, while the LH71, and Kim1 grouped together in a different clade. He found that the two Kim1 isolates are recombinants between Wor and Svr parents with the most variability in the V3, C2 and C3, and beginning of C1 regions. Idaho currently has primarily CO, Wor, and Cal/Logan strains, compared to the formerly large amounts of Svr that are now very reduced.
Carl also discussed the use of neonicitinoid seed treatment of Poncho for sugarbeets. He finds good coverage for 77 days, then suggests a foliar pyrethroid treatment of Mustang or Asana. The seed treatment of Poncho , Cruise or Nipsit are very effective leading to large increases in yield of 17-20% because the insecticides also control leafminers and aphids.
Marjo Ala-Poikela from Alex Karasev’s laboratory presented her characterization of a BCTV isolate from Chihuahua, Mexico. ELISA positive samples were subjected to PCR and sequencing. She found a putative recombinant with mild strain as a major parent, and severe strain as a minor parent. The region of the genome highly similar to the severe strain included C1 and C4. A 1.53-mer infectious clone was produced and used for agroinoculations. Compared to the control infections, it was less virulent than both mild and severe strain on sugarbeet, showed similar virulence as mild strain on tomato, but didn’t infect beans.
Gaylord Mink commented that poor symptoms of curly top in glass greenhouses had been detected at WSU in the past. They found that the plants appeared to need UV to get symptoms since, if tomato plants were grown under Lucite plastic (the type that yellows), they got symptoms, while they did not if grown under glass.
Alan Poplawsky from Alex Karasev’s laboratory reported on the host range of curly top infectious clones. He found the CFH and Logan clones gave severe symptoms on susceptible sugarbeets, while the ID-Wor and Mex clones gave minimal symptoms on sugarbeets. When they tested the same clones on the universal susceptible sugarbeet Monohikari, he found that the Logan clone killed the sugarbeets, the CFH clone began to kill the Monohikari, but plants had recovered by 10 weeks. In comparison the ID-Worland clone gave slow low level of infection, but was dead by 10 weeks, and the Mexican clone gave slow low infection, but never killed the plants. A resistant sugarbeet, Kdh-13 either showed initial resistance to infection, a decreased rate of infection, or recovery after 10 weeks depending on the clone used for infection. There are thus likely three types of resistance found in sugarbeets, 1) resistance to initial infection, 2) limitation of the rate of infection to a very slow progression, and 3) initial severe disease but then a near complete recovery. He also reported on the symptoms of the clones in tomatoes, which were stunting, leaf curling, and discoloration which included chlorosis and vein purpling on the back of leaves. He reported that the Logan clone killed all tomato varieties, CFH infection was low (27%) and progressed slowly, and Mex and ID-Wor gave intermediate levels of infections (38%) and progressed fairly slow.
Alvaro Soler from Phillip Miklas’ laboratory talked about his work on searching for the curly top resistance gene in beans. He reported that Andean bean germplasm have fewer genes than Central American gemplasm because of repetitive DNA and stress response, although both have 11 chromosome pairs. In the Andean lines, the Bct gene for resistance is found on chromosome 7, while another marker for resistance can be found on chromosome 6. He screened bean germplam using agroinoculation of bean through needle inoculation and found that the Bct resistant phenotype was in 60% of 367 snap bean lines. He also looked for better Bct resistance markers on genome 7, by looking for other genes around the scar marker. He found an exonuclease that explains 99% of phenotypic variation, so is likely a good marker. Bct resistance explains 30% of variation in bean golden mosaic and 77% of variation for reaction to bean dwarf mosaic virus.
Naidu Rayapati talked about grapevine leafroll disease in Washington. Grapes are grown primarily in central and eastern Washington on self-rooted grapevines (no phylloxera present). There are both wine and juice grapes grown, however, the acreage and production of the wine grapes has greatly expanded to 270,000 tons of wine grapes harvested from 60,000 acres, worth $4.8 million. Approximately 60% are red grapes (merlot, cabernet) and 40% are white grapes (Riesling, chardonnay). Symptoms of grapevine leafroll virus are only present in the wine grapes and only obvious in red grapes, but the others are infected. Symptoms only appear after grape ripening, when the red color is forming. A decrease in photosynthesis is found in red grapes that is associated with symptom production. GLRaV is semipersistently transmitted by mealybugs and soft scale insects. Most GLRaV are ampeloviruses, but GLRaV-2 is a closterovirus, and GLRaV-7 is a velarivirus. Washinton grapes are mostly infected with GLRaV-3 (86.8%), but there are small levels, 5%, of GLRaV-2 and GLRaV-4. His lab has produced an infectious clone of GLRaV-3, but must co-infiltrate with a silencing suppressor to get infection.
Tesneem Nusayr reported on her experiments that characterize the GroEL produced by the beet leafhopper. She showed that the endosymbionts from the beet leafhopper produce GroEl that differs from the GroEL from other hoppers. 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 E. coli GroEL also binds to curly top CP, but not well to begomovirus. Expressed purified GroELs from both sources had the correct structure as visualized by TEM. There was interest from the group about producing transgenic plants containing GroEL to block leafhopper transmission.
Kylie Swisher discussed the role of beet leafhopper in BLTVA transmission. In northern Oregon, increased trap catches of BLH are found in June. Sugarbeet and radish are good hosts for the BLH and potato is an intermediate host allowing good survival. In 2007-2009 curly top was detected in the BLH. In 2002, potato purple top was found, which is caused by infection with BLTVA. It was not found for the next 10 years. In 2016, there was lots of BLTVA, but the distribution in the field was not the same as with the BLH and there were very low numbers of BLH. There were very high numbers of potato psyllids, suggesting that maybe they were transmitting BLTVA.
Kylie also reported on her work on a survey of peppers and weeds from central Mexico, Zacatecas state. She found BLTVA and curtoviruses and psyllids and leafhoppers. Sequence of the curtoviruses showed that they were PeCTV and PepSvr. She also found phytoplasmas in the psyllids collected from Zacatecas.
Quaid Dobey talked about his research, looking at the temperature and moisture requirements for Kochia germination from southern New Mexico. He found increased Kochia germination associated with a variable temperature regime of lower temperatures that was then transferred to higher temperatures, than when retained at the lower temperatures. He showed that there is very decreased germination with extremely high moisture stress. He found that the BLH feeding preference was to the largest Kochia in greenhouse and field cage experiments. He also found that Kochia emergence in the field is now 2-3 months earlier that it was 5-6 years ago.
Jennifer Willems gave an update on curly top in California and the control board management efforts. For updates on BCTV control in California, subscribe to BCTV at http://www.cdfa.ca.gov/subscriptions/. Sprays were done aerially on 64,450 acres in spring 2016, but there was no fall 2016 aerial campaign due to the large amount of rain. There was lots of rain in December 2016, which caused the growth of lots of grass and weeds in the foothills. The BLH did not appear to overwinter on the Central Valley floor. There was lots of rain in January and February 2017 also. There were minimal BLH numbers in Dec-Feb and weeds did not really dry down. Curly top was found in 33/46 leafhoppers and 17/113 plants collected from Fresno in March. There was no spraying other than roadsides in Fresno and Kings Co, and only 4,000 acres were sprayed in Kern Co.
Field reports of curly top were sent from Utah, by Claudia Nischwitz and from New Mexico sent by Stephanie Walker. Curtoviruses came in very late into Utah at the end of June and beginning of July. Individual fields had losses of up to 40% on tomatoes and 25% on gourds. Beans and beets also tested positive. In New Mexico, there was mid level severity of curly top with 3-5% infection in most locations and 10% in a few key growing areas. Some organic chile fields had 30% infection. A high level of infection, 40%, was found in transplanted chile at the university research farm, while adjacent direct seeded chile had very low levels of infection.
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.
Mapping of virulence factors in BCTV
Interaction between BCTV and resistance genes
Interaction between BCTV and different weed species
Prediction model for California, New Mexico
Quick field test for curly top for growers to use in the field for tomatoes
Clones of other curly top strains to allow a geographic location by strain analysis
Determine the driving force behind virus strain changes
Determine where leafhoppers are coming from when they move into the field. What is the scale of that movement? How far are they moving?
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?
There was a brief discussion as to the location for next year’s meeting. The preferred location was Davis, CA, 2nd choice would be Las Cruces, NM
Tours-
There was an excellent tour during our half day of meeting.
Horse Heaven Hills
Bean breeding plots (We found curly top and phytoplasma)
Medicago breeding cages, cherry trees and hops
Greenhouse with potyvirus resistance experiments
Accomplishments
<p>Collaborative curly top projects for 2015-16 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.</p>Publications
<p>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.</p>Impact Statements
- The group has made an impact on better understanding and controlling curly top in the western U.S. The resistance of various crops and varieties to curly top was assessed, the curly top virus strains and virus prevalence for particular areas were characterized, and the relationship between viruses and specific weed hosts was assessed.
Date of Annual Report: 06/22/2018
Report Information
Period the Report Covers: 06/15/2017 - 06/19/2018
Participants
Rebecca Creamer (creamer@nmsu.edu) - New Mexico State University, Entomology,Plant Pathology and Weed Science
Tesneem Nusayr (tnusayr@gmail.com) - University of Houston, Biology
Carl Strausbaugh (carl.strausbaugh@ars.usda.gov) - USDA-ARS, Kimberly, ID
Tiffany McKay-Williams (tmckay@betaseed.com) - Betaseed Inc, Kimberly, ID
Steve Loring (sloring@nmsu.edu) - New Mexico State University – AES
Carol Sutherland (csutherl@nmsu.edu) - Extension Plant Science – NMSU
Anita Rodriguez (anita@nmsu.edu) - NMSU – Mktg/PES
Vince Hernandez Biad Chile – Rezolex, Las Cruces, NM
Brian Schutte (bschutte@nmsu.edu) - NMSU, EPPWS
Stephanie Walker (swalker@nmsu.edu) - NMSU, EPS
Nina Dropcho (ndropcho@nmsu.edu) - NMSU (PES)
Janel Titzl (jtitzl@nmsu.edu) - NMSU
Israel Jovkhadar (icalsoya@nmsu.edu) - NMSU
Jose Araiza (jaraizac@nmsu.edu) - NMSU
Samantha Overcasher (samovar@nmsu.edu) - NMSU
Sharon Martinez (orion.skywalker@gmail.com) - NMSU, EPPWS
Lucas Ogaz (secospice@secospice.com) Seco Spice, Berino, NM
Esteban Molina (molina93@nmsu.edu) - NMSU, EPPWS
Jennifer Randall (jrandall@nmsu.edu) - NMSU, EPPWS
Hormat Rhein (hshadgou@nmsu.edu) - NMSU, Molecular Biology
Kimberly Cervantes (kcervan5@nmsu.edu) - NMSU, Molecular Biology
Erik Lehnhoff (lehnhoff@nmsu.edu) - NMSU, EPPWS
Brief Summary of Minutes
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, 2nd 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.
Accomplishments
<p>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.</p>Publications
<p>The group did not publish a report together. The following curly top related publications were published during the last year:</p><br /> <p> <strong>Strausbaugh</strong>, C.A., <strong>Eujayl</strong>, I.A., and <strong>Wintermantel</strong>, 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.</p><br /> <p>Peinado, S.A., Achata Bottger, J. Chen, L.-F., <strong>Gilbertson</strong>, R., <strong>Creamer</strong>, R. 2018. Evidence of curtovirus competition and synergy in co-infected plant hosts. African Journal of Microbiology Research 12:254-262.</p><br /> <p>Nusayr, T., <strong>Creamer</strong>, R. 2017. A novel <em>groel</em> gene from the endosymbiont of beet leafhopper, Candidatus <em>Sulcia muelleri</em>. African Journal of Microbiology Research 11:1586-1599</p><br /> <p>Mauricio-Castillo, J. A., Reveles-Torres, L.R., Mena-Covarrubias, J., Arguello-Astorga, G. R., <strong>Creamer</strong>, 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.</p><br /> <p><strong>Strausbaugh,</strong> C.A., and Fenwick, A. 2018. Beet curly top resistance in USDA-ARS Ft. Collins germplasm, 2017. <em>Plant Dis. Manag. Rep.</em> 12:CF002.</p><br /> <p><strong>Strausbaugh,</strong> C.A., and Hellier, B. 2018. Beet curly top resistance in USDA-ARS Plant Introductions Lines, 2017. <em>Plant Dis. Manag. Rep.</em> 12:CF001.</p><br /> <p><strong>Strausbaugh,</strong> C.A., and Wenninger, E. 2018. Foliar insecticides for the control of curly top in Idaho sugar beet, 2017. <em>Plant Dis. Manag. Rep.</em> 12:CF082.</p><br /> <p><strong>Chen, L-F, </strong>Batuman, O., Aegurter, B.M.,<strong> Willems, J., and Gilbertson, R.L. </strong>2017. First report of curly top disease of pepper and tomato in California caused by spinach curly top strain of <em>Beet curly top virus</em>. Plant Disease 101:1334.</p>Impact Statements
- Curly top is an economically important disease in many states in the western U.S. Members of the WERA1007 group increased the knowledge of the virus biology, its transmission, and the management of the disease. The range of virus strains was expanded in California, Idaho, Oregon, and Mexico. The resistance to curly top in sugarbeets was assessed, aspects of the curly top virus transmission were characterized, and the use of foliar insecticides for vector control was tested.
Date of Annual Report: 07/02/2019
Report Information
Period the Report Covers: 06/20/2018 - 06/19/2019
Participants
Creamer, Rebecca (creamer@nmsu.edu) - New Mexico State University, Entomology,Plant Pathology and Weed Science
Tesneem Nusayr (tnusayr@gmail.com) - University of Houston, Biology
Carl Strausbaugh (carl.strausbaugh@ars.usda.gov) - USDA-ARS, Kimberly, ID
Tiffany McKay-Williams (tmckay@betaseed.com) - Betaseed Inc, Kimberly, ID
Jennifer Willems (Jennifer.willems@cdfa.ca.gov) - California Dept of Food and Ag/BCTV Control Program
Bill Wintermantel (bill.wintermantel@ars.usda.gov) - USDA-ARS, Salinas, CA
Christian Nansen (chrnansen@ucdavis.edu)
Hyoseok Lee (blueorange23@snu.ac.kr)
Brief Summary of Minutes
Jennifer Willems welcomed the group to the CDFA office in Clovis, CA. Rebecca Creamer explained a bit about the group and its purpose. Introductions were made, and the agenda was discussed.
Bill Wintermantel gave an overview of curly top in California. He reported on the curly top strains in tomatoes and sugarbeets in California and Idaho. He noted that new BCTV variants are emerging in California and displacing traditional forms of BCTV and suggested that the change could be due to the virtual elimination of sugarbeet cultivation in the Central Valley of CA. Since sugarbeet is a favored host of the beet leafhopper, then BCTV strains that do best on sugarbeet are found in low frequency, if at all. BCTV-Svr replicates better on sugarbeet than BCTV-Mld; while the reverse is true for tomato. BCTV mild replicates significantly better on bean and Shepherds purse than BCTV-Svr. The movement on the beet leafhopper in California can be separated into two components – long distance movement from the foothills (up to 400 miles has been reported) and localized in field movement. Mitigating factors for BCTV epidemiology in CA are the wide host range of virus and vector, the relatively high leafhopper populations most years, the abundance of uncultivated lands, and the poor stands of crops providing open areas. Disease management in sugarbeets has been improved by elimination of volunteer beets, the use of insecticides, and the use of resistant varieties.
Jennifer Willems gave an update on the curly top problem in California and the control board management efforts. For updates on BCTV control in California, subscribe to BCTV at http://www.cdfa.ca.gov/subscriptions/. Plantago > peppergrass > filaree are the preferred overwintering hosts for the beet leafhopper, in that order. January and February 2019 were very rainy and thus germinated abundant grasses. There was a small BLH hatch in March and more of a drydown of the weeds in April, which led to spring spraying. Spraying is generally timed for a local population consisting of around 85% nymphs and 15% adults. Most of the spraying is done with fixed wing aircraft, with spot treatments done with a ground rig. In 2019 there was spraying of 9,815 acres out of a possible 30,000 acres, so a very minor curly top year and small acreage sprayed.
Carl Strausbaugh showed symptoms used in rating BCTV losses in sugarbeet. He presented results on the use of the neonicitinoid seed treatment 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 neonicitinoid seed treatments. He finds good control against BCTV for 77 days using Poncho Beta, Cruise, or NipsIt. He finds a 17-20% yield increase if BCTV is present and 5% yield increase if BCTV is not present (early season control of leafminers and aphids, along with reduction of root maggots, thrips, and cutworms). Treated roots store better than untreated roots. A foliar pyrethroid treatment such as Mustang or Asana will provide at least 2 more weeks of leafhopper control and can be tank mixed with herbicides. Foliar applied pyrethroids were tested using 6 hoppers/plant with plants at 8 leaf stage for sugarbeets without any resistance. Plants were sprayed one week before leafhoppers were introduced. Truvia (stevia sugar substitute) was effective against black bean aphids. He also discussed the identification of curly top strains from Idaho and how those have changed over time. For example, in 2014, 2015, and 2016 mostly BCTV-Wor-like isolates were found infecting sugarbeets, while in 2017 around 17% CFH and CA/Logan isolates were identified and in 2018, around 50% were infected with BCTV-Wor-like and 50% with Ca/Logan. He suggested that the change in isolates could be due to the treatment of all sugarbeets with Poncho, so that the leafhoppers would likely be moving BCTV from dry beans or weeds.
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.
Rebecca Creamer presented information on the relative levels of curly top strains in chile and weeds from 2001 through 2015. PeYDV was detected in 2001 and 2003 with higher levels compared to BCTV-mild or BCTV-Svr NM. PeCTV was discovered in 2005 and levels have increased such that 77% of the chile tested in 2015 had PeCTV. BCTV-CO was found for the first time in 2018 on sugarbeets, while BCTV-Wor and BCTV-PeCT were found on leafhoppers. 2019 has been a very high curly top and leafhopper year thus far in New Mexico. By mid April, yellow sticky trap catches had yielded more than 1100 leafhoppers on four traps and that increased to over 2000 leafhoppers at the beginning of May and over 2500 leafhoppers at the beginning of June. 2019 will likely be the year with the largest numbers of leafhoppers in southern New Mexico since 2001 when leafhopper trapping was initiated. Curly top incidence in some commercial chile fields was already at 40-50% in early June.
Hyoseok Lee spoke about his research modeling beet leafhopper reproductive capacity on different hosts common to CA. Reproduction temperature optima were the same on different hosts, with sugarbeet providing the highest level of reproduction of the BLH, followed by plantago, and filaree, which provided lower reproductive potential. That matches the feeding preferences found in the field also. He also spoke briefly about the merits of various trap crops for use in CA.
Christian Nansen discussed the proximal remote sensing and how it works. He explained how reflectance was used to differentiate beet leafhoppers carrying BCTV-Svr from nonviruliferous hoppers. The hoppers bodies needed to be exposed, so wings and legs were removed and the exact angle and lighting was very important. This work was recently published in Plant Pathology in May 2019.
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.
Developing and improving predictive models for each state/system. Need long term prediction models also. Will test individual leafhoppers for virus and monitor leafhopper movement at each location to help fine tune models.
What percentage of leafhoppers are carrying curly top and what BCTV strain(s) are they carrying? Can we use the spectral analysis method to determine infectivity status for field samples. Group will plant joint project to test field collected leafhoppers by spectral analysis, then by PCR. Could send the leafhoppers back and forth in 70% EtOH. This will also allow comparisons of the BLH populations.
Trap crops – which crops would be effective to decrease leafhopper movement?
CDFA would like a quick easy field test for infected leafhoppers.
What are alternatives to the insecticides used for BLH control, particularly to malathion?
Is sugarbeet resistance to BCTV strain specific?
Sugarbeet industry would like high throughput phenotyping, durable resistance to BCTV and novel resistance with clear markers.
Bill Wintermantel invited the group to an international Geminivirus meeting, which he and Bob Gilbertson will be hosting in Davis, CA Nov. 9-13.
There was a discussion of officers for the WERA1007 group. Carl Strausbaugh agreed to serve for another year as chairman of the group. Rebecca Creamer agreed to serve as secretary for the next year.
There was a brief discussion as to the 2020 meeting location. Carl Strausbaugh agreed to host the meeting in Kimberly, ID. The meeting date will tentatively be set for July 14 with July 15 as a field day.
Accomplishments
<p>Collaborative curly top projects for 2018-19 were carried out among Robert Gilbertson, Christian Nansen, and Bill Wintermantel. Cooperative projects were carried out between Carl Strausbaugh, and Bill Wintermantel and between Carl Strausbaugh and Alex Karasev. Carl Strausbaugh is also currently conducting two cooperative projects with Erik Wenninger. Rebecca Creamer is currently conducting a cooperative project with Stephanie Walker.</p>Publications
<p>The group did not publish a report together. The following curly top related publications were published during the last year:</p><br /> <p> </p><br /> <p>Martinez, S., Creamer, R. Thomas, S., and Schroeder, J. 2019. Assessment of Weed/pest complexes in southern New Mexico chile fields. NMSU AES Research Report – RR794.</p><br /> <p> </p><br /> <p>Nansen, C., Stewart, A. N, Gutierrez, T.A.M., Wintermantel, W.M., McRoberts, N., and Gilbertson, R.L. 2019. Proximal remote sensing to differentiate nonviruliferous and viruliferous insect vectors – proof of concept and importance of input data robustness. Plant Pathology 68: 746-754.</p><br /> <p> </p><br /> <p>Strausbaugh, C.A., and Hellier, B. 2019. Beet curly top resistance in USDA-ARS Plant Introductions Lines, 2018. <em>Plant Dis. Manag. Rep.</em> 13:CF050.</p><br /> <p> </p><br /> <p>Strausbaugh, C.A., and Fenwick, A. 2019. Beet curly top resistance in USDA-ARS Ft. Collins germplasm, 2018. <em>Plant Dis. Manag. Rep.</em> 13:CF051.</p><br /> <p> </p><br /> <p>Strausbaugh, C.A., and Wenninger, E. 2019. Foliar insecticides for the control of curly top in Idaho sugar beet, 2018. <em>Plant Dis. Manag. Rep.</em> 13:CF052</p>Impact Statements
- Curly top is an economically important disease in many states in the western U.S. Members of the WERA1007 group increased the knowledge of the virus biology, its transmission, and the management of the disease. The range of virus strains was expanded in California, Idaho, Oregon, and Mexico. The resistance to curly top in sugarbeets was assessed, aspects of the curly top virus transmission were characterized, and the use of foliar insecticides for vector control was tested. These findings should help improve the management of curly top in sugar beet and other affected crops in the western U.S.
Date of Annual Report: 07/28/2020
Report Information
Period the Report Covers: 06/19/2019 - 07/14/2020
Participants
Creamer, Rebecca (creamer@nmsu.edu) - New Mexico State University, Entomology,Plant Pathology and Weed Science
Tesneem Nusayr (nusayrt@uhv.edu) - University of Houston, Biology
Carl Strausbaugh (carl.strausbaugh@ars.usda.gov) - USDA-ARS, Kimberly, ID
Tiffany McKay-Williams (tmckay@betaseed.com) - Betaseed Inc, Boise, ID
Laurne Murphy (lauren.murphy@cdfa.ca.gov) - California Dept of Food and Ag/BCTV Control Program
Bill Wintermantel (bill.wintermantel@ars.usda.gov) - USDA-ARS, Salinas, CA
Christian Nansen (chrnansen@ucdavis.edu) University of California, Davis, Entomology
Hyoseok Lee (blueorange23@snu.ac.kr) University of California, Davis, Entomology
Brian Schutte (bschutte@nmsu.edu) - NMSU, Entomology, Plant Pathology, and Weed Science
Alex Karasev (alexander.karasev@uidaho.edu) University of Idaho, Entomology, Plant
Pathology, and Nematology
Erik Wenninger (erikw@uidaho.edu) University of Idaho, Entomology, Plant Pathology, and
Nematology
Amanda Skimore (skid@nmsu.edu) New Mexico State University, Extension Plant Science
Punya Nachappa (punya.nachappa@colostate.edu) Colorado State University, Agricultural
Biology
Thomas Koeps (Thomas.koeps@kws.com) KWS SAAT Ag, Twin Falls, ID
Kylie Swisher (kylie.swisher@ars.usda.gov) USDA-ARS, Wapato, WA
Silvia Rondon (silvia.rondon@oregonstate.edu) Oregon State University
Stephanie Walker (swalker@nmsu.edu) New Mexico State University, Extension Plant Science
Erik Lehnhoff (lehnhoff@nmsu.edu) NMSU, Entomology, Plant Pathology, and Weed Science
Carrie Wohleb (cwohleb@wsu.edu) Washington State University Extension
Zach Bagley (zach@tomatonet.org) California Tomato Research Institute
Ana Cristina Fulladolsa Palma (ana.fulladolsa_palma@colostate.edu) Agricultural Biology
Athena Kvamme (athenak@nmsu.edu) New Mexico State University
Akash Bajagain (bajagain@nmsu.edu) NMSU, Entomology, Plant Pathology, and Weed Science
Steve Loring (sloring@nmsu.edu) NMSU College of Agricultural, Consumer, Environmental Science
Gina Angelella (gina.angelella@usda.gov) USDA-ARS, Wapato, WA
Imad Eujayl (imad.eujayl@usda.gov) USDA-ARS, Kimberly, ID
Raj Majumdar (raj.majumdar@usda.gov) USDA-ARS, Kimberly, ID
Dennis Lozada (dlozada@nmsu.edu) NMSU, Plant and Environmental Science
Judith Chiginsky (judith.chiginsky@colostate.edu) Colorado State University, Agricultural
Biology
Tiziana Oppedisano (oppdist@oregonstate.edu) Oregon State University
Brief Summary of Minutes
Carl Strausbaugh, WERA1007 Chair, welcomed the group to the virtual meeting. Rebecca Creamer, WERA1007 Secretary, explained a bit about the group and its purpose. Introductions were made, and the agenda was discussed.
Steve Loring, NMSU ACES, gave the Administrative Advisor report. He reminded us that meeting reports are due 60 days after the meeting. He also told the group that he will be stepping out of the group and all similar advisory roles by September 1 and plans to retire. The new Administrative Advisor will be Sreekala Bajwa, Dean of the College of Agriculture and Agricultural Experiment Station Director at Montana State University (agdean@montana.edu).
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 the problems encountered in 2019 with very high levels of leafhoppers and high incidence of curly top, and the management strategies that were successful despite the severe leafhopper/disease pressure.
Research Priorities and Ideas
-Alternatives to neonicitinoid seed treatments
-Novel sources of disease resistance
-Need centralized database for leafhopper trapping results. Sweeps or sticky traps? Include the size of sticky card? What height or placement and direction of card? Dates and locations? Host plants for sweeps?
-Silvia Rondon suggested looking at green bridge, what are the overwintering sources, beet leafhopper movement in the landscape.
-Imad Eujayl wants colonies of leafhoppers that carry single virus strains to use for strain specific resistance testing.
-Christian would like to have a shared leafhopper resource information database. It would include who has colonies, whether the colonies are carrying curly top or not and what strain(s) are present.
- Christian has healthy and BCTV-Svr-infected leafhopper colonies.
- Imad and Carl have infected colonies with mixtures of 3 strains. BCTV-Svr (CFH), Cal-Logan, and smaller amounts of BCTV-Wor and BCTV-CO.
- Punya Nachappa has a matched set of Idaho leafhopper colonies with and without BCTV-Svr virus and field collected hoppers from Colorado that are likely virus-free.
There were several suggestions as to the host plants that would allow multiple virus strains to remain in a population. Rebecca suggested adding weeds such as Kochia or London rocket to colonies. Tesneem Nusayr suggested using spinach.
Punya Nachappa suggested that the WERA1007 group should apply for an SCRI (Specialty Crop Research Initiative) CAP (Coordinated Agriculture Projects) grant for one of the crops that is a problem for curly top, such as peppers, tomatoes, beans or other specialty crops. Christian was supportive of the idea.
Hyoseok Lee would like historical data or field observation data on leafhopper data, sticky cards and sweeps data, GPS location, date, and numbers of leafhoppers collected.
Tesneem Nusayr and Imad Eujayl are looking for uninfected beet leafhoppers that are growing on sugarbeets.
Zach Bagley offered a support letter for anyone writing a SCBG on tomatoes from the California Tomato Research Institute.
There was a brief discussion as to the 2021 meeting location. Carl Strausbaugh agreed to host the meeting in Kimberly, ID. The meeting date will tentatively be set for a hybrid meeting (online/in person) on Tuesday July 13, 2021 with July 14 as a field day/nursery tour.
WERA1007 will need to be renewed. The renewal is due by January 15. These projects run for 5 years. Carl Strausbaugh, Christian Nansen, and Punya Nachappa will help with the renewal process.
Carl Strausbaugh will serve for another year as chairman of the group. Rebecca Creamer will serve as secretary for the next year.
Accomplishments
<p> Athena Kvamme presented her research on BCTV strains identified from New Mexico chile and leafhoppers (swept from Kochia) in 2019. She found more than 40% of samples were infected with BCTV-Wor or BCTV-PeCT (or mixed infections of the two strains) and smaller amounts (10%) with BCTV-PeYD, (2%) with BCTV-CO or BCTV-LH71. The leafhoppers contained only the strains found with more than 10 % infection.</p><br /> <p> </p><br /> <p>Alex Karasev presented on a collaborative research on BCTV infection on potato. They inoculated Yukon Gold potatoes with cloned BCTV strains using agroinoculation. They found that primary inoculation (agroinoculation) of Cal-Logan (75%) or CFH/Severe (63%) caused symptoms on potato after 4-5 weeks, but not yield losses, while Worland and Mexican Mild did not infect or show symptoms. He found that the plants resulting from secondary infection (plants that resulted from infected tubers) showed much higher levels of infection of Cal-Logan (90%) and CFH/severe (67%) and much stronger symptoms (stunted and curled leaves) and tuber yield losses (weight of tubers/plant).</p><br /> <p> </p><br /> <p>Punya Nachappa presented data on curly top infection of hemp in Colorado in 2019. Disease was identified from 11/12 counties in Colorado. Symptoms of curly top on hemp include chlorosis, curled leaves, leaf scorch, mild leaf curl, flat leaf lamina, and significant yield losses. BCTV-CO, BCTV-Mild, and BCTV-Wor or mixed infections of the strains were most prevalent in the samples and symptoms were not associated with a specific BCTV strain. Some asymptomatic plants also were infected with BCTV. Other viruses were also found infecting the plants. The beet leafhopper does not appear to be reproducing on hemp.</p><br /> <p> </p><br /> <p>Akash Bajagain presented his research on the effects of mustard cover crops on disease and weeds in chile. He also monitored the effect of mustard cover crop termination on leafhopper flights. Highest biomass of mustard was found with the latest termination date (April 4), and leafhopper numbers did not increase until May. The second and third termination dates (March 17 and April 4) were effective in decreasing number of weeds.</p><br /> <p> </p><br /> <p>Carl Strausbaugh reported on foliar insecticide treatments for management of curly top on sugar beets. None of the foliar insecticides tested were any better than the untreated checks. He also reported on their research to sample leafhoppers trapped from yellow sticky traps from sugarbeet and bean fields and desert areas from eight sites. Leafhoppers were highest (423) in desert areas in Elmore County in August. Leafhoppers were highest (9) in sugarbeets in Elmore County in July. Leafhoppers were highest in beans (23 and 56) in Elmore County in July and September and Canyon County (42) in August. 51% of the leafhoppers collected in July and August were BCTV positive, with 83% of the positives from Treasure Valley. 70% of the positives contained BCTV-Wor or BCTV-CO, 11% Cal-Logan, and 6% CFH (Severe). BCTV-Mild-containing leafhoppers were equally found in all three test areas (sugarbeets, beans, desert), while the 3 BCTV-Svr samples came from beans and sugarbeet, and the 6 BCTV-Cal-Logan samples came from sugarbeets. Comparing the mtCoi from the leafhoppers showed that there are two different biotypes of leafhoppers from Idaho, one of which matched the sequence from New Mexico.</p><br /> <p> </p><br /> <p>Christian Nansen discussed the proximal remote sensing and how it works. He explained how reflectance was used to differentiate beet leafhoppers carrying BCTV-Svr from nonviruliferous hoppers. The hoppers bodies needed to be exposed, so the exact angle and lighting is very important. He requested beet leafhoppers collected by sweep net from specific plant hosts, put into 70% ethanol and sent to him. He would like to test field-collected hoppers in his system noted with location, date, and host plant.</p><br /> <p> </p><br /> <p>Hyoseok Lee spoke about his research on predicting spring migration time of the beet leafhopper using satellite imagery in California. In California, overwintered beet leafhoppers migrate from the foothills to crop fields in the spring. We hypothesized vegetation conditions in the foothills trigger the spring migration. Since 2019, the spring migration of the leafhoppers was monitored at three different foothills using yellow sticky cards. For measuring the vegetation conditions, NDVI (Normalized difference vegetation index) and EVI (Enhanced vegetation index) of the foothills were calculated using satellite imagery. Field observation data were normalized and then correlated with NDVI and EVI using a Jackknife method. Weibull function was used to build a simulation model. The simulation model with EVI showed better performance than the model with NDVI. The spring migration was started when EVI values reached about 0.3. Almost all field observation data were observed within the 95% confidence interval of the simulation model output. The simulation model will be used to build a leafhopper migration alert system.</p><br /> <p> </p><br /> <p>Erik Lehnhoff discussed a recently published prediction model for beet leafhopper populations based on November and December rainfall for southern New Mexico. The best correlation was for April 16-30, May 16-31, and June 1-15. The leafhopper numbers for the end of April and May were very good for predicting the total numbers of leafhoppers for the entire system.</p><br /> <p> </p><br /> <p>Bill Wintermantel gave a brief overview of his collaborative research with Bob Gilbertson, UC Davis, to sequence the genome of the beet leafhopper. He has also acquired transcriptome information as it relates to transmission, including different hosts and different time points, and gene pathways. They are developing a draft genome sequence using Oxford Nanopore and are now doing a PacBio long read sequence for a female beet leafhopper because the females are more likely to migrate.</p><br /> <p> </p><br /> <p>Various participants presented field perspectives from different states.</p><br /> <p> </p><br /> <p>Lauren Murphy briefly talked about the CDFA Curly top Control survey and spray efforts for 2020. Spraying of the foothills began early this year in late February in Kings Co. and continued to Fresno in early March, and later than usual in Kern Co. in end of April. There has not been a lot of curly top this year. The late rains may have played a role in the low virus overall.</p><br /> <p> </p><br /> <p>Carl Strausbaugh commented on the unusual weather in Idaho, which included a much wetter and windier May and June, and very focused rainfall. The desert is still quite green and few grasses have even begun to dry down and hopper flights are late.</p><br /> <p> </p><br /> <p>Punya Nachappa talked about collecting leafhoppers from the western slope of Colorado and around Fort Collins. Judith Chiginsky has not found curly top in kochia, but has found it in sugarbeets and hemp. Ana Christina Fulladolsa expects to see symptoms on hemp in late July and August based on last year’s experience. She has not found any correlation of virus symptoms with hemp variety.</p><br /> <p> </p><br /> <p>Carrie Wohleb operates an area-wide insect monitoring system for potatoes in the Coumbia Basin of Washington. In 2020 she found peaks in the beet leafhopper populations June 5 and June 19 in the Hanford Reach National Monument area of south central Washington. She mentioned that curly top has been seen in pinto bean and specialty seed crops such as coriander. Her previous largest leafhopper year was in 2013. 2020 was also an early year for leafhoppers. She had a large number of leafhoppers in August 2019 and a large amount of Russian thistle. She guessed that 2020 will be a moderately bad curly top year.</p><br /> <p> </p><br /> <p>Can we predict leafhoppers populations based on spikes in late fall leafhopper numbers? What factors influence a large fall leafhopper population? Carl found a large number of leafhoppers in Idaho in fall 2019 that correlated with dry down of weeds. However, Idaho had a strong cold snap that likely killed everything in October and little rain afterwards.</p>Publications
<p>No publications reported for this ERA project.</p>Impact Statements
- California field observation data were normalized and then correlated with NDVI and EVI using a Jackknife method. Weibull function was used to build a simulation model. The simulation model with EVI showed better performance than the model with NDVI. The spring migration was started when EVI values reached about 0.3. Almost all field observation data were observed within the 95% confidence interval of the simulation model output. The simulation model will be used to build a leafhopper migration alert system.
Date of Annual Report: 08/13/2021
Report Information
Period the Report Covers: 10/01/2020 - 09/30/2021
Participants
Creamer, Rebecca (creamer@nmsu.edu) - New Mexico State University, Entomology,Plant Pathology and Weed Science
Oliver Neher (oneher@amalsugar.com) – Amalgamated Sugar LLC
Mark Anfinrud (mark.anfinrud@sesvanderhave.com) – SES Vanderhave USA
Tesneem Nusayr (nusayrt@uhv.edu) - University of Houston, Biology
Carl Strausbaugh (carl.strausbaugh@ars.usda.gov) - USDA-ARS, Kimberly, ID
Tiffany McKay-Williams (tmckay@betaseed.com) - Betaseed Inc, Boise, ID
Hyoseok Lee (blueorange23@snu.ac.kr) University of California, Davis, Entomology
Alex Karasev (alexander.karasev@uidaho.edu) University of Idaho, Entomology, Plant
Pathology, and Nematology
Erik Wenninger (erikw@uidaho.edu) University of Idaho, Entomology, Plant Pathology, and
Nematology
Punya Nachappa (punya.nachappa@colostate.edu) Colorado State University, Agricultural
Biology
Thomas Koeps (Thomas.koeps@kws.com) KWS Seed, LLC, Twin Falls, ID
Tyler Yamashita (tyster45@colostate.edu) – Colorado State University
Silvia Rondon (silvia.rondon@oregonstate.edu) Oregon State University
Stephanie Walker (swalker@nmsu.edu) New Mexico State University, Extension Plant Science
Zach Bagley (zach@tomatonet.org) California Tomato Research Institute
Ana Cristina Fulladolsa Palma (ana.fulladolsa_palma@colostate.edu) Agricultural Biology
Imad Eujayl (imad.eujayl@usda.gov) USDA-ARS, Kimberly, ID
Judith Chiginsky (judith.chiginsky@colostate.edu) Colorado State University, Agricultural
Biology
Laura Newhard (laura.nwehard@colostate.edu) – Colorado State University
Marisa Thompson (risi@nmsu.edu) – New Mexico State University, Cooperative Extension
Sam Krasnobrod (Samuel.krasnobrod@cdfa.ca.gov) – California Dept of Food and Ag/BCTV Control Program
Kylie Swisher (kylie.swisher@ars.usda.gov) USDA-ARS, Wapato, WA
Laura Pottorff (laura.pottorff@colostate.edu), Colorado State University, Colorado Seed Programs
Eric Vincill (eric.vincill@usda.gov) - USDA-ARS, Kimberly, ID
Gina Angelella (gina.angelella@usda.gov) USDA-ARS, Wapato, WA
Brief Summary of Minutes
Oliver Neher, Amalgamated Sugar, and host for the meeting welcomed the group to Boise to the Amalgamated Sugar Corporate facilities. Rebecca Creamer, WERA1007 Secretary, explained a bit about the group and its purpose. The group was recently renewed for another 5 years. Introductions were made, and the agenda was discussed.
The new Administrative Advisor for the group is Mary Burrows, Montana State University. She was unable to attend.
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. 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 the changes in timing of leafhopper flights and germination of Kochia from 2008 to the present, and how those might influence management. There was a brief mention of factors affecting virus titer in sugarbeets and how that can be manipulated to develop a virus-free leafhopper colony.
Hyoseok Lee spoke about his research on predicting spring migration time of the beet leafhopper using satellite imagery in California. Every spring beet leafhoppers carrying beet curly top virus (BCTV) are migrating from their overwintering sites (i.e., foothills) to crop fields in the valley floor in California. One of the factors triggering their migration is the vegetation conditions of the foothills. The migration pattern was monitored at the foothills in the San Joaquin valley for three years. We modeled the spring migration pattern based on enhanced vegetation index (EVI) calculated from satellite imagery. As EVI values decrease, more beet leafhoppers start migrating to the valley floor. The migration model is built as an interactive mapping system and will be published via Google Earth Engine.
Carl Strausbaugh reported that screening for resistance to Beet curly top virus (BCTV) in sugar beet suggests that at least some sources of resistance are strain specific. Also, beet leafhopper (BLH) populations can vary by location and year. Thus, at the request of a sugar beet industry stakeholder, BLH populations in southern Idaho were tracked during the 2020 growing season in desert areas and sugar beet and dry bean fields in four southern Idaho counties. Samples were collected on a weekly basis from May through mid-September to assess all leafhoppers for population levels and the presence of BCTV strains. Crop plants from monitored fields were also assessed for the presence of BCTV strains. BLH populations in Elmore Co. were present in at least double-digit numbers through most of the summer at all three sites. However, populations peaked in the Elmore desert (avg. 401 beet leafhoppers per 40 sq. inches) on 20 May, while populations in the bean field peaked in late Jun to mid-Jul (avg. 24) and the sugar beet field on 5 Aug (avg. 69). In the Twin Falls Co. desert, the BLH populations were low (high was an avg. of 3 in Aug) throughout the season. While the Twin Falls Co. sugar beet field peaked with an average of 27 BLH on 22 Jul and the bean field peaked with an average of 4 BLH on 15 Jul. In Minidoka Co. only a few BLH were collected at all three sites late in the summer. In Bingham Co. BLH at the desert and sugar beet sites were almost undetectable through the whole season. However, the Bingham Co. bean field had an average of 23 BLH by 26 Aug. Two haplotypes (based on cytochrome oxidase gene) dominate the BLH population. Over the 19-week collection period, the horizontal card averaged 82% fewer BLH than the vertical card. The BCTV strains found in the BLH population were as follows: Worland (95% of coat protein positive samples), Colorado (22%), Severe (2%), and CA/Logan (1%). The phytoplasma identification is currently a work in progress. Worland was the only BCTV strain found in bean plants. There were 2 BLH samples and 4 sugar beet samples that were positive for coat protein, but negative for the four strain specific primers. Once all data are collected, the project will establish the BCTV strains for which host plant resistance is needed and the best time for when control of beet leafhoppers is necessary.
Samuel Krasnobrod presented the California Department of Food and Agriculture Beet curly top virus control program. The 2021 field season has been characterized by dry conditions and relatively low beet leafhopper activity throughout the San Joaquin Valley. This limited activity resulted in lower-than-average acreage being treated during the spring aerial treatment campaign. As a comparison, 20,150 acres were treated during the spring of 2020, compared to the roughly 6,100 acres treated this year. Curly top virus induced crop damage was recorded across the Central Valley in 2021. This year saw unusually high instances of confirmed curly top damage of tomato crops in Colusa and Yolo Counties. Interestingly, both of these counties are located in the Sacramento Valley, which is further north of the region which typically experiences moderate-to-severe crop damage. Additional beet leafhopper and crop damage surveys will be needed to determine whether or not future curly top virus outbreaks can be expected in the Sacramento Valley. Looking forward, the Beet Curly Top Virus Control Program will continue to monitor these locations in Northern California where confirmed instances of curly top virus damage were recorded.
Marisa Thompson presented mid-season results from field trials looking at effects of row covers and kaolin clay on fresh market tomatoes on curly top and plant growth. She is in year 2 of a covered tomato study at the New Mexico State University Agricultural Science Center at Los Lunas, NM. Treatments include tomatoes covered with either 15% shade cloth or coated in kaolin clay film. The control group is comprised of uncovered tomatoes. All are the indeterminate hybrid ‘Big Beef.’ Along with mortality rates from suspected curly top virus infection, she is comparing midday stem water potential, canopy temperature, photosynthetic rate, yield, fruit quality (e.g., percentage with side-splits and shoulder cracks), and plant size. In year 1, cloth-covered plants were bigger and produced higher quality fruit, but yield differences were not detected, and only four plants died. So far in year 2 (2021), 27.8% of experimental plants have died. As of August 1, 40% of the uncovered control plants, 43% of kaolin clay-coated plants, and 3% of the shade-covered plants were dead. Efforts to formally diagnose plants with the curly top virus versus other possible ailments continue.
At the WERA 1007 meeting, attendees answered questions about testing plant tissues for curly top, curly top transmission concerns, and next steps for future research. Later that week, information was shared with the public via the weekly Southwest Yard & Garden newspaper column titled, “Straight Answers to Curly Questions” (https://nmsudesertblooms.blogspot.com/2021/07/straight-answers-to-curly-questions.html).
Punya Nachappa, in cooperation with Judith Chiginsky, Tyler Yamashita and Laura Newhard, who attended in person presented data on curly top infection of hemp in Colorado. Hemp (Cannabis sativa) production has increased significantly in recent years; however, the crop has been understudied in the U.S. since its production declined in the late 1950s. Disease identification and management is an increasing challenge for hemp growers across the country. Beet curly top virus (BCTV) was first reported in hemp in 2019 from Colorado, the goal of this study was to understand the diversity and prevalence of specific strains of BCTV in hemp. There was a high incidence rate of BCTV (81%) from the 12 counties sampled using species specific primers. All BCTV-positive samples tested positive for BCTV-Worland, BCTV-Colorado or were co-infected with the two strains. A range of symptoms was observed on hemp including yellowing, stunting, curling and twisting. To rule out the presence of other viruses in the hemp samples, shotgun metagenomic analysis was performed on 6 out of 12 hemp samples, revealing 8 viruses and 1 viroid. Phylogenetic analysis revealed BCTV sequences from hemp formed a distinct group along with BCTV-Colorado strains in Genbank. In a separate study, we evaluated resistance in leafhoppers to a neonicotinoid, Poncho Beta and two commonly used pyrethroids, Mustang and Asana. Preliminary results suggest that no resistance to Poncho Beta, but we observed resistance to Mustang and Asana at the labeled rate. The outcomes of this study will inform growers about insecticide resistance in leafhoppers and help growers explore alternate pest management strategies for curly top control.
Ana Cristina Fulladosa Palma presented on developing a seed/seedling certification system for Colorado hemp. There were 20,000 acres of hemp grown in Colorado in 2020. Several groups (Colorado Dept. of Ag., Assoc. of Seed Certifying Agencies, Colorado Seed Growers Assoc., CSU Plant Diagnostic Clinic) are working together to develop a certification process for hemp cuttings or seed derived from a stable mother plant of a specific variety with a unique phenotype. The process currently under development is being expanded to include virus and viroid testing. The steps are: Breeder provides botanical description of a variety that includes physical traits and shows ownership of the variety. The variety will be grown in tissue culture to maintain phenotype. Tissue culture plantlets will be grown in a greenhouse and it and its cuttings will be inspected for compliance with the description and no disease symptoms or arthropod infestation. Both plantlets and cuttings will be sent to the CSU Diagnostic Lab and tested for viruses and viroids, specifically beet curly top virus, tobacco streak virus, and hop latent viroid. If everything passes, the seedlings will be certified.
Various participants presented field perspectives from different states.
Idaho – There have been changes in the hopper numbers at particular locations, some are weather related, but changes have been seen under normal weather conditions. There were also almost no winter annuals during the past year. There have also been changes in the virus strains found in the field. Some of this could be due to the extensive use of neonicitinoids for seed treatment.
California – There was an outbreak of curly top much further north than is usual. There are also still periodic problems with curly top in the Imperial Valley area.
Can we predict leafhoppers populations based on spikes in late fall leafhopper numbers? What factors influence a large fall leafhopper population? Carl found a large number of leafhoppers in Idaho in fall 2019 that correlated with dry down of weeds. However, Idaho had a strong cold snap that likely killed everything in October and little rain afterwards. Rebecca found a very similar trend in New Mexico in fall 2020. Very few leafhoppers in 2021 and very late Kochia emergence.
Research Priorities and Ideas
-Novel genetics for disease resistance and genetic markers for the resistance. Resistance to early infection would be particularly helpful.
- Would like a better understanding of resistance mechanisms, all types.
- How efficacious is malathion for curly top management in California?
- What is the role of acyl sugars in resistance to leafhoppers or leafhopper non-preference?
Punya Nachappa suggested that the WERA1007 group should apply for an SCRI (Specialty Crop Research Initiative) CAP (Coordinated Agriculture Projects) grant for one of the crops that is a problem for curly top, such as peppers, tomatoes, beans or other specialty crops. Christian was supportive of the idea.
There was a brief discussion as to the 2022 meeting location. Punya Nachappa volunteered to host the meeting. The meeting date will tentatively be set for a hybrid meeting (online/in person).