Annual/Termination Reports:

[10/15/2012] [09/19/2013] [07/18/2014] [08/14/2015] [07/25/2016]

Report Information

Participants

Creamer, Rebecca (creamer@nmsu.edu) - New Mexico State University, Entomology,
Plant Pathology and Weed Science;
Bob Hammon (bob.hammon@mesacounty.us)  Mesa County Extension, Colorado State University;
Erik Wenninger (erikw@uidaho.edu) - University of Idaho, Twin Falls;
Carl Strausbaugh (carl.strausbaugh@ars.usda.gov) - USDA-ARS, Kimberly, ID;
Phil Miklas (phil.miklas@ars.usda.gov) - USDA-ARS, Pullman, WA;
Rod Clark (Rodney.clark@cdfa.ca.gov) - Beet curly top virus control program, Fresno, CA;
Bill Wintermantel (Bill.wintermantel@ars.usda.gov) - USDA-ARS, Salinas, CA

Brief Summary of Minutes

No annual meeting was held this year due to time and funding constraints by numerous individuals. Reports on curly top in western states were solicited from previous participants.

Rod Clark, CDFA, sent an extensive report (see full report below) on the curly top virus control program in California. A dry summer and fall produced few beet leafhoppers in the Central and Imperial Valleys. The extreme drought did not support sustained growth of weed hosts of the leafhoppers. Minimal sprays were made to roadside weed hosts. Disease symptoms of curly top were not seen in commercial fields of tomatoes or peppers.

Bill Wintermantel finished up work on Beet severe curly top virus and Beet mild curly top virus. The research project focused on the importance of specific hosts as virus reservoirs that contribute to movement of virus into host crops. He made a video on curly top viruses on tomato, which is available through Plant Management Network at www.plantmanagementnetwork.org/edcenter/seminars/tomato/curlytop/

Phil Miklas does not have any active research projects on curly top virus. For Washington in 2012, curly top incidence in beans has been very low. He is interested in the aspect of major genes and minor genes with broad spectrum resistance against different Geminivirus species such as Bct gene effective against both curly top and bean dwarf pub in Plant Dis 93:645-648. Bct being a dominant gene with linked markers is an attractive set up for candidate gene discovery given the new genomic tools available in bean for which the whole genome sequence was recently released, and large SNP panels will soon be available.

Bob Hammon, Colorado Extension, tested the impact of foliar/soil applications with Scorpion  dinotefuran on tomato.

Erik Wenninger reported a little bit of natural curly top pressure this year on the Kimberly, ID research farm. Only BSCTV and BCTV were found, but not BMCTV, in those plants. He sent a report (see below) of results from a beet leafhopper / curly top insecticide trial carried out by Carl Strausbaugh, Imad Eujayl, and himself last year. This work was part of a publication in Plant Disease that is listed below. They are conducting a similar trial this year that includes more foliar sprays with and without seed treatment; some of the foliars look very promising, but will wait to report on those results. They are also working on developing separate beet leafhopper colonies that have a single virus species or are virus-free in order to examine beet response to individual virus species.

Rebecca Creamer reported a medium low curly top year for southern New Mexico. She has three active curly top projects, one looking at competitive inhibition between curtoviruses, a second studying the role of endosymbionts in leafhopper transmission of curtoviruses, and the third dealing with methods for monitoring leafhopper movement and identification of key weed hosts.

Accomplishments

Collaborative curly top projects for 2012 were carried out between Rebecca Creamer and Robert Gilbertson, and between CDFA (Rod Clark) and Bill Wintermantel.

Publications

Strausbaugh, C.A. and Wenninger, E.J. and Eujayl, Imad A. 2012. Management of Severe Curly Top in Sugar Beet with Insecticides. Plant Disease 96:1159-1164.<br /> <br /> Sedano, M., Lam, N., Escobar, I., Cross, T., Hanson, S. F., and Creamer, R. 2012. Application of vascular puncture for evaluation of curtovirus resistance in chile pepper and tomato. Journal of Phytopathology 160:120-128.<br /> <br /> Wintermantel, W.M. 2012. Curly Top Disease of Tomato. Plant Management Network. Available: http://www.plantmanagementnetwork.org/edcenter/seminars/Tomato/curlytop.

Impact Statements

1. The use of management strategies was assessed, the curly top viruses for particular areas was characterized, and the relationship between viruses and specific hosts.

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Report Information

Participants

Creamer, Rebecca (creamer@nmsu.edu) - New Mexico State University, Entomology,
Plant Pathology and Weed Science; Bill Wintermantel bill.wintermantel@usda.ars.gov) - USDA ARS, Salinas, CA; Alexander Karasev (akarasev@uidaho.edu) - University of Idaho, Dept of Plant Pathology; Li-Fang Chen (lfchen9@gmail.com) - University of California, Davis, Dept of Plant Pathology; Steve Hanson (shanson@nmsu.edu) - New Mexico State University, Entomology, Plant Pathology and Weed Science; Laura Hladky (laura.hladky@ars.usda.gov) - USDA ARS, Salinas, CA; Jorge Achata (jachata@nmsu.edu) New Mexico State University, Molecular Biology; Stephen Peinado (draco134@msn.com) - New Mexico State University, Entomology, Plant
Pathology, and Weed Science; Darryl Bettencourt (dbettencourt@jgboswell.com);
Tom Turini (taturini@ucanr.edu) University of California Extension; Dennis Searle (dsearle@amalsugar.com); John Schorr (jschorr@amalsugar.com); Charles Rivera (chuck@tomatonet.org); Bob Hammon (bob.hammon@mesacounty.us)  Mesa County Extension, Colorado State University

Brief Summary of Minutes

Bill Wintermantel welcomed the group to the Salinas, CA USDA station and 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 work in California. 2013 was the worst year for the disease in tomatoes in the Central Valley of California since the 1990s, even surpassing 2001 in severity. Agriculture in the valley has changed over the past decade, and this may have impacted disease development. Tomatoes are transplanted now instead of direct seeded; there are higher acreages of tomatoes and very few sugarbeets. Curly top levels were very high in mid March in the foothills. The leafhopper distribution, although showing some migration patterns as expected, was much more random and populations were not just found closest to the foothills, suggesting that some leafhoppers may be overwintering in the valley or were moving very early. Weedy fields could be serving as source plants. All plants tested using standard primers for BSCTV and BMCTV, the two species dominating infections in California production for the past two decades, tested positive for BMCTV  including weeds, tomatoes, sugarbeets etc. However, bands were consistently weak, and sequencing suggests a variant that is distinct, but amplifies with BMCTV primers. In contrast, sampling of sugarbeet in Idaho, resulted in a mix of BSCTV and BMCTV. Curly top infection of commercial melon was found for the first time in over a decade.

Bills lab is developing VIGS to induce resistance in tomatoes. The resistance works for at least 35 days. There are initial symptoms, some at 8 days post infection, less at 14 days, and almost none at 24 days post infection. The system includes multiple regions of virus and works against both BSCTV and BMCTV. A patent application has been submitted.

Jorge Achata presented his PhD research looking at mutation rate and mutation hot spots of curly top virus using ion torrent deep sequencing. He presented a discussion of the difficulties with the machine providing high numbers of indels and described the DIs (defective interfering molecules) found.

Alex Karasev gave an overview of curly top in Idaho. BSCTV, BMCTV and BCTV are the most important viruses in the state and sugarbeet and bean are the most important virus hosts. He showed that the disease rating system in sugarbeets does not reflect virus titer using a recombinant antisera to curly top that his group produced. He made infectious clones of BCTV and BSCTV and used both to screen sugarbeet germplasm, finding that some curly top resistant sugarbeet lines were susceptible to the virus derived from the clone, but induced generally lower disease ratings. Alex, working with Imad Eujayl (ARS, Kimberly, ID) has identified some resistant tomatoes and sugarbeet lines. He found that beans were susceptible to virus derived from BSCTV and BCTV clones and that the size of the cloned BSCTV 1.8 genomes was more infectious than the BSCTV 1.2 genomes. He also did tissue printing to localize virus and found it around vascular bundle.

Stephen Peinado presented his MS research on the result of mixed infections of Pepper curly top virus and BSCTV in pepper and sugarbeets. He showed that host influenced whether the viruses competed or reacted synergistically. In sugarbeets, both viruses decreased slightly, while in pepper, PeCTV increased and BSCTV decreased.

Li Fang presented an overview of the current status of curly top virus taxonomy followed by a summary of the disease problems in the Central Valley of CA in 2013. She has monitored leafhoppers for curly top virus titer and strain since 2002. She has found some important recombinants that appear to be stable in the environment, ie. LH71, which has components of PeCTV (rep) and BMCTV/BSCTV (CP), as well as a second emergent variant, pCO95 for which sequence of an isolate was deposited in Genbank many years ago by Drake Stenger. LH71 was common in California during 2013. In severe curly top years, large numbers of leafhoppers are collected early during the year (March) and are found to contain virus. She can use her information on curly top hot spot locations to determine the optimal locations and times to spray insecticide. In March 2013, she found BMCTV and BSCTV in leafhoppers; 84% had BMCTV and 42% had both BMCTV and BSCTV. 63% had strong signal by PCR. Testing tomatoes gave similar results; in Fresno area, around half had BMCTV and half BSCTV, and in Merced 85% was BMCTV. Sequence analysis of limited isolates of the BSCTV determined that much of this was actually the LH71. In contrast to the past 10 years, cucurbits, melons, and watermelon had high levels of infection. She also found eggplant infected for the first time, which had mild symptoms.

Rebecca Creamer presented research on the bacterial endosymbionts of the beet leafhopper. Three different endosymbionts were identified, Sulcia muelleri, an alpha-proteobacter and a beta-proteobacter. The bacteria were all localized to the gut. GroEL was identified and sequenced and shown to be produced by the Sulcia endosymbiont. GroEL was localized to the gut only, while virus could be detected using confocal microscopy to both the head and the gut.

Bob Hammon sent a summary of his results on management of curly top virus in tomatoes in western Colorado.

Carl Strausbaugh sent his poster on the use of Poncho Beta and foliar insecticides in sugarbeets in Idaho. While Poncho Beta-treated seed was very effective in controlling disease in resistant sugarbeet, the addition of foliar insecticides extended the control.

There was an extensive discussion as to the proposed lumping of all curtoviruses into a single species and the renaming of all curtoviruses. The group consensus was that we did not agree with the renaming of the viruses as Beet curly top virus A-H and preferred strain designations which retained the historical and commonly used names. Bill noted that in discussions with Judy Brown, the A-H designations were to be replaced by designations reflecting currently recognized names; however, the group expressed concern that there was not widespread notification that the nomenclature was to be changed and did not as a whole agree with the proposal. Alex Karasev agreed to write a letter to the ICTV expressing the groups concerns.

Research questions concerning curly top research that were raised by the attendees.

" Can functional disease prediction systems be established for southern Idaho and Central Valley of California?
" Sequence of the beet leafhopper would be highly desired.


There was a brief discussion as to the 2014 meeting location and Alex Karasev agreed to host the meeting in Moscow, ID.

Accomplishments

Collaborative curly top projects for 2012-13 were carried out between Rebecca Creamer and Robert Gilbertson (Li-Fang), and among CDFA (Jennifer Willems), Bill Wintermantel, and Robert Gilbertson (Li Fang). Cooperative projects were carried out between Carl Strausbaugh, and Bill Wintermantel and between Carl Strausbaugh and Alex Karasev.

Publications

The group did not publish a report together.

Impact Statements

1. The use of predictive systems and management strategies was assessed, the curly top viruses for particular areas were characterized, and the relationship between viruses and specific hosts was assessed.
2. The group assembled a response to the ICTV on the naming of beet curly top virus strains, which will affect how the virus strains are known within the producer and pesticide industries.

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Report Information

Participants

Creamer, Rebecca (creamer@nmsu.edu) - New Mexico State University, Entomology,
Plant Pathology and Weed Science;
Carl Strausbaugh (carl.strausbaugh@ars.usda.gov) - USDA-ARS, Kimberly, ID;
Alexander Karasev (akarasev@uidaho.edu) - University of Idaho, Dept of Plant Pathology;
Li-Fang Chen (lfchen@ucdavis.edu) - University of California, Davis, Dept of Plant Pathology;
Erik Wenninger (erikw@uidaho.edu) - University of Idaho;
Jennifer Willems (Jennifer.willems@cdfa.ca.gov) - California Dept of Food and Ag/BCTV Control Program;
Trevor Cook (trevor.cook@syngenta.com) - Syngenta;
Josh Reed (josh.reed@ars.usda.gov) - USDA-ARS, Kimberly, ID;
Imad Eujayl (imad.eujayl@ars.usda.gov) - USDA-ARS, Kimberly, ID;
David Elison (delison@amalsugar.com) - Amalgamated Sugar Co.;
Greg Dean (gdean@amalsugar.com) - TASCO/Amalgamated Sugar Co.;
Tamie Keeth (tkeeth@uidaho.edu) - University of Idaho/USDA-ARS, Kimberly, ID;
Tiffany McKay-Williams (tmckay@betaseed.com) - Betaseed Inc.;
Joyce Faler (joyce.faler@ars.usda.gov) - USDA-ARS/Amalgamated Sugar Inc., Kimberly, ID;
Paul Foote (pfoote@amalsugar.com) - Amalgamated Sugar Co.;
Lance Lovell (llovell@amalsugar.com) - Amalgamated Sugar Co.

Brief Summary of Minutes

Carl Strausbaugh welcomed the group to the Kimberly, ID, USDA station and explained a bit about the group and its purpose. Introductions were made, and the agenda was discussed.

Alexander Karasev discussed the molecular tools that his group uses to screen sugarbeet resistance to curly top. BMCTV, BSCTV, and BCTV are the curly top strains generally found in Idaho. Their group approach is to screen for resistance to the three virus strains as well as to leafhoppers Plant resistance is quantitative and difficult to distinguish from leafhopper resistance. To be able to screen for virus resistance separately, they made infectious clones to each of the three different virus strains and infected sugarbeets with one of the clones or added leafhoppers. They made both 1.8mer and 1.2mer constructs for BSCT and BCTV, using similar methods to those of Li-Fang Chen, and used agroinoculation to introduce each construct into Nicotiana benthemiana and into sugarbeet. Early results showed that Monohikari variety sugarbeet was susceptible to all the clones (both 1.8mer and 1.2mers) tested. Sugarbeet variety KDH 13 was resistant to BSCTV and susceptible to BCTV.
Alex also presented work on curly top identified on chile pepper in Delicias, MX (which is south of Chihuahua City within Chihuahua State) in 2010. They showed that 11/94 symptomatic plants contained curly top by ELISA suing the antisera that his lab produced. The cloned and sequenced four of the plants confirmed by ELISA. All were a BMCTV/BMCTV recombinant where the C4 gene is from BSCTV and the rest is BMCTV.

Carl Strausbaugh gave an overview of curly top epidemiology in Idaho and discussed his program of seed and foliar insecticide treatments to control the leafhopper. All of his publications are available at http://eprints.nwisrl.ars.usda.gov/view/cv/Carl_A=2E_Strausbaugh.date.html. There are three leafhopper broods per year in Idaho. The leafhoppers overwinter on mustards in the desert. Initial migration of leafhoppers occurs from May 12 – June 5 with a peak around June 25 in southcentral Idaho.
Carl runs the BSDF Curly Top Nursery where sugarbeet varieties are tested for resistance under severe disease pressure. Disease is rated on a 0-9 scale where 9 is a dead plant. Most varieties have a rating of 4.5-6.8 during the nursery screening. Their ratings are comparable with those from the commercial nurseries.
Carl has extensively tested sugarbeet seed treatments with insecticides. Second generation neonicitinoids provide lengthy consistent protection for at least 59 days after planting. Seed treatment with Poncho Beta will even potentially allow the cultivation of a highly susceptible cultivars. Seed treatment is now mandated for western Colorado. Seed treatment with NipsIT and Cruiser, which are also 2nd generation neonicitinoids show similar efficacy to that of Poncho. Foliar insecticide treatments alone did not work as well as the seed treatments. Scorpion, a neonicitnoid foliar spray, worked, but not for very long, since it is photosensitive. Foliar sprays applied a week before and a week after releasing hoppers in late June were somewhat efficacious, particularly Asana and Mustang, which are pyrethroids. Poncho Beta also helped with control of leafminer reduced populations of black bean aphid, and root aphid (Pemphygus betae), and helped with extended storage of sugarbeet. Not surprisingly, sugarbeet with less curly top virus had better root storage.
Carl also presented data from his curly top species survey. He found that in 2006 Colorado, Idaho, Montana, and Wyoming had BMCTV, BSCTV, mixtures of the two and Idaho also had some BCTV. In 2012 and 2013, Treasure Valley, ID had BMCTV and BCTV, while Magic Valley had only BMCTV. Neither had BSCTV. In 2013, the nursery survey had only BSCTV and BCTV, even though the leafhoppers began with BMCTV also.

Li Fang Chen presented an overview of the current status of curly top virus taxonomy, a summary of the disease problems in the Central Valley of CA in 2013, and her work on characterization of recombinant viruses and symptom determinants in curly top viruses. She has monitored tomato plants and leafhoppers for curly top virus titer and strains since 2003. She has found three important recombinants that appear to be stable in the environment. First, BCTV-PeCT-BV3 was found in CA in tomato in 2009 and it is most closely related to BCTV-PeCT-NM isolate identified in New Mexico. The C4 and C1 ORFs are identical to those of BSCTV, while the rest of genome is similar to BCTV-PeCTV-NM, which is a distinct strain from other known BCTV strains. Second, LH71, identified from leafhoppers collected in California in 2010, has recombinant genome of BSCTV/PeCTV (C4 and C1) and BMCTV (rest of the genome). LH71 is most closely related to BMCTV but remains to be a distinct BCTV strain. Third, BCTV–CO was initially found in Colorado, but several representative isolates identified in California in 2013 are most closely related to BCTV-CO. The recombinant genome of BCTV-CO has C2 and C3 of BCTV-PeCT-BV3 and the rest is BMCTV.
Li-Fang showed the region of C1/C4 gene is the symptom determinant. She made reciprocal mutant of LH71 and showed that mutant with BMCTV C1/C4 region induced symptom phenotype like BMCTV, whereas LH71 contains PeCTV/BSCTV C1/C4 had severe symptom phenotype on N. benthemiana, which was evident as severe stunted growth and vein swelling on tobacco.
In 2013, which as a severe curly top year, large numbers of leafhoppers were collected early during the year (March) and those were found to contain high amount of viruses. Following the virus detection in leafhoppers, Li-Fang detected 96% of ~200 plant samples collected from Central Valley were BCTV positive and further found 65% of those were BMCTV and 77% of those BMCTV-positive samples were the BCTV-CO recombinant. There were 48% of the plant samples contained BSCTV and 65% of those were the LH71 recombinant. Overall the results showed the majority of viruses involved in the curly top disease outbreak in 2013 were the recombinant viruses-BCTV-CO and BCTV-LH71.

Rebecca Creamer presented information on the beet leafhopper and its epidemiology in New Mexico associated with chile pepper. London rocket and Kochia are the key overwintering hosts and oversummering hosts, respectively, in New Mexico. Leafhoppers appear to be able to carry out their entire life cycle on the two plants if there are sufficient fall rains to bring up the winter annuals before the Kochia dies down. Leafhoppers prefer weeds from fallow fields over those from pecans or ditch banks. Larger numbers of leafhoppers were trapped at the margins of fields with abundant nearby weeds than those with smaller numbers of weeds and the leafhoppers were caught on the traps closest to the weedy areas. In fields without high weed pressure, leafhoppers were trapped on different location traps throughout the season. Mapping disease within a chile field, even those close to a weed source, showed a random distribution of infected plants.

Jennifer Willems gave an overview of the curly top problem in California and the control board management system. For updates on BCTV control in California, subscribe to BCTV at http://www.cdfa.ca.gov/subscriptions/. In CA, fialree, peppergrass and plantago are the primary overwintering weed hosts for the leafhopper. Crews conduct sweeps with a sweep net from March-May. If 10-15 adult BLH/10 sweeps are found, then spraying is instituted. Spring insecticide treatments are made with a fixed-winged aircraft using malathion. Spring treatments are timed to kill nymphs before they move into the valley crop land. In June-August, the crews monitor leafhoppers on crop plants and weeds such as Russian thistle, goosefoot, and Bassia. Leafhopper are monitored Sept-November on fallow ground. Malathion is used both in spring and fall using aerial applications. Ground rig treatment applications are supplementary to aerial applications. Both aerial and ground rig applications are timed to knock numbers down prior to the beet leafhopper migrations in spring and fall.
2013 was one of the worst years for the disease in tomatoes in the Central Valley of California since the 1990s. Losses in tomatoes were approximately $100 million. 2013 was a dry mild winter with sporadic rain. There were already high leafhopper nymph counts in January, ~ 70/sweep. Sprays began at the end of March which is somewhat early. Infection of tomatoes occurred from April to harvest, ie. the entire season. There were problems with high numbers of leafhoppers on non-treatable land (for organic cattle production). Endangered species also limits the spray program.
2014 also had a very dry winter and few hoppers were found, and they were on poor hosts such as Atriplex. The salt bush was infected with curly top. They used yellow sticky traps in historical BLH hot spots to get a better handle on leafhopper numbers. Normal hopper counts were found in April, 10-20/10 sweeps. Aerial spraying began April 16. Due to the drought and water restrictions, there are many fallow weedy fields. The program tried several organic products for leafhopper control that could potentially find use in non-treatable areas. While they worked reasonably well- they were applied using a backpack sprayer and could be difficult to gear up for large scale spraying.

There was a brief discussion as to the 2015 meeting location and suggestions were made to hold the meeting in Cody, Wyoming.

Accomplishments

Collaborative curly top projects for 2013-14 were carried out between Rebecca Creamer and Li-Fang Chen (Robert Gilbertson), and among CDFA (Jennifer Willems), Bill Wintermantel, and Li Fang Chen (Robert Gilbertson). Cooperative projects were carried out between Carl Strausbaugh, and Bill Wintermantel and between Carl Strausbaugh and Alex Karasev.

Publications

The group did not publish a report together.

Impact Statements

1. The use of predictive systems and management strategies was assessed.
2. The curly top viruses for particular areas were characterized.
3. The relationship between viruses and specific hosts was assessed.

Back to top

Report Information

Participants

Creamer, Rebecca (creamer@nmsu.edu) - New Mexico State University, Entomology,
Plant Pathology and Weed Science; Alexander Karasev (akarasev@uidaho.edu) - University of Idaho, Dept of Plant Pathology; Li-Fang Chen (lfchen@ucdavis.edu) - University of California, Davis, Dept of Plant Pathology; Erik Wenninger (erikw@uidaho.edu) - University of Idaho; Jennifer Willems (Jennifer.willems@cdfa.ca.gov) - California Dept of Food and Ag/BCTV Control Program; Carrie Wohleb (cwohleb@wsu.edu) - Washington State University, Extension; Bob Gilbertson (rlgilbertson@ucdavis.edu) - University of California, Davis, Dept of Plant Pathology; Sharon Martinez (orion.skywalker@gmail.com) - New Mexico State University, Entomology, Plant Pathology and Weed Science; Lauren Murphy (lauren.murphy@cdfa.ca.gov) - California Dept of Food and Ag/BCTV Control Program; Ozgur Baruman (obatuman@ucdavis.edu) - University of California, Davis, Dept of Plant Pathology; Bill Wintermantel (bill.wintermantel@ars.usda.gov) - USDA-ARS, Salinas, CA; Tesneem Nusayr (tessamn@nmsu.edu) - New Mexico State University, Molecular Biology; Stephanie Walker (swalker@nmsu.edu) - New Mexico State University – Extension Plant Science; Patrick Akers (Patrick.akers@cdfa.ca.gov) - California Dept Food and Ag; Thomas Turini (taturini@ucanr.edu) - University of California, Cooperative Extension, Fresno; Chuck Rivera (chuck@tomatonet.org)- California Tomato Research Institute; Ed Curry (edcurry@vtc.net) - Curry Seed and Chile Co, Pearce, AZ; Phil Villa – Curry Seed and Chile Co., Pearce, AZ

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.

Carrie Wohleb presented the status of curly top and the beet leafhopper in Washington. Important crops that serve as hosts for the virus and hopper include dry beans, snap beans for seed production, crucifers, and sugarbeets for seed production. Watermelons are also produced and are hosts as is coriander grown for seed. She presented her guides for leafhopper identification, including the size (3 mm), and lacking dark spots on the head and wings. The worst curly top years for Washington were 2003 and 2013, however curly top damage is usually localized and can occur any year. The beet leafhopper also transmits beet leafhopper transmitted virescens agent (BLTVA) that causes problems on radish and potatoes (purple top). A survey showed that 9-40% of the leafhoppers carry BLTVA, while 0-50% of the leafhoppers were found to carry beet curly top virus. Common weed hosts of the leafhopper include tumble mustard Kochia, and filaree.

She presented her sampling program for the beet leafhopper on potatoes, which includes trapping with yellow sticky traps from field margins from 45 locations, 2 traps/field, and changing traps weekly. She is using the data to develop a prediction model for disease based on trap catches.

She can use the data to recommend systemic insecticides at planting and foliar insecticides later in the season. She also recommends treating weeds at the margins of fields using rangeland-specific herbicides.

Tom Turini spoke about monitoring tomatoes for virus and leafhoppers in the 2013-2015 seasons in Fresno and Kings Counties of California. 2013 was a very sever curly top year, with some fields with up to 80% incidence in processing tomatoes. 2014 was a low curly top year, while 2105 was an intermediate year with up to 45% curly top in some areas. He is monitoring 23 sites in Fresno, Co. He found the most virus near the coast range, specifically in the Coalinga area or just east of Coalinga.

The cropping system has changed somewhat in that all tomatoes are now started from transplants and the crop has moved from the western side of the Central Valley to the eastern side, to take advantage of more available irrigation water.

He found high levels of BCTV in March planted tomatoes even though most were treated with neonicitinoid insecticides. Most varieties are highly susceptible, so that a specific variety does not contribute much to differences in incidence or symptom expression. Also disease distribution in fields was quite variable.

In his 2015, he found by mid June, 13-34% had BCTV even with Admire at planting. The highest level found was 51% in Firebaugh on 26 June, 2015. In an insecticide trial he found the untreated had 14% disease, Verimark at the high level as a tray drench decreased disease to 5.7%, which Admire added to the transplant water gave 8% disease.

Stephanie Walker discussed curly top disease in New Mexico. She presented the chile production practices, and provided the curly top management recommendations in chile. She also presented on trials for cultural control of curly top in tomatoes, and explained that the crop is primarily for farmers markets, so that organic controls are necessary.

Eric Wenninger presented results from an insecticide trial for curly top in sugarbeet. He compared Poncho Beta as a seed treatment with Asana as a foliar with a combination of both insecticides. The combination significantly reduced curly top. However age-based resistance was very strong, kicking in around 11 weeks after planting, while Poncho Beta lasted until about 10 weeks after planting.

Alex Karasev talked about curly top in Idaho that is a problem on sugarbeets and beans. He reported on testing isolates from the USDA sugarbeet nursery and found CFH, Cal/Logan and Worland strains. He also presented on a BCTV isolate characterized from chile isolated from Chihuahua, Mexico. He found that isolates were recombinants of mild and severe and could be similar to the LH71 isolate that Li Fang Chen had previously reported on.

Bill Wintermantel reported on his testing for curly top strains in tomatoes and sugarbeets in California and Idaho. In 2103, curly top was really bad in Coalinga and the BCTV-CO was the primarily isolate. In sugarbeets in 2003 there were equal amounts of BMCTV and BSCTV, in 2007 all isolates were BSCTV, in 2013 all (and melons) were infected with what appeared initially to be BMCTV, but were similar to Drake Stenger’s (Colorado) CO-95. In Idaho in 2013 there was more BSCTV and lower levels of BMCTV. However what looked like BMCTV was not classic Worland, but instead was a Worland variant that also resembled CO-95, but clearly differed from the emerging variants in California. This supports the premise that new BCTV variants are emerging in California and displacing traditional forms of BCTV.

Bill also reported on competition experiments between different virus strains inoculated by either agroinoculation of infectious clones or leafhoppers. The clone of BMCTV was not as effective, so it was inoculated using 15 leafhoppers/plant. Successful competition experiments compared CFH and BV3 on sugarbeets and tomatoes by adding the same amount of each infectious clone together using agroinoculation.

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.

Tesneem Nusayr presented experiments indicating that the beet leafhopper endosymbionts contain GroEL and that the GroEL from E. coli will nonspecifically bind to virus coat protein. Additional binding experiments are underway.

Li Fang Chen has begun work toward obtaining the genome sequence of the beet leafhopper. Her first experiments were to determine the size of the genome. She used flow cytometry and monitored using propidium iodide-stained nuclei from the heads of the leafhoppers. She found a an average size of 648 MB for female hoppers and 632 MB for males.

Bob Gilbertson gave an update on the analysis of the 2013 curly top outbreak in CA. He explained the survey system and that the outbreak was the result of high populations of leafhoppers and high titer of virus within the leafhoppers, which occurred in 2003 and 2013. With the very large numbers of leafhoppers collected, the hoppers were pooled in groups of up to 30 for testing for BCTV by PCR using strain-specific primer sets. Many weeds were collected and tested for virus also. The most highly prevalent strains were BCTV-CO and BCTV-LH71. Very surprising, but they also found BCTV-SpCT (spinach curly top) in tomato and pepper, which had not been found previously in California. Testing from Imperial Valley, where sugarbeets are still grown, showed that CFH is still predominant in that area.

Bob also talked about efforts to develop/test curly top-resistant tomatoes. They tested tomato varieties that contained the Ty genes, that work against begomoviruses. They crossed the begomovirus-resistant tomatoes with processing tomato lines and found that the F1 lines gave good curly top resistance, but not good marketable qualities. He found that the Ty1 and Ty3 genes are semidominant, the Ty5 gene is recessive, and more recently that the Ty2 gene is semidominant, which explains why the breeding efforts have been so difficult.

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/. Filaree, peppergrass and plantago are the primary overwintering weed hosts for the leafhopper and hopper numbers were slightly high (7-10/10 sweeps) on these plants in January. This triggered a winter spraying at the end of January. Winter spraying has been relatively rare, but was deemed necessary to prevent a repeat of the problems in 2013. Crews conducted sweeps with a sweep net from March-May. When large numbers of adult BLHs 30s-50s/10 sweeps are found the first week of March in Fresno Co., spraying was done within a week. Similarly, spraying was initiated in Kern Co at the end of March. Of the 117 BLH samples collected and the 286 symptomatic tomatoes tested, both were 82% were + for curly top virus.

There were several thoughts about questions that still need to be answered.
Where should yellow sticky traps be place and how do the trap results correlate with sweep net counts?
How does the movement of leafhoppers change with seasons?
What are the landing rates of leafhoppers in different environments and what influences the attractiveness of different plant types and plant distributions?
How far away do the leafhoppers move?
What is the effect of weeds on leafhopper movement?

There was a brief discussion as to the 2016 meeting location and a suggestion was made to hold the meeting in Wyoming if a host could be identified.

Accomplishments

Collaborative curly top projects for 2014-15 were carried out among Li-Fang Chen (Robert Gilbertson), Jennifer Willems (CDFA), Bill Wintermantel, and Tom Turini. Cooperative projects were carried out between Carl Strausbaugh, and Bill Wintermantel and between Carl Strausbaugh and Alex Karasev.

Publications

The group did not publish a report together.

Impact Statements

1. The group has made an impact of curly top in the western U.S. The use of predictive systems and management strategies was assessed, the curly top viruses for particular areas were characterized, and the relationship between viruses and specific hosts was assessed.

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Report Information

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
Mike Green – Wyoming Sugar Company, Worland, WY (307- 347-9801)
Greg Dean – (gdean@amalsugar.com) Amalgamated Sugar Co, Idaho-TASCO, Boise, ID
Oliver Neher (oneher@amalsugar.com) - Amalgamated Sugar Co, Idaho-TASCO, Boise, ID
Brian Schutte (bschutte@nmsu.edu) - New Mexico State University, Entomology,
Plant Pathology and Weed Science
Myron Casdorph – (mcasdorph@wyosugar.com) Wyoming Sugar Company, Worland, WY

Brief Summary of Minutes

Oliver Neher welcomed the group to the Wyoming Sugar office.  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 an emphasis on the situation in New Mexico.  Chile is the most economically important crop host for the virus in New Mexico.  The worst curly top years for the state were 2001, 2003, and 2005, however curly top damage is generally localized and can occur any year.  The most common weed hosts for the beet leafhopper 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.

 

      Allen Poplawsky reported on curly top in southern Idaho from Alex Karasev’s laboratory in which previous work demonstrated mild curly top, Logan and CFH strains on sugarbeets.  He discussed at length testing of beet leafhoppers from the Columbia Basin of Oregon collected 2007-2009.  The beet leafhoppers were removed from sticky traps collected April-November and extracted and tested by PCR. The percentage virus found was 14% in 2007, 25% in 2008, and 17.4% in 2009, for an average virus presence of 18.9%.  The highest levels of virus were found in June, followed by August.  Only the Worland strain of BCTV was found in 2007 and 2009.  After sequencing, the strain found in 2008 was determined to be a Wor/CFH recombinant similar to CO-95, but with slightly different recombination sites.

 

      Tesneem Nusayr reported on her experiments that show that beet leafhopper endosymbionts produce GroEl that differ from other GroEL from other hoppers.  She showed through bacterial 2-hybrid  and beta galactosidase production that the beet leafhopper GroEL binds to the curly top capsid protein, but not stronger or more specific than does GroEL produced by E. coli. There was discussion and interest from the group about the possibility of using this with a transgenic approach to block transmission.

 

Quaid Dobey talked about his research, carried out in conjunction with Brian Schutte and Rebecca Creamer, looking at the temperature 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 is also studying feeding preference of the leafhopper on different sizes of Kochia to determine why the leafhoppers move off of Kochia onto chile, which is a non-preferred host.

 

Carl Strausbaugh reported on sequencing of curly top isolates collected as part of a 2006-2007 survey of infection of curly top in sugarbeets.  He redid the survey in 2012-2015 and characterized those strains.  Overall he found 10 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, CO, LH71, and Kim1 group together in the middle of the phylogram but in different clades.  In 2006, 82% of the samples were infected with Svr (CFH), 100% with Worland-like strains (mainly CO and Wor), and 14% with Cal/Logan.  In 2013, there was 8% Svr, 76% Cal/Logan, and 78% Worland.  In 2014 and 2015 almost all (95-96%) samples were infected with Worland-like strains and very few (0-2%) with Svr (CFH).  Thus the proportion of strains changed over time.  Further analysis of the sequence revealed isoaltes fell into three primary groups which contained further subdivisions: Worland (06/07 and 12-15 subgroups), Svr (ID/OR and MT/WY subgroups), CO (CA, ID/OR, and CO/NE subgroups).

 

      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/.  2013 was a very bad BCTV year for the Central Valley of California.  2016 turned out to be a much lighter year.  There was no fall spray campaign in 2015.  Sprays were done in late March 2016, but rain in April caused further germination of plantago and filaree.  BCTV was at less than 2% statewide in 2016.  However, organic tomatoes continue to be infected at a higher rate.  Summer weed hosts of the beet leafhopper are Russian thistle, Bassia, goosefoot pigweed, while winter hosts are Filaree, peppergrass and plantago.  Kaolin clay sprays were attempted for leafhopper control, but gave mixed results.  It appears that the beet leafhoppers are staying through the winter in the valley instead of all migrating back to the foothills.  Growers are now using sticky traps to get personalized results in addition to the regular efforts of the control board to sweep and spray.

 

      Lauren Murphy reported on control board experiments using organic pesticides to control the beet leafhopper in California.  Three organic insecticies: Azera, Ecotek, and Tritek, were compared with malathion sprays, all at label rates applied using a ground rig.  The tests were done treating Bassia hyssopifolia.  The test was run in the fall.  Pretreatment there were 7-15 beet leafhoppers/10sweeps.  Results were tested at 72 hrs post treatment. Malathion worked substantially better than any of the organic insecticides. However, Ecotec worked the best of those and will be tested again at very high concentrations such as 10 gal/acre. 

 

Greg Dean noted that there has been a natural decrease in beet leafhopper pressure over the last 10-12 years in Idaho.  He speculated that other management strategies might have had an influence on the beet leafhoppers.  The use of insecticide treatment on the seed combined with the frequent use of Roundup to control weeds likely had a positive effect on reducing beet leafhopper numbers.  He speculated that mosquito abatement programs in some areas might also have had a beneficial effect on beet leafhopper numbers.

 

Myron Casdorph noted many of the same trends for Wyoming and said that 2006 was the last bad curly top year for the area.  He noted that flixweed has been the predominant curly top overwintering host for the area.

Accomplishments

<p>Collaborative curly top projects for 2015-16 were carried out among Robert Gilbertson, Jennifer Willems, and Bill Wintermantel,.&nbsp; 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.</p>

Impact Statements

1. The group has made an impact of curly top in the western U.S. The use of predictive systems and management strategies was assessed, the curly top viruses for particular areas were characterized, and the relationship between viruses and specific weed hosts was assessed.

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