Recipient Organization
N Y AGRICULTURAL EXPT STATION
(N/A)
GENEVA,NY 14456
Performing Department
(N/A)
Non Technical Summary
Grapevine red blotch virus (GRBV) is of concern to the grape and wine industries in the United States. Consequences of infection include reduction in fruit yield and quality and can cause economic losses ranging between $2,213 to $68,548 per hectare over a 25-year lifespan of a vineyard. The three-cornered alfalfa hopper, Spissistilus festinus, transmits GRBV from grapevine to grapevine in the vineyard but little is known about its phenology and behavior in a vineyard ecosystem. For example, no information is available on preferred feeding and reproductive hosts of S. festinus in vineyards. Information on S. festinus ecology is almost exclusively obtained from legume crops such as soybean, alfalfa, peanuts, which S. festinus is a pest of in the southern U.S. The fact that some legumes like sweet pea, vetch, trefoil, cowpea, and clover are used in vineyard cover crop mixtures hold high precedence in the search for candidates of feeding and reproductive hosts of S. festinus. Plants from the Fabaceae family have previously been collected in the vineyard ecosystem and tested for GRBV. All have tested negative for GRBV, suggesting a limited, if any, role in secondary virus spread (Cieniewicz et al. 2019, Wilson et al. 2020). Nonetheless, removing or tilling these legumes in vineyard settings has been shown to reduce visible populations of S. festinus in the canopy of grapevines (Bick et al. 2020, Wilson et al. 2020). Unfortunately, this practice is not known to reduce the rate of GRBV transmission. Without further guidance and understanding of the interactions between S. festinus and feeding and reproductive hosts, growers continue to implement this labor-intensive strategy, with little to no promise for any benefits with regards to limited disease spread.S. festinus are present in vineyards in Napa Valley, CA during early to mid-summer (Cieniewicz et al. 2018; Wilson et al. 2020). This timeframe does not correspond with optimal disease symptom expression and highest GRBV titer on V. vinifera though, which occurs in October-November (Cieniewicz et al. 2020). Nonetheless, in free-living vines, viral titer is suspected to be earlier, corresponding more closely to the timing of S. festinus' more active months in a vineyard setting. A forest area edging a study vineyard was found to harbor free-living vines infected with GRBV (Perry et al. 2016). This, coupled with the fact that there was significant vineyard edge effect for spread (Cieniewicz et al. 2017; Dalton et al. 2019), makes it quite likely that free-living vines are fed on by S. festinus coming out of diapause and then spreading to the vineyards come June when they begin scouting for reproductive hosts. Determining these virus-vector-host interactions will shape our knowledge of S. festinus ecology and disease epidemiology, which in turn, will inform the development of novel disease management strategies.All in all, the relationship between S. festinus and V. vinifera is unprecedent. The recent discovery of an extended acquisition of 10 days for GRBV to reach the salivary glands of S. festinus (Flasco et al. 2021) and potentially a longer period for transmission to occur, coupled with the confirmation of S. festinus as a vector of epidemiological relevance in the vineyard (Flasco et al. 2023), drives a need for understanding the modality behind the ecology of S. festinus in vineyards more than ever. By using surveillance and scouting methods, alongside S. festinus gut content analyses to track dietary history, plus behavior studies on different grape species, we will study how the ecological community of S. festinus affects the spread of GRBV in vineyards. The findings of this project will provide new insights into the GRBV epidemiology and will be pertinent for providing growers with informed disease management strategies.
Animal Health Component
50%
Research Effort Categories
Basic
50%
Applied
50%
Developmental
(N/A)
Goals / Objectives
The major goals of this project are to advance grapevine red blotch disease ecology by: (i) characterizing the landscape level movement of the three-cornered alfalfa hopper (Spissitilus festinus), the vector of grapevine red blotch virus (GRBV) that causes the disease, in Napa Valley vineyards in California, (ii) determining the ability of free-living vines to serve as a feeding and reproductive host of S. festinus, and (iii) dissemination research progress on disease ecology as well as disease management recommendations to grower communities. This project aims to promote our understanding of red blotch disease epidemiology and vector ecology to improve management strategies through addressing two hypotheses: i.) S. festinus rely on alternative plant hosts other than cultivated grapevines for feeding, reproduction, and overwintering in a vineyard ecosystem, including nearby legumes, weeds, and trees in riparian areas, and ii.) determining if S. festinus use free-living vines within riparian areas, including GRBV-infected vines, as feeding and reproductive hosts. The implications of reproductive and feeding hosts, as well as alternative virus reservoirs, will be communicated to extension personnel and growers for improved disease management in vineyards.The specific objectives of the project are to:Understand the landscape level movement of S. festinus1. Collect and scout for S. festinus in Napa Valley vineyards2. Perform gut content analysis on S. festinusDetermine the ability of free-living vines to serve as a feeding and reproductive host of S. festinus1. Monitor for GRBV and free-living Vitis spp. in the gut of vineyard collected S. festinus specimens2. Perform behavioral and mortality studies of S. festinus on free-living Vitis hosts3. Test the ability of S. festinus to use free-living vines as a primary hostDissemination of information1. Participate at growers' field day meetings and conventions.2. Submit a final reportGrapevine red blotch disease was first described as a threat to grapevines in 2008 on Vitis vinifera 'Cabernet Sauvignon' (Calvi 2011). This disease causes economic losses ranging between $2,213 to $68,548 per hectare over a 25-year lifespan of a vineyard (Ricketts et al. 2017). Grapevine red blotch virus (GRBV) is responsible for the disease (Yepes et al. 2018). Infection results in red or chlorotic blotches on the leaves, decreased bunch weight and yields, delayed fruit ripening, and reduction in sugar and anthocyanin production in berries, all diminishing the quality and marketability of wines made from infected fruits.GRBV affects viticulture across the U.S. (Cieniewicz et al. 2020, Krenz et al. 2014). Once established, grapevines cannot be cured of viral diseases like red blotch, highlighting the importance of preemptive management tactics to prevent virus introduction such as the use of planting stocks derived from certified, virus-tested vines. The only known hosts of GRBV are Vitis spp. such as cultivated grapevines (wine grapes, interspecific hybrids, concord grapes, muscadines, rootstocks), as well as in free-living grapevines such as true V. californica and its hybrids such as V. californica x V. vinifera or V. californica x rootstocks and free-living vines in California (Vitis californica and its hybrids) and Oregon (V. riparia). The primary source of GRBV infection in a vineyard is the use of infected planting materials while short distance, secondary spread in states such as California or Oregon is due to the presence of a flying hemipteran insect. Spissistilus festinus [Say, 1830] (Hemiptera: Membracidae), the three-cornered alfalfa hopper (Cieniewicz et al. 2017, 2018, 2019), transmit GRBV in a circulative non-propagative mode with extended acquisition and inoculation access periods (Flasco et al. 2021). S. festinus vector GRBV from cultivated grapevines (Flasco et al. 2021) to cultivated grapevines, as well as to and from free-living vines (Hoyle et al. 2022).An improved understanding of disease ecology, and virus-vector-host interactions is crucial to implement management strategies aimed at mitigating spread of GRBV in the vineyard. I will study how the ecological community of S. festinus affects the spread of GRBV in vineyards using surveillance and scouting methods, alongside S. festinus gut content analyses. I hypothesize that S. festinus rely on Fabaceae plants, weeds, and trees in nearby riparian areas as feeding, reproductive and overwintering hosts. Additionally, I speculate that free-living vines infected with GRBV in riparian areas are likely a source of virus inoculum.S. festinus is not an economic pest of grapevines, with the only damage caused being from girdling shoots and petioles while feeding. Female S. festinus may oviposit into the green tissues of cultivated grapevines; however, the survival rate of the emerging progeny is minimal and complete mortality is reported by the time they reach their third molt (Preto et al. 2018a). Thus, in a vineyard ecosystem, S. festinus must be relying on alternative plant species for feeding and reproduction, may be vineyard middle-row cover crop species (Preto et al. 2018b). S. festinus is a well recorded pest of alfalfa and soybeans (Moore et al. 1976), and leguminous plants are preferred feeding and reproductive hosts (Preto et al. 2018b). These plants are commonly used within cover crop mixtures in vineyard middle-rows but are also found free-living in non-cultivated edges of vineyards in California, near ditches and reservoirs, along roadsides and in forested areas.The transmission of GRBV to and from free-living vines, and to cultivated grapevines (Hoyle et al. 2022) does not confirm that free-living vines play a role in GRBV spread in the vineyard. To determine if infected free-living vines are playing a role in red blotch disease ecology, an interaction between S. festinus and free-living grapes in a vineyard ecosystem must be identified. In completing transmission assays to assess S. festinus' ability to transmit GRBV, statistical differences were found with regards to the grapevine tissue (Hoyle et al. 2022). Varied rates of transmission were observed depending on the donor and recipient tissue type with a positive association between free-living hybrid vine tissues and transmission efficiency of GRBV by S. festinus (Hoyle et al. 2022). Beyond differences in transmission efficiency, S. festinus also display a more social behavior and survive to adulthood on free-living hybrid vines in comparison to cultivated grapevines. The ability for V. californica and other species of free-living vines to serve as feeding and reproductive hosts of S. festinus should be further documented.In summary, this project will advance our understanding of grapevine red blotch disease ecology and inform disease management recommendations. Research progress will be presented at annual meetings of the American Phytopathological Society and Entomological Society of America, and to grape grower groups, for instance, at Unified Symposium in Sacramento, CA; Sustainable Ag Expo in San Luis Obispo, CA; Cornell Recent Advances in Viticulture and Enology in Ithaca, NY; and Business, Enology, Viticulture New York in Rochester, NY.
Project Methods
The project aims to promote our understanding of red blotch epidemiology and vector ecology to improve management strategies through addressing two hypotheses: i.) S. festinus rely on alternative plant hosts other than cultivated grapevines for feeding, reproduction, and overwintering in a vineyard ecosystem, including nearby legumes, weeds, and trees in riparian areas, and ii.) S. festinus use free-living vines within riparian areas, including GRBV-infected vines, as feeding and reproductive hosts.The project centers on three specific goals and related objectives:To address the first goal and test whether S. festinus rely on alternative plant hosts other than V. vinifera for feeding, reproduction, and overwintering, including nearby legumes and trees in riparian areas, two complementary approaches will be used: i.) Collecting and scouting for S. festinus and legumes in Napa Valley vineyards: Field insect specimens will be collected seasonally for two years from March through October using sweep nets and yellow sticky cards in locations where interactions are expected such as in vineyards and nearby riparian areas. Sticky cards will be placed within vineyard rows as well as in surrounding riparian areas. Sticky cards will be rotated every two weeks and the specimen collection date and sex will be recorded. Because legumes are "preferred hosts" of S. festinus, any observed Fabaceae family plants will be collected, tested for GRBV, and added to the plant DNA library to be used in the gut content analysis. After the first year, additional plant materials relevant to the first year's results will be confirmed and collected for GRBV testing and used for comparative gut content analysis. ii.) Gut content analysis: PCR characterization of plant DNA in the insect gut using specific primer sets and high-throughput sequencing of PCR amplicons will allow us to examine the dietary history of S. festinus throughout the year. To do so, I will use an optimized version of the procedure outlined by Cooper et al. (2019) to PCR amplify the internal transcribed spacer (ITS) DNA situated between the small-subunit and large-subunit ribosomal RNA genes, and the trnL-F intergenic spacer (trnF) of the chloroplast genome, PCR amplicons will be bar coded and sequenced on the Pacific Biosciences platform, Sequences will be analyzed to determine gut contents. Prior to field implementation, insect specimens from bean and alfalfa reared colonies will be used to establish a baseline gut content. The readout of this work will provide a guide to which plant families make up the diet of S. festinus. Statistical analysis based on regression models, mean, standard error, and p-values will be completed for plant species identified at a site specific, landscape specific, and season specific level to identify trends and behaviors in S. festinus dietary histories.To address the second goal and determine if S. festinus use free-living vines within riparian areas, including GRBV-infected vines, as feeding and reproductive hosts, the following three approaches will be used: i.) Monitor for GRBV and free-living Vitis spp. sequences in the gut of vineyard collected specimen: Field specimen insects will be collected as described above. Using multiplex PCR, all specimens will be tested for the presence of GRBV (Krenz et al. 2014). In parallel, red blotch disease incidence will be recorded for their vineyard sites of origin. Further evaluation using gut content analysis will be completed to assess the presence of free-living Vitis species DNA in the specimens' dietary histories. ii.) Behavioral and mortality studies on free-living Vitis hosts: To determine the ability of free-living Vitis species to serve as feeding and reproductive hosts of S. festinus, 10 males and 10 females will be placed on one of three Vitis spp. for two weeks of reproduction in the greenhouse: V. vinifera, V. californica, and V. californica hybrid. This will be done in triplicate for each Vitis spp. Using a scan sampling method during this time, behaviors such as socialness/aggregating, feeding, mating, and roaming will be recorded. Methodology will allow for no constraints on the number of individuals observed, the sampling duration, or of what data or observations will be recorded. Additional variables such as location on the plant and sex will also be recorded. From there, progeny will be monitored for emergence, time between molts and ability to survive to adulthood based on location on the grapevine and type of Vitis. Data will be statistically analyzed based on linear mixed models, mean time, standard error, and p-values. iii.) Ability of S. festinus to use free-living vines as a primary host: S. festinus is believed to overwinter as adults (Preto et al. 2019, Kron et al. 2020). Riparian habitats surrounding vineyards in California contain large, trailing vines of V. californica and V. californica hybrids. To assess whether free-living vines can serve as feeding, reproductive and overwintering hosts of S. festinus, temperature acclimated adults in a one-to-one male to female ratio, will be collected and contained on 20-30 shoots of V. californica hybrids and true V. californica within riparian habitats using insect sleeve cages beginning in October when S. festinus levels in the vineyard are diminished. Shoots will be monitored for oviposition and survival of specimen will be assessed in February of the following year when S. festinus is believed to come out of diapause. Free-living vines have been identified for this work in Napa Valley, California. These vines have been genotyped to determine whether they are true V. californica or V. californica hybrids, their GRBV status is known, and their geospatial coordinates are recorded.To address the third goal and disseminate information, research progress on S. festinus ecology and red blotch disease epidemiology will be communicated to grape growers and extension educators at winter conferences, for instance, at Unified Symposium in Sacramento, CA; Sustainable Ag Expo in San Luis Obispo, CA; Cornell Recent Advances in Viticulture and Enology in Ithaca, NY; and Business, Enology, Viticulture New York in Rochester, NY. Information will also be disseminated to grape grower communities and extension educators via extension articles, and at field days and meetings of regional technical groups, for instance in Napa, Santa Rosa, or Lodi in California. Research progress will also be communicated to the scientific community via presentations at annual meetings of the American Phytopathological Society and Entomological Society of America and papers published in international peer-reviewed journals.Evaluation of efforts and progress will be achieved through weekly lab meetings and frequent individual meetings with the Primary Mentor. The progress of this proposed project will also be monitored by an established, interactive, and engaged advising committee to the PD, which meets as a group annually and individually on a more regular basis. Internal scientific meetings including a weekly graduate student research updates course and semesterly plant virology group meetings at Cornell University will also provide opportunity for review of research progress. Evaluation of efforts and progress will also be achieved by interactions with grape growers and extension personnel throughout the project.