The VVA Winter Technical Meeting was held February 17-19 at the Omni Hotel in Charlottesville, Virginia. Here are some highlights of the research reports presented on Friday.

Doug Pfeiffer and Tim Jordan, Virginia Tech Entomology
Doug Pfeiffer reported on Pierce’s Disease (PD), suggesting that the Tidewater region should continue to monitor for three or more nights below 09.4 C (15 F) for reduced risk of PD; if current trends continue, a high risk season is predicted for eastern Virginia. Mating disruption for Grape Root Borer (GRB) continues, and in response to successful results in our VVA-sponsored research and substantial industry-wide interest, EPA Registration is being sought for a GRB mating disruption product possibly available in 2012.

Preliminary research on brown marmorated stink bug (BMSB) is targeting the biology and management of this emerging pest in Virginia viticulture. Stink bug taint in wine, spray trials at harvest, and improved understanding of general biology are leading research concerns. Lastly, Tim Jordan reported on findings from a statewide surveillance study of grape berry moth (GBM) in Virginia vineyards. Current research is focused on developing a forecasting model to predict and target optimum periods for managing GBM during the growing season. Stink bug taint in wine, spray trials at harvest, and improved understanding of general biology are leading research concerns. Lastly,Tim Jordan reported on findings from a statewide surveillance study of grape berry moth (GBM) in Virginia vineyards. Current research is focused on developing a forecasting modelto predict and target optimum periods for managin GBM during the growing season.

Mizuho Nita, Virginia Tech, Plant Pathology
Documentation of Grapevine leafroll disease in wine grape varieties and native grape species in Virginia, and examination of the movement of the disease for developing management strategies.

Grape Grape leafroll disease is caused by a group of viruses called grape leafroll-associated viruses (GLRaVs). On infected vines, both berry color and sugar contents can be reduced and negatively affect the wine quality. In the severely infected vineyard with a susceptible variety, the crop loss can be up to 30 to 50%. There are several unanswered questions on this important disease.

  • In Virginia, no formal studies have been conducted to see the extent of infection and also which of leafroll-associated viruses are common.
  • Uncertainty of the length of time that the disease requires to spread among vines.
  • Anecdotal evidence of mixed infectionwas shown in previous studies, but no formal study was done to confirm it.

The VA Wine Board and the Viticulture Consortium East have been funding this study.
UPDATES:

  • Over 800 samples were taken from over 140 vineyards and 17 wild grape vines. RT-PCR assay was conducted at Dr. Nayapati’s lab in Washington State University. Although many of virus-infected vines are from pre-90’s planting (=no virus indexing), some newer vines were found to be positive for GLRaVs. Uniform or random spatial pattern is indicating spread by a wind-borne insect (mealybugs) and/or spread by the graft material (i.e., contamination of the vine prior to the planting).
  • Results from a field experiment conducted in Winchester indicated that spread of the virus can happen within the first year of planting if infected vines exist nearby, and the infected young vine may not show visual symptoms. Mealybug populations were observed on newly planted vines, regardless of the treatment.
  • Examination of statistics using >1,600 samples collected in Washington state showed that some of viruses are associated and others are disassociated. Thus there are potential synergistic or antagonistic relationships among these viruses. Also, grouping of viruses by potential vector were observed in the dataset, indicating the importance of vector management.

The other major benefit is the extension activities done along with the survey. I visited more than 70 growers, and most of time, disease management topics beyond leafroll were discussed. In addition, a master’s level student, Mr. Taylor Jones, has joined our lab. We will finish up the survey project in 2011 by adding more samples from both commercial and wild grapes. Also, the assessment of grapevine viruses beyond GLRaVs will be conducted at our lab to confirm the relationship among viruses with VA dataset.

Results from this study will be used to identify vineyards where re-planting is needed; to test other insecticide options for mealybugs management; and to set a guideline for virus screening for clean plant material production.

Other grape pathology researches conducted in my lab are: Development of Map-based grape and apple disease risk assessment system. The project was initiated during the spring of 2010 with funds from the VA Ag council and USDA EIPM program. In collaboration with a team of researchers in VT’s Center for Geographic Sciences (Mr. Peter Sforza and Mr. Seth Peery), and Penn State University’s meteorology (Mr. Paul Knight), we have been developing the infrastructure for the proposed disease risk assessment system. Disease models have been translated into GIS language for map displays, weather data from various weather stations throughout the state were collected, weather data from the national weather service (both observed data and data from weather models) were stored on our computer server, and design of web interface has begun. The next focus on our project is the web-interface and testing of disease models using existing weather datasets.

Detection of common grape trunk/vascular diseases using the real-time quantitative PCR techniques. A study to develop a real-time PCR procedure to detect some of important pathogens of grape trunks and vascular tissue have been proposed to the College of Agriculture and Life Sciences internal competitive grant, and the funds were granted. The ultimate goal of this proposed study is an establishment of a sound nursery practice to minimize the risk of infestation at the nursery level; however, we need to perform a series of preliminary studies prior to the start of more in-depth studies. Thus,
in this study, there are two major objectives toward the goal: 1) Establishment of a modern lab where many of these trunk/vascular pathogens can be diagnosed using newer molecular diagnostic tools; and 2) Examination of grafted grapevines from nurseries.

We are in the process of establishing a protocol for detection of major trunk pathogens in collaboration with Dr. Elwin Stewart of Penn State University: Petri disease (caused by fungi Phaemoniella chlamyspora and Phaeoacremonium species), crown gall (caused by bacteria Agrobacteirum tumefacience and A. vitis), and Bot canker (caused by a fungus Botryosphaeria spp).

Fungicide updates: I also presented fungicide updates and results from fungicide performance trials conducted at Winchester AREC during the 2010 season at the VVA meeting. For more information, please visit my blog http://grapepathology.blogspot.com and click on links to documents on your left-hand side Please give us feedback on this tool.

Peter Sforza, Virginia Tech, Center for Geospatial Information Technology
A new GIS web tool for inspecting vineyard site suitability has been developed at Virginia Tech. This web based tool will allow users to investigate and compile attribute data including soils, climate and topography information for a potential vineyard site. The tool is still in the developmental phase. The tool is available at: http://vmdev.cgit.vt.edu/Vineyards/. Please give us feedback on this tool.

Chris Bergh, Virginia Tech, Entomology
Dr. Chris Berg presented two components of his grape root borer research program. The first component is inspecting the abundance and distribution of grape root borer in Virginia. This information can be used to clarify the environmental and horticultural factors that influence the distribution of grape root borer. The second component of this project inspects the efficacy of different trap types on grape root borers. The influence of trap type, color and aperture on efficacy in trapping grape root borer has been inspected and reported. This information will be helpful for the development of mass trapping protocols. Both components of grape root borer research will continue into the 2011 growing season.

Lynn Rallos and Anton Baudoin, Virginia Tech, Plant Pathology
The next presentation described experiments with “sentinel vines,” potted grapevines sprayed with low rates of individual fungicides to determine the sensitivity of a powdery (or downy) mildew population to those fungicides, and how results with sentinel vines compared to those of field trials. Also briefly reviewed were a study on the stability of strobilurin resistance when use of those fungicides is discontinued, and new cases of fungicide resistance in other regions or crops that could shed light on what eastern US grape producers may face next.

Molly Kelly, Virginia Tech, Food Science and Technology
This research project involves characterizing regional Petit Manseng grape and wine volatiles and aroma precursors. This variety shows substantial potential for the VA and NC wine industry. The characterization of the aroma profile of Petit Manseng wines from the mid-Atlantic region will provide insight into regional similarities or variations. Once the characterization of the aroma profile is complete, sensory “profile maps” will be created demonstrating how regional wines differ from each other and thus provide information regarding the sensory uniqueness of NC and VA Petit Manseng. Once the specific sensory attributes that drive consumer likes or dislikes are understood, more informed production, winemaking and marketing decisions can be made.