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Funded Project |
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Funding Program:
Regional IPM Competitive Grants - Northeastern |
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Project Title:
Combining a Disease and Weather Monitoring Network with Measurements of Inoculum Potential for Disease Forecasting in Vineyard IPM for Southern New England |
Project Directors (PDs):
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Lead State: CT Lead Organization: Connecticut Agricultural Experiment Station |
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Cooperating State(s):
Massachusetts |
| Extension Funding: $67,411 |
| Research Funding: $61,327 |
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Start Date: Aug-01-2008 End Date: Jul-31-2011 |
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Pests Involved: powdery mildew, fungus, fungi |
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Site/Commodity: grapes, wine |
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Area of Emphasis: weather, monitoring, forecasting, modeling |
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Summary:
This is a Joint Research-Extension project focused on improving control of vineyard diseases while reducing pesticide inputs. This will be accomplished by providing growers via the internet with disease support information on the risk of infection of disease in real time. The system uses weather based disease-risk models. We will establish weather monitoring stations in research and commercial vineyards throughout southern New England. These stations will be connected through cellular modems to a central location. Initial inoculum levels will be directly assayed at test vineyards and the survival and maturation of the over-wintering stage pathogens will be evaluated. In addition, inoculum potential will be evaluated each week using potted trap plants and mechanical spore samplers to determine the concentration of airborne inoculum. Crop growth and disease severity will be assessed each week during the growing season. Trap plants will be sprayed with systemic fungicides to obtain information on the development of fungicide resistant strains in the endemic powdery mildew populations. All disease forecast and recommended management information obtained will be accessible to the growers via the internet. At the end of each season we will report our findings to the growers at an annual meeting.
Objectives: Research Objectives: 1) Improve disease forecasts for grape powdery mildew by including measurements of inoculum density and availability of susceptible host tissue. This will be accomplished by simultaneously measuring the magnitude of powdery mildew inoculum sources, the resulting concentration of airborne inoculum, spore deposition on host tissue, the spore infection efficiency, the expanse and composition of susceptible host tissue, and the resultant increase in disease incidence. 2) Quantify the overwintering survival and maturation of cleistothecia of E. Necator under a range of climatic conditions as part of the inoculum density component of the model. 3) To perform the above evaluations on established research and commercial vineyards, as well as newly planted research vineyards. These test vineyards will span the range of climatic conditions and cultivar selections that mirror the variation found in Southern New England. 4) Use the above results to create a new powdery mildew disease-risk model suitable for the climate of southern New England. This model will provide for the input of fieldbased measures of inoculum potential (cleistothecial counts, and disease severity estimates) and use differential susceptibility of planted grape cultivars to adjust risk levels. Extension Objectives: 1) Provide the grape growers of SNE a web-based information network that provides daily updates of disease-risk information, growing degree days (GDD), and cumulative photosynthetically active radiation (PAR) that is measured within their climatic region. 2) Link the disease-forecast web site to existing web-based IPM resources, and develop new management resources for the site. 3) Help SNE grape growers assess and pest management consultants learn to assess the primary inoculum levels of powdery mildew in their vineyards. This will include late season assays of foliar disease severity and early spring determination of cleisothecial counts on pruned canes and exfoliated bark. 4) Educate growers on the problem of fungicide resistance and visit vineyards having problems controlling powdery mildew to determine whether or not fungicide resistant strains of E. Necator are present in our region. 5) To hold annual meetings to educate growers in use of the grape IPM web site, forecast models, and IPM options for grape disease management, as well as to discuss progress made and report scientific findings that impact disease management strategies. These meetings will also provide a venue for grower feedback and project evaluation. Proposal USDA CRIS research data USDA CRIS extension data |
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Final Report: |
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Outcomes Seven remote-access weather stations were deployed in vineyards throughout southern New England (Fig. 1). Data collected from these weather stations have included soil (20 cm) and air (2m) temperature, rainfall, relative humidity (2m), wind speed and direction (3m), solar insolation, leaf wetness, and soil moisture. The weather stations are located in Hamden CT, New Preston CT, Windsor CT, Colchester CT, Griswold CT, Deerfield MA, and Newport RI. In addition, we accessed data from a weather station at the UMASS farm in Belchertown MA. Cumulative precipitation, growing degree days (GDD) and frost events were recorded/calculated. Disease-risk was calculated from data collected at each weather station using Spectrum Pro Software (Spectrum Technologies, Plainfield, IL). Disease-risk was calculated (see Disease-Risk Attachment) at each location starting 7 May 2009 through 27 September 2011. This information was made available to growers on a weekly basis by direct email messages and through postings on the CAES, UCONN IPM, and UMASS IPM websites. Research vineyards were planted in the spring of 2008 at the three CAES Research Farms, located in Mt. Carmel CT, Windsor CT, and Griswold CT (Figs. 2 & 3). These vineyards are 0.3 A in size and contain three vinifera cultivars (Chardonnay (white), Pinot Noir (black), and Cabernet Franc (black)) and two lambrusca-vinifera hybrids (Vidal Blanc and Chambourcin (black)). Plant material was obtained from the same source and grafted to the same rootstock (Cornell 3309). Each cultivar was planted in 4-vine groups replicated 8 times throughout the plot and trellised in 2009. A second replicate vineyard was planted at Griswold in the spring of 2009 and a trellis was erected in the fall of 2010. Portions of these research vineyards were not sprayed with fungicide to detect the early symptoms of grape pathogens and to test the validity of disease-risk calculations. Winter injury and crown gall have been problematic in establishing these vineyards. Each of the four vineyards has 208 vines (total of 832 vines). Fifty-two vines had to be replaced after the winter of 2008-2009; sixty-seven vines had to be replanted in the spring of 2010. Mortality due to winter injury was most notable in the cultivar Chardonnay (72 plants). Crown gall was especially damaging to the cultivar Vidal Blanc (19 plants). All vines survived the winter of 2010-2011 due to deep snow cover. However, a series of 5 nights in January 2011 with minimum temperatures below -2F at the Griswold site resulted in the death of 90% of the exposed vinifera canes down to the snow line. In the other two experimental vineyards the minimum temperature fell below -2F for only one night and there were fewer dead canes (<10%) as a result. Information on phenology and disease development of grapevines was collected in weekly assays of established Chardonnay located throughout southern New England, including sites in Hamden CT, Windsor CT, Colchester CT, New Preston CT and Newport RI. Data were collected from bud burst to fruit set. The table grape variety Vanessa was also assayed in Hamden CT and Deerfield MA. Research Component: Powdery Mildew Inoculum. For the past four seasons (2008-2011), we have monitored overwintering levels of inoculum of powdery mildew and timing of ascospore release. Primary inoculum was evaluated weekly by extracting chasmothecia from bark, stem, and leaf tissue. Fifty chasmothecia were microscopically examined to evaluate the maturity of the ascospores. The time course of ascospore maturity behaved differently over the 4 years of our observations. In 2008, almost 50% of the isolated chasmothecia released ascospores within a two week period (5/12 - 5/26), which was confirmed by trap plants and suction spore traps sampling the airborne inoculum (see following paragraph). In order to test the effect of climate on the maturation of overwintering inoculum, bark samples were taken in the fall of 2008 from 15-year old Chardonnay grapevines planted at Windsor CT, naturally infested with the grape powdery mildew fungus. These bark samples were divided into four groups placed in mesh bags and overwintered in research vineyards located at Hamden CT, Windsor CT, Belchertown MA and East Wareham MA. In 2009, ascocarp maturation extended over a 5 week period (5/20 - 6/30), and at most 3 out of 50 chasmothecia released ascospores on any one date at all sampled locations. At such low levels of inoculum, statistical analyses of data were problematical due to the preponderance of zero catches. In 2010, bud break occurred in the first two weeks of April and ascospores were trapped from April 30 to late June following each rainfall. In 2011, bud break in the first week of May and ascospores were trapped from May 16 to June 30 following each rainfall. As in 2009, the extended period of ascospore release (8 weeks) was accompanied by low percentages of viable mature chasmothecia. An examination of the weather data indicated that for the last three years (2009-2011), which were characterized by sporadic and extended ascospore release, there were repeated frost and near-frost events after bud break. However, this was not the case for 2008, which had a well defined and synchronized release of primary inoculum. Direct counts of chasmothecia in the fall of 2010 and 2011 indicated that 3-4 times the inoculum was produced on the vinifera cultivars, as compared to the hybrids. Differences in disease resistance should have a major impact on initial disease levels. In addition to direct extraction of chasmothecia from infested plant tissue, we also used trap plants and air samplers to monitor the release of ascospores (Fig. 4). Potted grapevines were exposed in the vineyard for a week at a time and then incubated in a greenhouse (70F) for 7-10 days, after which symptoms of disease were evaluated. This method worked well in the early spring when ambient high temperatures were less than 60F. Under these conditions, powdery mildew colonies on potted plants in the greenhouse developed much faster than infections in the field. However, when high temperatures in the field exceeded 70F for more than a few days, symptoms on plants in the vineyard developed in 5-7 days. This rendered trap plants results useless as predictors of disease-risk and direct field assays of disease were started. Airborne spores were also monitored using air sampling traps. Both the ascospores and conidia of the powdery mildew fungus are haline and difficult to differentiate from other fungal spores when counts are low. In 2010 and 2011, in order to increase the sensitivity of detecting these low levels of airborne inoculum, molecular methods were used to detect the pathogen on the collection surfaces of the spore traps. The polymerase chain reaction (PCR) is a technique that amplifies single or a few copies of DNA across several orders of magnitude, which generates thousands to millions of copies of a particular DNA sequence. Using this technique, it is possible to positively determine the presence of the powdery mildew fungus when as few as 10 conidia or 2 ascospores are present in a sample. Since very low levels of inoculum occur early in the season, the use of this technique enhances our ability to detect the fungus early. Alternate Plant Hosts. In scouting the vicinity of vineyards, we detected powdery mildew on wild grapevines and on a number of alternate host species common to our area: Parthenocissus tricuspidata (Boston Ivy), Parthenocissus quinquefolia (L.) Planch. (Virginia Creeper), and Ampelopsis spp. (Porcelain Berry). Viable chasmothecia were isolated from Virginia Creeper stems and dried Porcelain Berry fruit in the early spring (April-May) of each year of the study, and from Boston Ivy in the Fall of 2010. The identity of the pathogen on these alternate hosts was confirmed by PCR methods as grape powdery mildew. As these plants are outside the vineyards and not sprayed, they can represent a significant source of initial inoculum capable of infecting grapes. Extension Component: Growers received weekly disease-risk reports and monthly GDD reports (see Appendix). These were posted on the CAES, UCONN IPM, and UMASS IPM websites. The phenological information from research vineyards was made available to growers immediately. The first occurrence of disease at each of the monitored vineyards was reported to growers using direct email announcements, accompanied by photographs of disease symptoms (see Figs. 5 & 6), and postings on the above websites. |
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Impacts Research Component: Timing of initial ascospore release was shown to consistently occur 2-3 weeks after bud break. We also demonstrated the effects of early season frost events on the timing and amount of primary inoculum of grape powdery mildew (Erysiphe necator), which reduced inoculum but spread release out over an extended time. A recent study (Moyer, M. M., Gadoury, D. M., Cadle-Davidson, L., Dry, I. B., Magarey, P. A., Wilcox, W. F., and Seem, R. C. 2010. Effects of acute low temperature events on development of Erysiphe necator and susceptibility of Vitis vinifera. Phytopathology 100:1240-1249) also showed the importance of cold temperature on the secondary conidial spread of this disease. These results will be the basis for improved disease risk models for the Northeastern US and in many other northern grape growing regions. While direct examination of chasmothecia, spore trapping and trap plants were each successful in certain years for predicting initial inoculation periods, we demonstrated that PCR-based inoculum detection techniques were consistently more accurate and will better inform IPM practitioners of the optimal timing of critical fungicide sprays. Extension Component: Close observation of unsprayed research vineyards coupled with weather data from CT, MA, and RI allowed us to make timely, early discoveries of unusual disease and warn growers of potential problems, in some cases avoiding significant losses to disease. Examples include: The direct assays of disease on unsprayed grapevines starting in 2009 revealed that the number of grape powdery mildew colonies on the underside of leaves was 3 to 5 times the number appearing on the upper surface. We immediately recommended that growers also examine the underside of leaves when scouting for this disease. This simple change in scouting protocol considerably enhances the ability to detect the presence of the pathogen early in the epidemic. In 2010, there were 3 frost events throughout the region after bud break (28 April, 11 May, and 13 May), which caused considerable yield loss. Reports of frost damage in our research vineyards were posted on the web and a dozen growers contacted us for information on the ramifications of frost damage. The first instance of powdery mildew, in 2010, occurred on unsprayed Chardonnay grapes on 4 June at the research vineyard located in Hamden CT. The unsprayed Chardonnay grapes at the research vineyards located in Windsor CT and Griswold CT did not show symptoms until 10 June 2010 and 18 June 2010, respectively. On 24 June 2010, we found heavy infections of grape anthracnose (Elsinoe ampelina) on berries, leaves, petioles, and young stems of Vidal and Chambourcin at the research vineyard located in Windsor CT. Due to the hot humid weather, anthracnose spread rapidly. The susceptible cultivar "Vidal" suffered 80 % yield loss (Fig. 6). The timely delivery of disease-risk information to IPM practitioners throughout southern New England increased the efficacy of fungicide sprays. Once growers were informed of first outbreak of grape anthracnose at Windsor CT, at least 6 growers scouted their fields for disease. In 2011, the major disease problem was grape downy mildew (causal agent: Plasmopara viticola). Symptoms were first observed on 9 June 2011 on unsprayed Chardonnay vines at the Hamden location. Further scouting revealed that the disease was present at the Griswold and Windsor locations as well. This was 5 - 10 days after flowering when young grape berries are highly susceptible to this disease and a warning was sent out to growers. However, 5 inches of rain fell in the next 6 days making it difficult to get a spray on the vineyard in most locations. The information regarding the presence of downy mildew in our experimental plots resulted in extensive scouting by growers (Fig. 5). Since growers detected disease in the early stages, timely and efficacious fungicide sprays could be applied, which prevented further spread of disease. The ability of alternate hosts to harbor the grape powdery mildew pathogen (Erysiphe necator) has been presented to growers at several meetings in 2010 and 2011. The above information and discussions about the importance of sanitation (removal of alternate hosts) has resulted in a number of growers removing these unsprayed hosts from areas around their vineyards, with the goal of reducing the overwintering inoculum for the next year. |
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