Organic Control of Fungus in Vineyards, Eliminating Chemical Sprays

Final Report for FNC06-608

Project Type: Farmer/Rancher
Funds awarded in 2006: $6,000.00
Projected End Date: 12/31/2008
Region: North Central
State: Ohio
Project Coordinator:
Stephen Pearce
Ohio River Vista Vineyard, Winery & Research Station
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Project Information


The Ohio River Vista Vineyard and Research Station is located in Clermont County, Ohio. This 5.42 acre family farm overlooks the Ohio River as a southwesterly view 200 feet below and six-tenths of a mile distant. The unglaciated soil is rich in clay over limestone underlayment providing suitable drainage. To mitigate erosion, the vineyard rows are terraced east-west, perpendicular to the 30%, steeply-sloped ground. This ideal terroir is capable of supporting 3,000 vines producing as much as 1600 cases of fine wine per year. Vinifera varietals grown include cabernet sauvignon and cabernet franc. French hybrid varietals include traminette and vidal blanc. A field research facility is currently under construction to host faculty and students of nearby universities conducting collaborative projects; this new outbuilding will house processing and laboratory test equipment along with experimental seedling cultivars.

The mature hardwood forest comprising this acreage has been maintained by the family for over 20 years. Trees are not harvested, rather replaced as they fall by new plantings. In spite of their presence causing increased pest pressure on the nearby encompassed grapevines, it is believed that they serve as both windbreak and microclimate moderating influences.

The primary goal of this project was to find out if an artificial environment constructed with clear plastic sheeting could adequately control fungal infections on grapevines, thereby eliminating the need for chemical sprays.

Several secondary goals (not part of the project) were identified for possible future studies. These included comparisons between test and control vines with respect to insect populations, length of growing season, and susceptibility to untimely frost.

1. After preparation of the virgin test plot which comprised removal of mature forest followed by terracing the 30% sloping ground, two-year grafted grapevines were planted 6-foot apart in 7-foot spaced, 90-foot rows. For this study it was important to eliminate as many variables as possible, and using virgin land meant that no prior crops or chemical sprays could be present beforehand.
2. As soon as the vines began to leaf out, 6-mil plastic sheeting was draped over the top wire of test row trellises and extended downward on both sides to within 2-inches above ground level. The sheeting was bound together with binder clips affixed to roughened (by torch melting) edges every 2-feet. Slit (and taped) perforations were made above each trellis post at 30-foot intervals to allow for rising sun-heated air to escape. The primary purpose of this enclosure was to provide a chimney-effect means for the passive circulation of drying air to minimize and hopefully eliminate the growth of fungus. Secondarily the sheeting was intended to minimize contamination by spores of fungal infections and harmful insects from adjacent control vines which were only covered with standard bird/deer netting.
3. Daily inspections of grapevine leaves were made in order to identify as early as possible incipient fungal infections. Although not part of this project, insect scouting was also conducted.
4. A forced-air system was constructed for one enclosed test row to be used in the event that passive air circulation proved insufficient to dry the vines enough to prevent fungal infections.

1. Ron Barrett, Kinkead Ridge winegrower and mentor identified types of fungus infections and encouraged scouting for insects even though these pests were not part of the project. Mr. Barrett remained skeptical throughout the course of the project even as he was supportive of this research effort involving students.
2. Bill Skvarla, Harmony Hill Vineyards, winegrower and mentor, believes the proposed poly-tunnel modification of the draped-sheeting technique might be worthwhile for a small vineyard, but he will continue using fungicides and bird netting.
3. Stephanie Hines, Ohio State Extension agent, reviewed the project and was the main motivator for field day events.

1. Temperatures within the plastic-enclosed vines were found to be 4-12 degrees warmer than ambient on partially cloudy and sunny days. Downy Mildew and Black Rot fungus were both adequately controlled by the plastic-enclosed vines, although the forced-air system had to be engaged during extended 4-day periods of rain whereby the sun could not sufficiently heat the enclosed air to promote passive thermal-siphoning action. Test vines thrived with readily controlled minor infections whereas unprotected control vines experienced serious leaf damage. The difference between infected control vines and unaffected test vines was so apparent that accurate measurements were superfluous. There was virtually no leaf loss from the minor outbreaks of fungi on the protected vines.
2. Unfortunately Powdery Mildew appeared during the second growing season on both control and test vines. The drying action of the plastic enclosure made no difference in the extent of leaf coverage by this fungus. It was noted that the spread of this fungus was much slower within the protective enclosures probably due to the higher temperatures therein. Fortunately the presence of Powdery Mildew did not seem to significantly harm the vines, although the discoloration of harvested fruit would be a drawback for table grape production.
3. One unforeseen negative result was that the 6-foot high by 90-foot long vertical sheeting acted as a giant sail on windy days. Gusts would cause the sheeting to ripple along the row of vines. No visible harm was observed due to this beating of the vines, but it could be a major problem if it occurred during fruit set. On two occasions, greater than 40-mph winds tore the sheeting from the trellis.
4. Another unforeseen result was revealed in the spring of the second growing season. Whereas the plastic sheeting had protected the test vines from harsh winter weather and clearly extended the growing season in the fall, the protected vines were slow to leaf out compared to the control vines. It is believed that the protecting plastic did not allow a gradual winter hardening of the canes necessary for viable growth in the following season. This suggests that removal of the plastic enclosure at harvest must be done.
5. Yet another somewhat negative result was that the 6-mil plastic sheeting proved cumbersome for workers conducting vineyard operations such as pruning and shoot positioning.
6. A very welcome positive result was observed both years, namely the growing season was extended by slightly over 3-weeks for the protected vines. This additional potential ripening period could be used to advantage for grape growers in the North Central and Eastern Regions.
7. One unexpected positive result was that harmful insect pressure was significantly reduced within the sheet-protected rows. The warmer temperature within the test enclosures appeared to favor beneficial spiders while limiting the spread of moth pupae to newer leaves and tendrils found at the top of the canopy.
8. Another unexpected positive result was that the unprotected control vines (which were also not treated with chemicals) did not die in spite of heavy fungal infections which caused leaf death and impairment of vine growth. This suggests that it may be possible for farmers using chemical sprays to reduce preventive scheduled treatments.
9. Because there were no untimely frost occurrences during the two growing seasons, no conclusions can be drawn regarding the efficacy of the plastic enclosures providing protection from frost.

The project was successful because protected grapevines not subject to chemical sprays were only minimally affected by fungal infections. Both Downey Mildew and Black Rot fungi growth can be minimized on grapevines grown within protective plastic enclosures that provide passive as well as forced air drying as needed. Although Powdery Mildew remains a problem, its spread is much slower for such protected grapevines.

On the other hand, because the draped plastic sheeting is subject to tearing in strong winds and cumbersome to handle during daily operations by vineyard workers, it is not recommended for use as per this study. Instead, based on the results of this research, the construction of mid poly-tunnels within which vineyard operations could be carried out is strongly indicated. If the family farm could reduce and even eliminate chemical sprays for true organic grape growing, the many advantages discussed in the grant proposal could be realized, including cost savings, avoidance of exposure to dangerous chemicals by workers, fewer pesticides in water supplies and the food chain, lengthening of the growing season, and mitigation of damage caused by frost and harmful insects.

As outlined on both the accompanying Benefits and Impacts form and the Grant Evaluation form, the elimination or decreased use of pesticides is of direct economic benefit to the farmer. Depending on the type and amount of pesticide use, small farms could save as much as several thousand dollars worth of material and labor. Of further economic, environmental, and social benefits to all is the reduction of the amount of harmful chemicals that end up contaminating water and food supplies.

1. Throughout the duration of the project its purpose was discussed on an ad hoc basis with visitors to the vineyard who asked about the covered rows of vines. The project was briefly announced at one seminar and several winegrower gatherings. The positive outcome of the project resulted in a second field day held at the vineyard which was unexpectedly attended by over three dozen regional farmers.
2. The initial field day was planned for only five participants who were invited by phone and email. A practice field day was then conducted by project student volunteers who brought their classmates. The main (third) field day was announced by postings at two local feed stores as well as the county extension office, but it is believed that the great turnout was principally due to word-of-mouth by project mentors, student workers, and neighbors having previously satisfied their curiosity by both casual and planned visits.
3. Project results were presented at two seminars as well as the three field days and the photo web site ( If accepted by the conference committee, a student poster session will be conducted at the Kentucky Academy of Science annual meeting to be held at Northern Kentucky University this next year.

From this grantee’s perspective, all aspects of the NCR SARE Program are commendable.
Especially of note is the helpful responsiveness of staff to questions. One suggested change that could have eased the financial burden of this project’s cost overruns would be a provision that would allow grantees to apply for additional funding to cover (or match) unforeseen, justifiable expenditures.


Participation Summary
Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.