By Mark Greenspan | Practical Winery & Vineyard
This article does not imply an endorsement of any practice or products from Mark Greenspan or Advanced Viticulture, Inc.
Sulfur has not been applied in the vineyards managed by Jim Cuneo, assistant vineyard manager, during the past eight years. He does not miss it one bit. Cuneo manages the pesticide program on 317 planted acres in the Alexander Valley for Robert Young Vineyards (Geyserville, CA).
A presentation by an agricultural chemical distributor early in 2001 piqued Cuneo's interest in using JMS Stylet-Oil for powdery mildew control. Previously, micronized sulfur was applied at a rate of two pounds per acre per application.
Polaris 6x6 ATV pulls 100-gallon
sprayer in valley floor vineyard.
Cuneo and Jim Young (owner), were interested in reducing or eliminating dusting sulfur to control powdery mildew disease, out of concerns by winemakers of sulfur residues in their grapes. Jim Young set a goal in 2000 to eliminate all dusting sulfur, due to concerns about drift when sulfur-dusting. Not to mention that Cuneo is somewhat sensitive to sulfur as are members of the vineyard-crew. This is a situation that many of us are in, but tend to keep quiet about it, thinking that sulfur is just a fact of life in vineyard management.
JMS Stylet-Oil is a highly refined mineral oil that controls powdery mildew disease by smothering the fungus, Uncinula necator, which causes the disease. The product is very simple - just the oil along with emulsifying materials. There are both organic (listed by the Organic Materials Review Institute) and non-organic formulations of JMS Stylet-Oil. For grapes, it can be applied as a 1% to 2% emulsification with water.
Dr. Doug Gubler, Extension Plant Pathologist at U.C. Davis, has compared Stylet-Oil against sulfur and other chemical fungicides and found Stylet-Oil to be highly effective when used at a 14-day interval at a 2% concentration. Cuneo chose to use it at the lowest recommended concentration (1%) at a rate of 30 gallons of water spray per acre.
"Many oils are registered including OMNI oil and SAF-T-CIDE," says Gubier. "However, even through these work, they have higher phytotoxicity risks. A new product very similar to JMS Stylet-Oil is "Green" that works just as well and is also highly purified."
First trial in 2001
While mineral oil provides an opportunity to reduce or eliminate sulfur application, Robert Young Vineyards has a strict zero-tolerance policy on powdery mildew, so they did not want to take the plunge into mineral oil before testing it. JMS Stylet-Oil was applied in the 2001 growing season in a 20-acre block of Chardonnay, which had a history of being a bit of a problem with regard to powdery mildew.
Robert Young Vineyards began using a two-row 200 gallon ON Target sprayer in 1995. ON-Target spray manifolds produce billions of electrically-charged drops that are attracted to the vines, resulting in excellent coverage and uniformity. Spraying two rows at 15 to 30 gallons per acre allows two to three times more acres to be sprayed in a day. For more information visit www.ontargetspray.com.
"Beginning at budbreak, we applied the material at 14-day intervals, adding copper to the spray tank for the first three passes in the growing season," explains Cuneo. "Copper provides additional mildew control, and helps with frost protection. After the first three applications and up through veraison, JMS Stylet-Oil was mixed with a rotation of systemic demethylation (sterol) inhibitors (DMI's) or maintaining a 14-day application interval."
They have two Adcon weather stations that monitor weather and canopy conditions on the ranch. The data is entered into the UC Davis Powdery Mildew Risk Assessment Model that determines the risk of mildew infection based on the pathogen's reproductive rate. The model allows Cuneo to decide if and for how long to stretch spray intervals. However, Cuneo feels the 14-day interval has worked well as a rule of thumb and that it facilitates manpower and equipment scheduling.
In other vineyard blocks that did not receive oil applications, the fungicides were mixed with elemental (micronized) sulfur materials at 2 pounds per acre, per their standard practice. The result: no mildew problems in the test block. Nor were there any mildew problems in the sulfur-treated blocks, indicating that the mineral oil performed as well as the sulfur did that season.
2002: Expansion to larger acreage
Their positive experience in 2001 led them to expand their no-sulfur program to all of the vineyard acreage at one property on the east side of Alexander Valley. The 67-acre ranch has Merlot, Chardonnay, and Syrah and includes the original 20-acre trial block. It was largely successful that year. there were some powdery mildew outbreaks in many of their vineyards that year, regardless of whether sulfur or mineral oil was applied.
"Outbreaks consisted of a cluster or berry here and there," reports Cuneo, "and an occassional vine where many clusters were infected." Bottom line: JMS Stylet-Oil performed at least as well as the sulfur did in 2002.
Crawler tractor pulls Rears sprayer in hillside
vineyards. All photos by Jim Cuneo.
A lightweight spray rig was purchased to allow all-season access with less soil compaction. They purchased a Rears 100-gallon sprayer (which they generally do not fill completely to reduce the weight). They customized an over-the-row boom to adjust for 6-foot or 8-foot tractor-row spacings. Two of these sprayers are used today, each pulled by a Polaris 6x6 all-terrain vehicle (ATV).
The Rears sprayers can cover two rows in one pass. They are pulled with either a six-wheel Polaris ATV with tracks in valley floor vineyards or with a crawler tractor on hillside vineyards. These sprayers are used up until 18 inches of shoot growth.
They switch to a 200-gallon electrostatic sprayer (for the valley floor vineyards) with On-Target nozzle assemblies, which can be adjusted to spray only the extent of the vine growth at that time of year. the manifolds are adjusted to spray only the extent of foliage and a wider band as shoot growth continues. Cuneo has been very pleased with the coverage that this nozzle arrangement has provided. They began using an On-Target sprayer in 1995 and upgraded the system in 2001.
2003-2005: No more sulfur
Success in their trials led them to expand mineral oil application to the entire vineyard acreage. The previous wettable sulfur and fungicide program was substituted with JMS Stylet-Oil and fungicide applications in 2003.
Cuneo reports a complete success. Not a miracle, mind you; they still have some spot outbreaks of powdery mildew, which they deal with by dropping fruit or by washing with Kaligreen. (In retrospect, the oil could have been used as an eradicant "wash" instead of applying Kaligreen.) But that had been their experience with sulfur also. Net gain: no sulfur drift, no respiratory irritation, and no sulfur residue on the fruit.
Benefits beyond mildew control
While the goal of using mineral oil was control of powdery mildew, the product also has beneficial insecticidal properties. Pacific mites had been a problem in many of their blocks, usually requiring one or two applications of miticide for control. In the 2001 trial block, mites were not a problem where treated with mineral oil and that block required no miticide treatment, unlike some of the sulfur-treated blocks, some of which did require miticide applications.
In the years preceding the trial, agrimek and/or Nexter were needed as applied twice to control mites, 100 acres being treated in 2001 and 30 acres in 2002. In subsequent years, when mineral oil was used in all of their vineyards, it was found that mite populations were much less of a concern compared to previous experiences.
There were some mite hotspots in 2003 and in 2005 (but none in 2004) which required one or two miticide applications. Twelve acres required miticide treatment in 2003 and 50 acres in 2005. But the hotspots were well-defined and the mite infestations less severe than in previous experiences or in comparison to what their neighbors encountered during those same episodes.
Although it appeared that JMS Stylet-Oil seemed to have some suppressive effect on mite populations, they wanted to know if it could be relied upon for that purpose. They tested this by applying mineral oil at a 2% rate on a few mite-infested rows in 2005. To their dismay, it did not suppress the population sufficiently to justify use as a miticide. However, they remain encouraged that it helped to reduce their overall need for miticides in the vineyards.
Another benefit found was that of leafhopper suppression. The mineral oil suppressed populations of leafhoppers, minimizing the need for a pre-harvest application of Provado.
Downside to mineral oil
There are caveats to mineral oil application - sulfur cannot be applied within 14 days of JMS Stylet-Oil application or vice versa, or any potential hot weather that could toast the leaves to a crispy crunch. That is clearly stated on the product's label.
With or without sulfur, spraying in hot weather can cause over-heating and burn of oil-treated foliage. Cuneo's crew begins spraying at midnight and continues until morning in order to apply the material under the coolest conditions. Spraying is halted at 11 am, or earlier if the temperature reaches 800F as a precaution.
Cuneo reports using the lowest recommended concentration (1%) in their spray, and he thinks that the lower concentration helps to avoid heat-related foliar damage. He has seen no foliar damage in their oil-treated vineyards with temperatures into the 90's when spraying is has been halted before 800F is reached.
Another minor downside to mineral oil was that spray volume by electrostatic sprayer increased 50%, from 20 gallons per acre to 30 gallons per acre. This would necessitate more spray-tank refills, but did not seem to be a serious issue to Cuneo. Also, material cost is somewhat higher with mineral oil than sulfur. Cuneo's material costs increased about $1.50/acre per application when changing from micronized sulfur to JMS Stylet-Oil. Growers using a higher rate of sulfur than two lbs per acre will see less of an increase in material cost.
Cuneo mentions another downside to using mineral oil - it tends to coat some of the waxy bloom on berries, giving it the appearance of having water spots. Neither he nor the winemaker are concerned about this cosmetic effect. In his lab, Dr. Gubler found that the presence of residual oil had no negative effects on yeast growth during fermentation.
It appears that, for Jim Cuneo and Robert Young Vineyards, the advantages of using JMS Stylet-Oil for mildew control far outweigh the negatives.
NOTE: While Robert Young Vineyards has shared their positive experience with using JMS Stylet-Oil for powdery mildew control, there is no expressed or implied recommendation for its use. Please conduct your own investigation and experimentation before embarking on a similar program.
Dr. Mark Greenspan is the founder of Advanced Viticulture LLC (Santa Rosa, CA) [www.advancedvit.com] providing consulting services to wineries, winemakers and winegrowers interested in producing premium wine products. He has over two decades of scientific research and viticultural experience, and specializes in irrigation and nutrition management, yield and canopy management, fruit maturation and vineyard technology. He may be contracted at email@example.com or tel: 707-838-3805.
For more information on disease control and fermentation, and sulfur residue and wine quality, readers are invited to pursue the following research published by Dr. Doug Gubler and cooperating researchers:
1. 1997 Dell, K.J., W.D. Gubler, R. Krueger, M. Sanger, and L.J. Bettiga. "The efficacy of JMS Stylet oil on grape powdery mildew and Botrytis bunch rot and effects on fermentation." Am. J. Enol. & Vitic. 49(1): 11-16.
2. 1993 Thomas, C.S., R.B. Boulton, M.W. Silacci, and W.D. Gubler. "The effect of elemental sulfur, yeast strain, and fermentation medium on hydrogen sulfide production during fermentation." Am. J. Enol. & Vitic. 44(2):211-216.