Stylet-Oil is a Technical Grade White Mineral Oil used to control certain plant pathogens and insect pests, including powdery mildew, Botrytis bunch rot, mites and whitefly. The oil has excellent eradicant activity against powdery mildew disease and kills mildew spores within seconds of contact. As a protectant, Stylet-Oil protects sprayed foliage and fruit against powdery mildew development from spores which come into contact with oiled surfaces.

Because Stylet-Oil works at the physical level, the quality of spray coverage can affect performance of the product. Spray equipment should be calibrated and main- tained in optimum working order to provide coverage to the point-of-runoff (see Tips on Spraying).

Stylet-Oil has been rigorously tested against powdery mildew on grape (since 1991) and cherry and apple (since 1995). Research trials have been conducted by plant pathologists at the following locations ―

• UC Davis, Davis, California (Dr. Doug Gubler)
• Washington State University, Tree Fruit Research and Education Center, Wenatchee, Washington (Dr. Gary Grove)
• Cornell University, Geneva, New York (Dr. Wayne Wilcox)
• Agriculture & Agri-Food Canada, Ontario, Canada (Dr. John Northover)
• Oregon State University, Corvallis, Oregon (Dr. Jay Pscheidt)
• The Horticulture & Food Research Institute of New Zealand, Ltd. (Dr. Peter M. Wood)

Using Stylet-Oil As An Early-Season
Sulfur Replacement To Control Grape Powdery Mildew

For over 100 years sulfur has been the traditional early-season fungicide used by grape growers for powdery mildew control. Though early-season performance of sulfur often has been  marginal, growers have chosen the material because 1) it is inexpensive and 2) there have been few early-season alternatives.

Sulfur performs marginally early-season because cool weather conditions during the prebloom period prevent volatility of the product. Both the protectant and eradicant properties of sulfur are compromised during cool weather.

The vast majority of any sulfur application is released into the atmosphere as a gas. After sulfur is applied to the plant, sulfur vapors are released. The powdery mildew mycelium produce hydrogen which reacts with the sulfur to form hydrogen sulfide (H₂S ) ― a poisonous gas to the fungus. However, it is this gaseous state that can combine with water in the atmosphere that can result in air pollution or acidic rain. Despite these deficiencies, there have been few alternatives to sulfur ― until now ― for early-season powdery mildew control.

Stylet-Oil Cost Competitive With Sulfur Early-Season
Thanks to a recent price reduction, grape growers now have an alternative to early-season sulfur ― JMS Stylet-Oil or Organic JMS Stylet-Oil. The cost per acre to apply Stylet-Oil is competitive with sulfur when the oil is sprayed between 4 to 6 qts / 100 gals of water in a spray volume of 50 gpa or less.

The early-season program recommends 3 prebloom oil sprays @ 1 to 1.5% spray concentration beginning at budbreak (or 2 to 4-inch shoot growth) sprayed every 10 to 14 days to the point of runoff. An optional 4th oil spray may be made at bloom as a tank mix with either Rovral (1 lb / Acre) or a label rate of Vangard for both powdery mildew and Botrytis control.

During the post bloom period, growers may 1) resume a traditional sulfur program; 2) spray oil alone; 3) tank mix oil with DMI / strobilurin fungicides labeled for powdery mildew control; or, 4) alternate oil sprays with DMI / strobilurin fungicides labeled for powdery mildew control.

Why a "prebloom" Stylet-Oil program? Four good reasons:

First, Stylet-Oil outperforms sulfur as an eradicant. UC Davis plant pathologist Dr. Doug Gubler ranks Stylet-Oil as an eradicant on a scale of 1 to 10 as a "10 versus a 4 for wettable sulfur". Eliminating the early-season primary inoculum can significantly impact secondary infections (which cause epidemics) later in the season.

Second, spraying Stylet-Oil early-season during cool weather periods will not affect efficacy of the product as is the case for sulfur. Cool weather has zero impact on the protectant, eradicant and antisporulant properties of the oil. Stylet-Oil works 24 hours a day against mildew whereas sulfur may not work at all during that same 24 hour period.

Third, Stylet-Oil’s superior eradicant activity should  reduce or eliminate the low population of powdery mildew spores resistant to DMI / strobilurin fungicides. By "cleaning up the vineyard" prior to the first DMI / strobilurin spray, disease resistance management will be enhanced.

Fourth, less than 2% of any Stylet-Oil application has potential to evaporate. (The vast majority of a Stylet-Oil application is degraded by microbes in the environment into carbon dioxide, water and more microbes.)  Almost all of a sulfur application evaporates and can be regarded as a potential air pollutant.

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Spray Program Recommendations

Grapes ― Prebloom For Powdery Mildew

Cherry -- Preharvest For Powdery Mildew Control

Cherry ― Post Harvest Powdery Mildew, Mites

For post harvest powdery mildew, spray 7 to 10 days after harvest @ 1 to 2% spray concentration. Spray to the point of runoff. Used to prevent powdery mildew cleistothecia and thus reduce powdery mildew winter carryover. We recommend the post harvest spray be followed in the spring by one or two oil sprays during the petal fall to pit hardening stage to eradicate / prevent primary inoculum before the first DMI / strobilurin fungicide is applied. This preventative oil program is the basis for a disease resistance management program.

For mites, spray as needed at 1 to 2 % spray concentration every 10 to 14 days. Use higher rate and / or shorter spray interval during heavy mite infestation.

Thorough spray coverage is necessary.

Apple ― Pre Harvest Powdery Mildew, Mites

Vegetables ― Insects, Fungus and Virus

Greenhouse Crops ― Insects, Fungus and Virus

Stylet-Oil is an outstanding product as an integrated pest management tool for control of greenhouse pests. Benefits of using the oil in a greenhouse setting include ―

• insect pest control
• fungal disease control
• soft on beneficials
• low toxicity

A greenhouse setting provides an ideal opportunity to spray Stylet-Oil under optimum spraying conditions. Because the oil is not being applied under adverse field conditions, quality spray coverage can be enhanced  to boost performance of the product. As a result, growers often observe simultaneous control of unrelated pests such as whitefly and powdery mildew.

Insect Pest Control: Stylet-Oil will control a number of greenhouse pests, including whitefly, mite and leafminer. Oil applications will suffocate some adults, however the greatest impact on adult populations will be modification of adult feeding and egg laying behaviors. As such, the oil becomes the primary chemical in an insect pest prevention program. Apply the recommended rate (3 to 6 qts / 100 gal) weekly or every two weeks depending on the level of pest pressure. Spray for thorough coverage.

Fungal Disease Control: Stylet-Oil’s fungicidal properties against powdery mildew and Botrytis make it a powerful tool in a greenhouse environment. Routine weekly or biweekly sprays for insect control usually provide excellent powdery mildew and Botrytis control. Stylet-Oil eradicates active powdery mildew infections and prevents development of mildew and Botrytis on sprayed plant tissue. When spraying for fungal disease control only, use at least 200 psi spray pressure and apply the recommended rate.

Soft on Beneficials: Greenhouse growers spraying Stylet-Oil report little impact on beneficial insect populations ― both predators and parasites. Unlike toxic insecticides, Stylet-Oil applications allow pest / beneficial populations to reach an equilibrium condition. The small population of surviving pests are a food source for reproducing beneficial populations. Stylet-Oil does not significantly affect the specialized host sensing mechanisms used by beneficials to locate their prey. However, if enough oil contacts a beneficial, suffocation can occur. (The tiny spray droplets generated by the spray equipment we recommend for greenhouse application minimize beneficial insect mortality.)

Low Toxicity: The re-entry interval for Stylet-Oil is 4-hours allowing growers a quick return for harvest or maintenance in sprayed areas. Stylet-Oil has no residue tolerance level. In addition, the oil exceeds standards set by the U.S. Food & Drug Administration for "Food Grade Quality" mineral oil (b & c). The unique characteristics of the oil allow growers the option to harvest and market fresh fruit and vegetables as "residue free".

Chemical Compatibility: Growers should read and follow label directions regarding oil compatibility with other chemicals (see Chemical Compatibility). Do not apply wettable or dusting sulfur within 14 days of an oil application. Do not apply micronized sulfur within 10 days of an oil application. Sulfur should never be vaporized in vapor pots while oil is being applied in a greenhouse.

The Need For Quality Spray Coverage: Stylet-Oil works on the basis of physical contact with a disease pathogen, insect pest or host plant spray target. Thus product performance is directly related to the quality of the spray coverage, i.e., the better the coverage, the greater the level of pest control. For insect and aphid-transmitted virus control we recommend the oil be applied at 400 psi spray pressure using ceramic hollow cone nozzles (Albuz ATR lilac color or HCA green color or their equivalent). This spray pressure / nozzle combination will produce tiny spray droplets with enough inertia and turbulence to penetrate to the under leaf surface where many greenhouse pests reside. In addition to enhanced spray coverage, tiny droplets minimize any risk from phytotoxicity from multiple applications under short spray intervals.

Growers who install the proper hardware and follow our spray recommendations generally achieve a high level of success in their control programs. On the other hand, growers who don't use the recommended hardware or choose to ignore our recommendations have seen variable results, including phytotoxicity. For this reason we strongly urge growers to either use the correct spraying hardware while following our recommendations or not to use the product in a greenhouse setting.

Gallonage: Apply in a dilute spray volume from 20 to 100 gpa depending on plant size. Spray to the point of runoff. Vary the volume sprayed by changing the number of nozzles used, not by changing spray pressure, speed of sprayer / dolly or nozzle orifice size. When spraying for fungal disease control only, use at least 200 psi spray pressure. The following equation relates spray coverage to performance ―

50% Spray Coverage = No More Than 50% Kill

Thorough coverage of fruit bunches and foliage is necessary for optimum performance. To enhance thorough spray coverage ―

• maintain a constant tractor / dolly speed
• if necessary, remove excess foliage during the season so the spray can reach fruit bunches
• check nozzles for wear before and during the season. Replace worn nozzles when they eject 10% more gallonage than new nozzles
• spray every row, never alternate rows
• do not apply the oil to wet foliage (spray coverage will be compromised)
• vary the volume of dilute spray according to the size / density of the spray target
• spray to the point of runoff