Material Name: Oils

Active ingredient name: Petroleum (mineral), fish, and plant oils. See the Neem chapter of this guide for information on neem oil.

Active ingredient type: synthetic and natural oils

U.S. EPA toxicity Category: III, "Caution"

USDA -NOP status:
Certain fractions of petroleum oils (narrow range oils) are considered synthetic and allowed for insect, mite, and disease control. “Narrow-range oils” are highly refined petroleum oils with a median boiling point from 415-440 °F under controlled vacuum conditions. They are allowed for both dormant and growing season uses for insect or disease control. Allowed oils can also be derived from vegetable and fish sources. Approved products must also not contain any prohibited inert components. Preventive, cultural, mechanical and physical methods must be the first choice for pest control, and conditions for use of a botanical or synthetic material permitted on the National List must be documented in the organic system plan (7CFR 205.206(e)).

Active ingredient description:
Three related but different types of oil products are discussed here. Petroleum oils (sometimes called mineral oils) have a long history in crop protection. The first recorded use of oils for pest control was in 1865 when a petroleum distillate (kerosene) was used against scale insects on orange (Agnello 2002). In the 1990’s, the availability of highly refined, lighter weight, lower impurity oils with sunscreens to reduce phytotoxicity extended the use of mineral oil products to control pests on crops in full foliage. These are often referred to as “summer weight oils” or “light weight horticultural oils”. There are well-defined standards for the composition, phytotoxicity, and pesticidal activity of petroleum oils (Agnello 2002).

Petroleum oils are derived from crude oil, which is separated into fractions by heat in a distillation tower. Different fractions represent different hydrocarbons of various weights, structures and boiling points and each fraction may have different pesticidal properties. The term, “narrow range oils” refers to the fact that these approved spray oils are highly refined and relatively homogeneous. The range of boiling points for their constituents is relatively narrow. It is measured as the 10 to 90 percent distillation range (the measurements at which 10 percent and 90 percent of the oil has distilled). Spray oils should have a 10 to 90 percent distillation range of 80°F or less. The narrower this distillation range, the more predictably the spray oil will perform on pests and plants (Whitmire). Oils with median boiling points of 415-440 °F (also known as the distillation midpoint, the point at which 50 percent of the oil has distilled) are not phytotoxic; yet persist long enough to smother pests. Oils with a high percentage of constituents whose boiling point is above 455 °F tend to be phytotoxic (Davidson et al. 1991). Spray oils with midpoints below 400 °F have poor pesticidal activity. Petroleum oils are variable depending on the geographic source of the oil.

Plant and fish oils are chemically classified as lipids containing long-chain hydrocarbons (Sams and Deyton 2002). Lipids include fatty acids, some alcohols, glycerides, and sterols. The chemical and physical properties of plant and fish-derived spray oils are determined largely by the structure of the fatty acids. The fatty acids most commonly found in plant oils are palmitic, steric, linoleic and oleic acids (Sams and Deyton 2002). Plant oils are primarily derived from seeds (e.g. soy and canola) while fish oils are by-products of the fish processing industry. Although there is interest in using botanical and fish oils as pesticides, one of the factors limiting the use is the variability in oil composition and the absence of well-defined standards for pesticidal usage (Sams and Deyton 2002).

Another category of products currently available includes mixtures of essential plant oils, such as wintergreen, clove and rosemary. These are generally pressed from leaves, stems, and/or flowers rather than seeds. They may be formulated with mineral oil in products which claim to be effective for insect, disease and weed control. Some are exempt from EPA labeling requirements (see Appendix F). Little information is available at present regarding mode of action or efficacy for these products.

How it works
Petroleum oils are widely used to control the egg stage of various mites and insects by preventing the normal exchange of gases through the egg surface or interfering with the egg structure. When used against other stages of insects and mites, the oils can block the respiratory system causing suffocation or break down the outside tissue (cuticle) of the insect or mite. Secondary toxicity mechanisms include penetrating arthropod tissues and degrading them, and fumigant effects of volatile oil components (Taverner 2002). Oils may also repel some pests (Stansly et al. 2002). Plant and fish-derived oils probably have similar modes of action. Oils derived from all sources may also alter the behavior of insects and mites and cause them to avoid laying eggs or disrupt their feeding. Additional work in this area is needed to determine which fractions may cause this behavior and to what extent such changes in behavior may affect pest management.

Besides direct control of insects and mites, oils may also provide some control of insect-vectored plant viruses. Stylet oils are derived from petroleum and, when sprayed on plants, inhibit the ability of aphids to acquire the virus in the plant and transmit it to other plants (Davidson et al. 1991). It is thought that oils interfere with the retention of virus organisms on insect stylets (Wang and Pirone 1996).

Both petroleum and plant oils suppress some fungal diseases, especially powdery mildew. The mechanism for this is not clear, but may involve disruption of fungal membranes or interference with spore attachment or germination. Oils may also increase host plant resistance response (Northover and Timmer 2002).

Oils are often added to other pesticide products to improve efficacy. In this sense, they are considered spray adjuvants, even though they may have pesticidal activity on their own.

An application of fish oil is as a thinner in organic fruit production, sometimes in conjunction with lime sulfur. Evidently, it works partially by suppressing photosynthesis. This indicates that crop yield should be examined in studies of fish oil and perhaps other oil products. Mineral and soybean oils have been shown to delay bloom and thin the crop in peaches, most likely by suppressing respiration (Sams et al. 2002).

Types of pests it controls
Oil products can control a wide range of soft-bodied insects such as aphids, mites, thrips, whiteflies, mealybugs, and psyllids. In the 1940’s, highly refined “white” oils were widely used to control corn earworm (Barber 1944). The “Zea-later” is a new tool marketed today for the application of a mix of plant oil and Bt directly into the silk channel of corn to control the corn earworm (see Hazzard and Westgate 2004).

Sams and Deyton (2002) state that oils are “the only widely used class of pesticides to which insects or mites have not developed resistance.”

Formulation and application guidelines:
Pure oils need emulsifiers to stay in suspension when they are mixed with water. Most oil products have an emulsifier already added. Detergents or surfactants may also be added to oil sprays, or incorporated into oil products. These may show some pest control efficacy themselves, though they are usually considered to be inert adjuvants (Stansly et al. 2002).
Good coverage is important. Several applications may be needed for full control of some pests.

Phytotoxicity can be a problem. It can show up as visible leaf damage, or more subtly as yield reduction. In one study, while bi-weekly oil applications reduced whitefly counts on tomato leaves by two thirds, yield on the oil-treated plants was also reduced compared to untreated plants (Stansly et al. 2002). In another case, five oil sprays controlled powdery mildew in grapes but reduced sugar levels (Northover 2002).

Follow label recommendations to minimize phytotoxicity. The slower the oil evaporates, the higher the chance of phytotoxicity. Oil applications are not recommended on very humid days for this reason. Some crop varieties may be extra-sensitive. Oils are incompatible with sulfur and copper on some crops.

In order to avoid phytotoxicity on apples, VanBuskirk et al. (2002) recommend:
• Use oil in a dilute application (with a minimum of 200 gallons/acre on apples)
• Do not exceed an oil concentration of 1% (volume to volume)
• Do not apply when temperatures exceed 80 degrees F
• Avoid large droplets
• Ensure good tank agitation
• Make sure oil is completely emulsified

An oil product that makes a pesticide claim must be a registered pesticide, or in the case of certain essential oils, it may qualify as a pesticide that is exempt from registration. Other oil products are sold as stand-alone adjuvants, for use in tank mixes with registered pesticide products. Adjuvants do not have to be registered with EPA, though a few states require registration. Be sure to follow label instructions in all cases.

Availability and sources

OMRI listed products:

Petroleum oils:

JMS Stylet Oil (JMS Flower Farms, Inc.)
PureSpray™ Green (Petro Canada)

Plant oils:

Concern® Pesticide Spray Oil (Woodstream Corp.)
GC-3, GC-Mite (JH Biotech, Inc.)
Carrier™ (adjuvant) (Stoller Enterprises)
Eco E-rase (IJO Products, LLC)
Golden Pest Spray Oil (Stoller Enterprises)
Green Cypress Organic Spreader (Monterey Chemical, Co.)
Lilly Miller Vegol Growing Season Spray Oil (W Neudorff GmbH KG)
Natur’l Oil (adjuvant) (Stoller Enterprises)
Vegol (W Neudorff GmbH KG)

Fish based oils

Oleum Alimentos Concentrados California SA de CV
Feed-N-Gro Sea Cide (Fertrell Co.)
Organocide (Organic Laboratories, Inc)
SeaCide (Omega Protein, Inc)

References to OMRI listed products in this Guide are based on the June 2004 edition of the OMRI Brand Name List. Please consult www.omri.org for changes and updates in the brand name product listings.

Reentry interval (REI) and pre-harvest interval (PHI):
Stylet Oil: REI 4 hrs, pre-harvest interval: 0, Golden Pest Spray oil (soy bean oil)- REI 12 hrs.

Effects on the environment:
Petroleum oils used on plants are light weight and generally evaporate quickly. The environmental effects of oil vapors are not known. Oils have negligible ability to contaminate soil or groundwater. Plant and fish oils are not as volatile, but they are broken down quickly by microbes on leaf surfaces and in the soil. They are unlikely to have any effect on wildlife or other non-target species (Ebbon 2002).

Effect on natural enemies:
Oils can kill beneficial mites and cause flare-ups in pest mite populations, as happened in one grape field study (Walsh et al. 2000). Oils are unlikely to have a major effect on most beneficial species unless they are exposed to direct spray cover. Eggs and immatures are generally more susceptible to oil than adults.

Effects on human health:
It is unlikely that any measurable oil residues from field spraying remain on crops at time of harvest, so consumer exposure is very small. Most oils are of low toxicity to workers mixing sprays.

Efficacy
Oils have a long history of effective use on fruit trees, but have not been used as extensively in vegetables and other crops. Oils are generally used against mite and scale pests, particularly in dormant sprays on fruit crops. However, lightweight horticultural oils can also be used during the season on fruit with little if any phytotoxic damage.

It is likely that the addition of oil products can improve the efficacy of other organically approved pesticides, though product combinations are not included in this review. For instance, combining oil and potassium bicarbonate is thought to produce better anti-fungal results than either substance alone.

Against vegetable insect pests, oil products have been only partially effective, except for a good result in one trial against pest mites. On fruit crops, oils have shown some good results against mites, San Jose scale, and spotted tentiform leafminers. They have had fair success against pear psylla and caterpillar pests, and controlled powdery mildew well on stone fruit crops. In general, oil products were not very effective against powdery mildew diseases on other crops in these trials.

Below is a chart comparing the efficacy of different products used in the other three charts above. Since some pests showed poor results no matter which products were used, results against these pests are not included. Since the trials represented in this product comparison were conducted against different pests under different conditions, they are not strictly comparable and this comparison should not be viewed as conclusive. Nevertheless, it is worth noting that the organically approved products performed relatively well.

Product types:
Petroleum oils:
Biocover, Damoil, Omni Oil, Orchex, Safe-t-Cide, Stylet Oil, Sunspray, Volck Supreme
Plant oils:
Cottonseed oil, soybean oil
Mixture:
Hexacide (wintergreen, rosemary, mineral oil), DR-A-34 (experimental)

References
Agnello, A. 2002. Petroleum-derived spray oils: chemistry, history, refining and formulation. pp 2-18 In Spray Oils Beyond 2000 (edited by G. Beattie et al.). Univ. of Western Sydney Press.

Barber, G. W. 1944. Mineral oils, alone or combined with insecticides, for control of corn earworms in sweet corn. USDA Technical Bulletin 880.

Davidson, N. A., J. E. Dibble, M. L. Flint, P. J. Marer, and A Guye. 1991. Managing Insects and Mites with Spray Oils. University of California Division of Agriculture and Natural Resources Publication 3347.

Ebbon, G. P. 2002. Environmental and health aspects of agricultural spray oils. pp. 232-246 In Spray Oils Beyond 2000 (edited by G. Beattie et al.). Univ. of Western Sydney Press.

Frear, D. E. H. 1955. Chemistry of Pesticides, 3rd ed. Van Nostrand Co., New York.

Hazzard, R. and P. Westgate. 2004. Organic Insect Management in Sweet Corn. U. of Massachusetts Extension Vegetable Program.
http://www.umassvegetable.org/soil_crop_pest_mgt/articles_html/organic_insect_management_in_sweet_corn.html

Northover, J. 2002. Optimum timing of Stylet oil for control of powdery mildew and European red mite without affecting juice sugars in Canadian grapes. pp. 402-408 In Spray Oils Beyond 2000 (edited by G. Beattie et al.). Univ. of Western Sydney Press.

Northover, J. and L. W. Timmer. 2002. Control of plant diseases with petroleum and plant-derived oils. Pp. 512-526 In Spray Oils Beyond 2000 (edited by G. Beattie et al.). Univ. of Western Sydney Press.

Sams, C. and D. Deyton. 2002. Botanical and fish oils: history, chemistry, refining, formulating and current uses. pp 19-28 In Spray Oils Beyond 2000 (edited by G. Beattie et al.). Univ. of Western Sydney Press.

Stansly, P. A., T. X. Liu, and D. J. Schuster. 2002. Effects of horticultural mineral oils on a polyphagous whitefly, its plant hosts and its natural enemies. pp. 120-133 In Spray Oils Beyond 2000 (edited by G. Beattie et al.). Univ. of Western Sydney Press.

Taverner, P. 2002. Drowning or just waving? A perspective on the ways petroleum-based oils kill arthropod pests of plants. pp. 78-87 In Spray Oils Beyond 2000 (edited by G. Beattie et al.). Univ. of Western Sydney Press.

VanBuskirk, P., R. Hilton, and H. Reidl. 2002. Use of horticultural mineral oil for suppression of codling moth and secondary arthropod pests in an area wide mating disruption program. pp. 356-361 In Spray Oils Beyond 2000 (edited by G. Beattie et al.). Univ. of Western Sydney Press.

Walsh, D., R. Wight and M. Olmstead. 2000. Acaricide efficacy and effects on twospotted spider mites in Washington State wine grapes, 1999. Arthropod Mgt. Tests 29: C14.

Wang, R. Y. and T. P. Pirone. 1996. Mineral oil interferes with retention of tobacco etch potyvirus in the stylets of Myzus persicae. Phytopathology 86: 820-823.

Whitmire Micro-Gen Research Laboratories, Inc. Technical information, Ultra-Fine Spray Oil. http://www.wmmg.com/pdf/pmb/PMB-UltraFineOil.pdf