Resource Guide for Organic Insect and Disease ... - Cornell University

MATERIAL FACT SHEET
Oils
MATERIAL NAME: Oils
ACTIVE INGREDIENT NAME: Petroleum (mineral), fish, plant, and essential 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:
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 may 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 (NOP 2000).
ACTIVE INGREDIENT DESCRIPTION:
Three types of related 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, higher purity 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 are composed of 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 n.d). Oils with median boiling points (i.e.,
the distillation midpoint or the point at which 50 percent of the oil has distilled) of 415-440
°F are not phytotoxic, yet persist long enough to smother pests. Oils with a high percentage
of constituents whose boiling points are 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
& 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 & 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 their
Organic Resource Guide 143