Horticultural Oils (Petroleum Base)
Beyond Pesticides Rating: Toxic
are hydrocarbons used as contact insecticides, acaricides, and ovicides.
Kerosene was the first petroleum oil to be used for insect control in the
early 1900’s. Most horticulture oils used today are petroleum based
(Grossman 1990), yet a growing number of horticulture oils are being made
with vegetable oils, which are considered a least toxic pesticide. Carefully
read the label or ask your pest control service provider to determine if
the horticulture oil is vegetable or petroleum based.
oils are effective in controlling aphids, adelgids, spider mites, mealy
bugs, sawfly larvae, whiteflies, plant bugs, caterpillars, scales, and
some plant diseases like rusts and mildews (Olkowski 1991). They flood
insects breathing pores which lead to prompt asphyxiation and suffocation.
Oils also kills an insect when it touches the outer body, or cuticle, of
an insect leading to dehydration and death of the pest.
oil sprays are formulated with a detergent or soap surfactant in order to
keep the product from separating. Adding soaps to horticulture oil
products also increase the effectiveness of its insecticidal properties.
There are several types of formulations of oils: dormant oils, summer
oils, emulsifiable oils and stock emulsions. Dormant oils are extremely
phytotoxic with varying degrees of susceptibility between varieties and
species. Dormant oils tend to contain a higher level of impurities, but
modern refining techniques have removed a high percentage of phytotoxic
impurities (Grossman 1990).
oils have not been found to lead to insect resistance (Thomson 1983).
of horticulture oils mode of action, they do not pose the high exposure
risk that chemical pesticides do. Horticulture oils have relatively low
mammalian toxicity (Grossman 1990). Petroleum based horticulture oils can
cause skin and eye irritation (Olkowski 1991).
Oils, Vegetable Based
oils that are vegetable based are equally as effective in killing certain
insects as oils that are petroleum based (Grossman 1990). Vegetable based
oils are similar in mode of action, application method, and phytotoxicity.
Vegetable based horticulture oils do not leave residues behind like
petroleum based oils.
J. 1990. “Horticultural Oils: New Summer Uses on Ornamental Plant
Pests.” The IPM Practitioner 12(8): 1-10.
W. 1991. Common-Sense Pest Control: Least-toxic solutions for your
home, garden, pets and community. The Taunton Press. Newtown, CT.
W.T. 1983. Agricultural Chemicals - Book I Insecticides. Thomson