Vegetable Oils

Vegetable oils also can be used as insecticides, although the type of oil can greatly affect its activity. Cottonseed oil is generally considered the most insecticidal of the vegetable oils. Soybean oil and Canola has often provided fair to good control of some insects and mites.

Oils also can be mixed with other insecticides, providing a broader spectrum and greater persistence of control. Spider mites, whiteflies and young stages of scales are common pests that can be controlled by oils during the growing season. Oils are sometimes applied to prevent transmission of viruses. Many viruses spread by aphids (nonpersistent viruses), as well as some that are mechanically transmitted by people, can be inhibited by oil applications. Oils also are useful against powdery mildew. Diluted horticultural oils, often mixed with a small amount of baking soda, can be an effective control for this common plant disease.


The following precautions are recommended whenever using an oil on a woody plant:

  1. Do not apply when temperatures are excessively high (above 100 degrees F) or low (below freezing). High temperature limitations are primarily related to the drought-stress status of the plant. Plants under stress may be damaged. Those not stressed are much less likely to be damaged by an oil application. Dry conditions without plant stress generally reduce risk of injury by oil, because evaporation is more rapid.
  2. Do not apply oils in combination with sulfur or sulfur-containing pesticides such as Captan or Karathane. They can react with oils to form phytotoxic compounds. Because elemental sulfur can persist for long periods, label directions on most oils prohibit their use within 30 days of a sulfur application.
  3. Do not spray oils in direct sunlight, it will burn plants. It recommended spraying in the evening time or when the light cycle ends.
  4. Plants sprayed under drought stress may have increased risk of injury. Make sure all plants are watered before spraying.

Insect Control: Horticultural Oils, Colorado State University

Texas A&M AgriLife Extension Service

EPA - Flower and Vegetable Oils


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Cottonseed Oil

Cottonseed oil is a cooking oil extracted from the seeds of cotton plants of various species. In an agricultural context, the toxicity of untreated cottonseed oil may be considered beneficial. Oils, including vegetable oils, have been used for centuries to control insect and mite pests. This oil has been generally considered the most insecticidal of vegetable oils.

Target Pests:  Most commonly used against mites, aphids, whiteflies, thrips, mealybugs and scale insects.

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Soybean Oil

Soybean oil was first registered in 1959 for use as an insecticide and miticide. Three products currently are registered. They are emulsifiable concentrate formulations used to control insects and mites on citrus fruits and a variety of ornamentals.

Target Pests:  Most commonly used against mites, aphids, whiteflies, thrips, mealybugs and scale insects.

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Canola Oil

“Canola” isn’t a plant. It’s a Canadian Canola Association registered trademark for oil derived from oilseed rape plants. Most of the world’s canola oil needs are supplied by two species of oilseed rape, Brassica napus L. and B. rapa LL.

Target Pests:  Most commonly used against mites, aphids, whiteflies, thrips, mealybugs and scale insects.