Horticultural Oil Guide

Last Updated December 15, 2020 By Bella Zinti

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Horticultural oil is an oil-based pesticide used in horticulture and agriculture. It is an effective and ecologically friendly way to control and manage insects, mite pests, and even certain diseases. It is a valuable tool use to manage insects and mite pests on the edible garden, flowers, fruit trees, and even houseplants.

Horticulture oil became a popular way of controlling and manage insect and pest problems with all types of plants. Especially on fruits tree because it is an edible plant. Unlike chemical insecticides that remove all insects, oils allow pollinating insects to stay and do their helpful jobs.

What is Horticulture Oil?

Horticulture oil is a complex mixture of a vegetable (soybean and cottonseed), mineral, or petroleum-based oil. The oil is usually combined with an emulsifying agent such as water so that it can be used as a lightweight spray. Horticultural oil is considered safe and is the main form of organic pest control, as they are an effective and eco-friendly way to combat certain diseases, pests, and mites in the garden. Insects generally do not build resistance to horticulture oil.

How It Works

Spray the horticulture oil onto plant surfaces and directly onto the insects. When sprayed directly on the insect and pest in question, the horticulture oil spray will block the insects breathing spiracles and cause them to suffocate or smothered. Horticultural oil can also disrupt the development of insect eggs, starving them before they can cause further damage.

If you do not spray directly onto the insect or larva and cover it with the oil, it will not remove unwanted insects and pests.

How Safe Is Horticulture Oil

Horticulture oil is labeled as a pesticide, so always follow the label instructions and use it accordingly. Remember, only use horticulture oil when it is absolutely necessary because both bad and good bugs can be affected by the spray.

Horticulture oil needs to be spray directly on the insect or pest to be effective. The remaining oil will evaporate and dissipate quickly, so the spray is safe around pets and people.

When To Apply

If horticultural oil is needed during dormant months (Feb and March), apply it on the leaves or flower before the bud break in the Spring. This will help combat the pests before they arrive in the coming warm months. During Spring and Summer, you can use the oil again if necessary. By practicing both, it can help prevent and control insects at the different stages of their lives. 

Now, there is a difference between Summer and dormant oil. Summer or all-season oil is a lighter version of dormant oil. It is ultra fined oil, so it is less likely to cause phytotoxicity because it is cleaner and purer. On the other hand, Superior oil is less expensive and isn't as pure as summer horticulture oil, it can only be used during the dormant period.

If you are planning on purchase your horticultural oil from a store, be sure to read the instructions. 

When Not To Use

  • During High Temperature: Horticultural oils are not recommended when temperatures are around 100 degrees Fahrenheit because the plants are already experiencing stress in the extreme conditions. This makes them more susceptible to damage. 
  • During Freezing temperature: The same goes for freezing temperatures: the emulsion of oils won't hold together, and coverage would be uneven and spotty. 
  • Away From Sensitive Plants: Always check to make sure a plant isn't already known to be sensitive to horticultural oils. (Often, the oils have a list of plants to avoid on their labels.) Also, make sure no sensitive plants nearby or have tender new growth. 
  • Pesticide Contains Sulfur: Avoid using horticultural oils if you've used a sulfur-based pesticide recently, as this makes for a toxic combination for the plant in question. 
  • When Plants Are Too Wet Or During High Humidity: Spring is always an excellent time for plant maintenance, but avoid days with too much wetness and moisture because this increases the likelihood of evaporation and leaves the plant at risk of damage or burning. 
  • Avoid Spraying In The Fall: Many have noticed these plants tend to be at a higher risk of winter damage.

What Pests Are Controlled With Horticultural Oil?

Horticultural oil is effective on many types of insects, pests, and even diseases like powdery mildew. Horticulture oils are known to effectively control aphids, caterpillar eggs, leafhoppers, adelgids, mealybugs, scale, mites, spider mites, whiteflies, and thrips. Because of their effectiveness with aphids, horticultural oils help control the spread of viruses and disease from one plant to another.

Symptoms of Plant Damage

Phytotoxic symptoms may include foliage turns light yellow, leaves may appear water-soaked, turns to a dark color, and leaves drop from the plant.

Make It Yourself

Making horticultural oil yourself is a great way of controlling your indoor plants and garden plants' pests without bringing any harmful chemicals into your home. There are even household cleaners that contain traces of horticultural oils in their ingredients.

To make your own horticulture oil spray:

  1. Begin by mixing one tablespoon of liquid soap with one cup of oil. You can use cottonseed oil, soybean oil, or safflower oil.
  2. Find a spray bottle and mix 1 and ½ tablespoons of your mixture per every 1 cup of water. (Remember that too much oil will be too strong a solution and can cause damage the plant you are trying to save.)
  3. Shake the bottle well and spray on infected plants. The oil works best if you can spray it directly onto the pests. 

Remember: Oil and water don't mix. They separate constantly. Therefore, constant agitation of the liquid is necessary when spraying. Keep shaking that bottle between applications. 


Horticultural oil has become a popular option for pest control because it is eco-friendly and safer to use than traditional pesticides. It doesn't contain harsh chemicals known for adding their components into the plants, flowers, and fruits. Instead of making their way into the plant's makeup, horticultural oil is sprayed directly onto the pest or the insect and suffocate them to stop them from damaging your plants further. The safe use of horticulture makes them more appealing on another level.

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About the author

Bella has a Bachelors degree in interior design, is a master gardener. She designs nourishing outdoor & indoor spaces guided by the practice of Feng Shui.

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