Horticultural Oil: What Is It And How To Use It In The Garden

horticultural oil

The use of horticultural oil, is a common way to eliminate pest issues for fruit trees and gardens. Many people struggle to control the garden pests and keep them at bay. After exhausting other means of pest control, many turn to horticultural oils also called a spray oil.

You must remember not all insects are pests. Lady Bugs, for example, control aphids. Unfortunately, oils will harm both the good beneficial insects and the bad insects, so take care and evaluate the situation prior to using horticultural sprays.

What Is Horticultural Oil?

When it comes to pest control you’ll find oils to use which can eliminate garden pests. Derived from petroleum, oils they work by coating the outside of a bug (scale insects), and prevent them from proper breathing and eating, suffocating them.

Spray oils extracted from plants can also naturally eliminate pests. Mix the oil with water and a little Dawn dish soap into a sprayer or a spray bottle and apply on plants struggling with insect issues.

You’ll hear several names get thrown around to describe the oil:

  • Dormant oil
  • Volck oil
  • Dormant spray
  • All seasons spray oil
  • Summer oil

How And When To Use Horticultural Spray In The Garden?

Reach for horticultural oils after exhausting all other pest control options. Oils work very well on most plants, however, always check the labeling before applying them. Some oils perform better when applied during a plant’s dormant period and only under specific conditions (temperature as well as humidity).

Applying a “dormant oil” helps kill off any wintering insects like mites, scale, and aphids without harming the plant.

Horticultural spray oils when first introduced were heavy oils. Today, these refined “light weight” oils like Bonide All Seasons Spray Oil (amazon) now allow the safe use on many plants throughout the entire growth season as needed. Apply the oil, it dries up and becomes non-toxic to plants, but effective in pest control. Also, use oils to help control powdery mildew or mold.

The term “dormant spray”, refers to the proper timing to use the oil and not the kind of oil utilized. Always refer to the label for application directions.


Use Spray Oils On What Type Of Plants?

Using horticultural oils to kill scale and soft insects on woody ornamental plants make for a lethal combo. Unfortunately, they also kill off any beneficial insects as well. Take great care to ensure the proper application and use of sprays on plants that can tolerate the oils.

The oils don’t harm the plant, just the bugs. They work by suffocating the insects as well as their eggs. They also affect how the insects eat and can poison the insects as well as suffocate them. Additionally, one insect may carry the oils to other insects and contaminate the entire nest.

In order for oils to work effectively, insects need to be totally covered. Once the oil dry’s on the plant the oils no longer work on the insect pests.

Plants NOT To Use Oils On?

Never use oils with any aquaponic gardening, the oils are toxic to fish. Don’t use oils on plants such as:

  • Maples
  • Junipers
  • Spruce
  • Cedar or other such Evergreen plants
  • Japanese as well as Red Maples
  • Hickory and Black Walnut plants.
  • Plume cedar
  • Smoke Tree – very sensitive

If plants show a yellowing of leaves or needles after application, do not used again on the plant. This usually indicates a burn and could cause further damage if used again.

Make every effort to eliminate pests with other methods prior to seeking out horticultural oil. Never apply oils in freezing temperatures, droughts or extreme heat and ALWAYS read the chemical label.

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