Dormant Oil: What Is and How Do You Use It?

Dormant oil is a natural pesticide that protects plants but does not damage the fruit or environment.

Deciduous trees stripped bare in the winter season is a stark beautiful look, but sometimes a lonely sight.

label of Dormant Oil Pesticide

When trees including fruits trees lose their leaves in those colder months, it seems like they take a pause from life and do not need any care.

But, many trees need an extra level of protection against pesky insects. They want to make the trees their new home and food source in those dormant months.

What Is Dormant Oil?

There are many types of dormant oil sprays. In general, people use them on deciduous trees from fall to spring. You can find dormant oil for specific types of plants and a variety of uses.

Dormant oil is one of the preferred methods for tree care through the winter months.

These oil sprays mix readily with water. When prepared properly oil sprays control many pests that live through winter on tree trunks, twigs, and buds.

You can make your horticultural oil spray at home with ingredients from your kitchen. 

The term “dormant oil” implies that it is only for use during the winter months. But, many companies have produced lighter dormant oils usable all year on trees.

The sprays specifically made for the dormant months often have petroleum oil that smothers insects.

How To Use Dormant Oil

How you use dormant oil depends on the type of trees you have and what you would like to prevent. 

Types of Trees

You can use dormant oil on any deciduous trees once they lose their leaves. For non-fruit trees, apply the spray starting in late November and continue through until late February.

If you have fruit trees, the best time to spray dormant oil is during the late winter and early spring. There is no set date to apply the spray every year, so you have to depend on the weather. 

Once the temperatures stay over 40° degrees Fahrenheit for at least a full day, get outside and start spraying before new growth begins.

You can even apply the oil well into the month of April, as long as the trees do not have bud break.

Make sure to pick a time when there is no rainy or windy forecast. You don’t want anything to immediately strip the trees of the protective layer you just applied. 

Whether you’re spraying fruit or non-fruit trees, make sure not to get any oil on your annual flowers. You can cover them with a tarp to protect them during the process.

Use a pump sprayer to evenly apply the dormant oil all over the tree, starting at the top and working your way down to the trunk.

NOTE: Dormant oil sprays with a viscosity rating of 60-70 are known as “superior” oils. These oil sprays are safer than those with a viscosity of 90-120.

Superior oil, also called horticultural oil, is a highly refined miscible oil (up to 99.9 percent pure) that when mixed with water and sprayed on trees will smother overwintering insects and their eggs. [source]

Pesticide

If you want a dormant spray that fights against insects, like scales and aphids, choose a solution with refined oils.

The horticultural oil effectively smoothers and suffocates the insects, which lets your trees thrive throughout the winter months.

Dormant oil can help combat:

  • Mealybug pests
  • Peach twig borer
  • Spider mites
  • Insect and Caterpillar eggs

But, it is not an entirely practical choice against moths and orange worm pest problems.

Of course, not all insects are destructive! The great thing about using dormant oil is that all the beneficial critters you want in your garden are not usually active in the winter months.

As such, the spray won’t affect them. 

Disease Control

For trees prone to diseases, try a dormant oil with copper, like copper sulfate or cupric hydroxide. Other options for disease control include synthetic fungicides, such as chlorothalonil and iprodione.

Most commercial dormant oils have these synthetic formulas.

These solutions can fight:

  • Fire blight
  • Brown rot
  • Codling moth
  • Black spot
  • Different types of mildew 

How To Make Dormant Oil For Pest Control

While there are plenty of dormant oil products available at your local gardening store or online. You can make your own all-natural sprays right at home. 

If you want to protect your trees against mites, mealybugs, or aphids, the mix is quite simple.

All you need is:

  • 1 tablespoon of canola oil
  • 1 quart of water
  • Several drops of detergent

NOTE: Cottonseed oil and Soybean oil are more refined and can be used instead of canola oil.

Just like the refined oils in commercial products, the mixture suffocates any unwanted pests. 

Using regular dormant spray with petroleum oil may not be the most all-natural option for fruit-bearing trees. Instead, you can make your own concoction with two tablespoons of liquid and a cup of vegetable oil. 

Both mixtures work just as well as petroleum dormant oils and provide a much safer option for your fruit trees. 

A good general rule is to use application rates of 1%. Always read the label before applying any sprays to your plants.

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