Dormant Oil: How to Protect Your Plants from Insects

TLC Landscaping Design & Pools

After a long and cold winter, many of us may be in a hibernative state of our own. Despite our reluctance to assess outside chores, the upcoming months require an important task to help protect trees and plants, especially if you noticed insect problems on small trees or shrubs last year.

As certain trees and plants remain asleep, early in the spring is the perfect time to apply dormant oil to protect from insects. Due to the harmful side effects of certain pesticides, many people have switched to using natural mineral oils, such as dormant oil, to treat plants.  

What is Dormant Oil?

Dormant oil is a heavyweight horticultural oil. Horticultural oils are recommended as a fairly safe insecticide, because they smother insects rather than poisoning them. Many of the new brands of dormant oil have an emulsifier added to help keep the mineral oil dissolved in water.

How is Dormant Oil Used?

To effectively apply dormant oil, it is best to start at the topmost branches and work the way down. You also want to focus on spraying all around the tree, shrub, or bush to make sure you get into all the crevices.

The oil helps control and kill insects such as blister and rust mites, red mite eggs, scale insects, plum black knot, and overwintering fungal diseases.

Dormant oil is not harmful to plants but it can damage leaves if it is applied after the bud has begun to unfold, which is why it is important to know when to use dormant oil.

When Should I Spray Dormant Oil?

There are a few common ways to tell if you may need to use dormant oil. Use dormant oil if your plant died out earlier last year, you can see the scale on the branches (white flecks on spruce and pine), or you saw insects eating leaves.

In terms of application it is best to spray dormant oil when the temperature stays above freezing for 24 hours. The best times are often from February through March, as the temperature usually remains at 0°C (32°F).

As with any insecticide, you want to make sure you know what the problem is and if dormant oil is the right solution. If you are unsure about dormant oil being the right treatment, or you want to book to have your plants treated, contact the TLC condo care team today.

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