Reduce Pests & Diseases on Trees and Shrubs With Dormant Oil

Did you know, there is a pretty slick way to get rid of pests and diseases on fruit trees? I highly recommend adding this solution to your regimen.

In addition to being fairly inexpensive, dormant oil is considered less harmful and toxic than many other pest control methods. While dormant oil will not completely eliminate problems, it can reduce pests and diseases by 80-90%! 

Let’s talk about what dormant oil spray is and how you use it to avoid a pest infestation or disease later in the season.

Controlling Pests Organically in the Orchard

I’ve shared blog posts on planting fruit trees, a guide to fruit tree spacing, how to prune fruit trees, and how to use tree guards to protect young trees from girdling. Now, it's time to discuss preventive pest control methods for your trees.

What Is Dormant Spray

A dormant spray is an application of one or more different horticultural oils applied during the offseason that help to control pests and diseases. It is a gardener's first step in preventing issues that can occur during the main growing season! 

Pest control in fruit trees can be tricky because, while there are a whole host of pests specific to peach trees, there is a different group of pests specific to apple trees, and so on. However, dormant sprays can help control essentially all pests on all types of fruit trees, ornamental trees, and shrubs by smothering them with oil.

Even though you may not notice problems until the main growing season, a lot of fungi get started in the damp conditions of late fall to early winter or late winter to early spring. A good dormant spray will combine a horticultural-grade oil, typically neem oil, with a fungicide to control fungal diseases such as peach canker, leaf curl, and fire blight. 

Plants That Benefit From Dormant Oil

Many trees and even shrubs will benefit from dormant oil spray because it knocks down dangerous numbers of harmful insects and combats fungal diseases. You can absolutely apply this dormant oil spray to any dormant fruit tree! 

Peaches are my main focus, but I will also be using it on apples, pears, plums, pecans, nectarines, and apricots. I have attached links to the product labels I used below, which provide a complete list of plants you can use them on.

Diseases & Pests Controlled

The list of pests and diseases controlled by this dormant oil spray is too long to list here! Check out these product labels for a complete list of diseases and pests controlled: 

• Copper Fungicide product label for a list of plant diseases controlled

• Fruit Tree Spray product label for a list of insects and diseases controlled

When to Use A Dormant Oil

The time to use a dormant oil is when the trees are dormant and there are no pollinators out. Dormant oils are designed to minimize the negative impact on beneficial insects, as they are applied when pollinators aren’t active. 

Studies indicate that 3 to 5% (some say 7%) of beneficial insects can be harmed by dormant oil, while approximately 80 to 90% of harmful insects (the ones that cause significant damage to your plants and set back your yields) will be controlled. For me, the pros outweigh the cons.

I always want to be mindful of beneficial insects whenever I use any spray or pest control method, including organic pesticides! That is why the dormant season is an ideal time to spray.

The first application of dormant oil usually happens around Thanksgiving, after leaf drop in late fall to early winter. You want the temperature to be above 40°F with no active rainfall anytime you spray dormant oil, and for it to stay that way for a few hours after spraying so that the oil can dry and set on the tree.

The second follow-up spray of dormant oil should happen around mid-February up until early March, depending on your weather. Spray before the buds begin to swell in the spring. 

Pro-Tip: Don’t spray dormant oil once the buds begin to swell! Pollinators become active at bud swell, and you do not want to harm or kill the beneficial insects that are helping your plants!

Supplies Needed

I recommend gathering these supplies before the day you plan to spray, if possible. Then, when the timing and weather are right, you can spray without delay. You will need:

• Copper Fungicide - This is a better option for gardeners who want to keep harmful chemicals out of their garden! You can use copper fungicide throughout the seasons for blight, powdery mildew, rust, grey mold, and other fungi that attack trees, shrubs, and garden plants.

• Captain Jack’s Fruit Tree Spray - This spray contains about 70% neem oil to smother insect eggs, scale, and other pests. This is really going to knock down the insect numbers on your trees and shrubs! I love to use Captain Jack’s Fruit Tree Spray specifically because it contains not only neem oil, but also a few other ingredients like wettable sulfur, which acts as a fungicide as well. 

• Pump Sprayer - You will need a 1 or 2-gallon pump sprayer to apply the dormant oil. I used a 2-gallon sprayer in the video because I have a lot of trees to spray.

How to Use Dormant Oil Spray

Wait for the ideal conditions before spraying dormant oil: the plants should be dormant, it shouldn’t be windy, and the temperature should be above 40°F with no active rainfall at the time of spraying and for a few hours after.

If you are combining ingredients (like I do in this tutorial and video), make sure to follow the instructions to the letter! If you overapply, you absolutely can kill your trees. If you are using a different product, make sure you read the product label for the specific dormant oil you are using.

1. Determine the Amount of Spray Needed - Follow the application directions on the label to calculate the amount of spray required for the number and size of the plants you need to spray. (The directions that follow are to mix one gallon of dormant oil spray.)

2. Add Water - Pour 1 gallon of water into your pump sprayer.

3. Shake - Shake the original bottles of oil and fungicide well before mixing.

4. Add Fungicide - Measure out the directed amount of Copper Fungicide and pour it into your pump sprayer. (I used 1 Tablespoon, which is 0.5 ounces, per gallon of water.)

5. Add Insecticide - Measure out the directed amount of Captain Jack’s Fruit Tree Spray and pour it into your pump sprayer. (I used 2 Tablespoons, which is 1 ounce, per gallon of water.)

6. Agitate Thoroughly - Put the lid on the pump sprayer and shake it very well. You need to agitate it thoroughly to emulsify the oil and water together so that the oil will actually stick to the trees.

7. Spray Trees and Shrubs - Starting at the top branches and working down, thoroughly soak each tree with the spray until it is dripping. Spray all over the tree including the trunk, making sure to get into any crevices. Remember, the goal is to smother insects and their eggs so going light on the spray won’t help you achieve that. Pro-Tip: It is essential to spray upwind so that the spray is doesn't blow back at you! 

It usually takes 15 to 20 minutes for the spray to dry. Once it is dry, it will work for about 3 or 4 weeks and should have done its job in that time. As stated earlier, I recommend spraying trees twice in the dormant period, once in late fall and again in late winter before bud swell.