Spraying fruit trees in winter with dormant oil spray is an essential part of fruit tree care, for insect and fungus management. The mixture of white oil and copper fungicide is applied during the dormant season (winter), preferably late winter, up until a couple of days before buds open, to prevent pests and disease in your fruit tree. In this article, I will show you how to apply dormant oil and copper spray like a winter wash for fruit trees to prevent pests and disease in your fruit trees.
What Is Dormant Oil
Dormant oil ingredients
Dormant oil sprays are horticultural oils, a mixture of several ingredients including petroleum or vegetable oil (also known as white oil), emulsifier to enable water to mix with, and copper fungicide. It is applied as a dilute spray in late winter or early spring to spray fruit trees for the prevention of pests and disease. The oil is called dormant as a reference to the season of usage i.e. when fruit trees are in the dormant period.
Can you mix dormant oil and copper?
Yes, you can mix dormant oil and copper fungicide. However, I prefer to buy the oil that already has both white oil and copper fungicide included in the package.
How to Use Dormant Oil on Fruit Trees
Step by step process
- make sure all plants in the vicinity of your trees are well covered with a plastic sheet to prevent oil drops from reaching them
- get a large bottle of water, tank sprayer (pump sprayer), measuring cup, and a package of dormant oil
- carefully read the label on the packaging, and follow safety instructions
- mix the right amount of dormant oil (usually 1-3% ) with water and fill the sprayer
- slowly and cautiously spray the trees: cover the whole tree with the mixture, every single branch from top to the bottom of the tree, the entire surface of branches and trunk to the very bottom, and a bit around the ground (I usually spray a circle of about 10 cm of soil around the trunk)
- after the application, rinse well all your oil kit to keep it clean for future use.
Dormant oil spray kit
My dormant oil spray kit consists of a 2 liters manual garden sprayer with a pressure pump and adjustable nozzle, a large bottle of water, an empty yogurt cup as a measuring cup, and a bottle of commercially available dormant oil and copper fungicide.
When to Apply
When should dormant oil be applied?
You can apply dormant oils any time during the dormant season, but the best results are achieved in late winter or very early spring at least a few days before you expect the buds to open.
The temperature should be well above freezing (at least 5°C) and the weather forecast should predict at least two days (48 hrs) without rain or high winds.
How long does it take for dormant oil to dry?
Ideally, spray in mid-morning on a calm and sunny day, with no wind to leave enough time for the oil to dry before the evening dew. It takes about a couple of hours for dormant oil to dry.
You can repeat application in 2-3 weeks.
When is it too late to spray dormant oil
If buds on your fruit trees are swollen and already started to open, it is risky to apply the oil. In case you just miss the right time, let’s say for few days or a week, you can still apply the oil but in a lower ratio than recommended on the label.
What I usually do in this case is mix just 0.5 or 1% of the oil with water instead of recommended 3%. As you can see in the above photo, the almond tree buds are still containing traces of recent oil application although they are already started to emerge. Be very careful with applying the oil too late to avoid dormant oil bunnings on your tree.
How often can I spray dormant oil and copper fungicide?
You can spray dormant oil with copper once a fortnight up to three times per dormant season. Just make sure that temperatures are well above freezing.
Here are two videos of the process – In first video you can see me preparing the oil mix and spraying my young fig trees
In next video I am winter spraying my young almond trees:
I usually winter spray my fruit trees immediately after winter pruning to prevent the spread of disease on pruning cuts that are not healed yet. Alternatively, use grafting wax for larger cuts.
In next article I will show you how to make homemade dormant oil.