All About Dormant Spray

It’s the winter season, which means it’s time to get out the dormant spray!

Thanksgiving, Christmas and Valentine’s Day are good markers to remind us to do something nice for our fruit & flowering trees, grape vines, berries, roses, and lilacs.

The Pacific Northwest with its mild, damp conditions is a wonderful place to garden. It is also the fungus capitol of the universe. These fungal spores over-winter in the crooks and fissures of bark and twigs, and may manifest during the growing season as troublesome diseases.

Dormant sprays are compounds that assist us in controlling fungal diseases and many insect infestations, and are used during the winter season while the plant is in its dormant phase. (The plant is dormant, not the spray!)
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Common dormant spray materials are acceptable by organic certification standards. Although approved by the EPA for organic use, exposure to the eyes and skin is dangerous and should be applied with caution. Wear long sleeves, gloves and goggles when spraying, and avoid the windy days. As boring and tedious as it may be, always read the label and follow the directions. A special note…more is not better. Under certain conditions, plants may be damaged by using a concentration that is too strong.

Copper Sulphate – Copper Sulphate is a dormant spray and a very good fungicide. While you can use it on any tree, it is the only kind of dormant spray that should be used on Peach and Nectarine trees.

Dormant spraying is the most cost effective method of disease and insect control. It is essentially a sanitizing process performed when the plants are resting. Prevention is the key to success. The spray is applied to the bare limbs and twigs of the plant, thoroughly wetting down the bark, covering all sides until it drips.

The first spray, when done in late autumn or early winter is like putting a raincoat on the plant. Fungal spores blow around in the wind all winter in the maritime northwest. This spray applies a protective coating, which prevents these spores from getting a toe-hold in the bark of the tree or shrub. The second spray, done around Christmas time is an added bonus, but if you are going to skip a spray, this is the one to skip. In the event only one spray can be applied, this should be the Valentine’s Day or late winter/early spring spray. This is the spray that will control apple scab, which can be a serious pest on apples, crabapples and pears. This is known as a delayed dormant spray. Delayed dormant sprays are applied from the "green tip" stage to the "half-inch green" bud growth phase. When the leaf buds are just beginning to emerge and the plant is just starting to come out of dormancy is the time to do this spray. This is by far the most effective time to wipe out the apple scab spores and many newly emerging insects that have just pounced on the fresh green buds. Timing is critical as sprays applied after this can injure the young leaves.

It’s important for the spray to dry on the plant. If it rains within 24 hours of spraying…yup, that’s right, you need to get out there and do it again. So watch the weather report and wait for just the right timing. Look for an above freezing, dry, calm day and apply!

No method of insect and disease control can substitute for good cultural practices in gardening. Healthy plants have their own mechanisms for fending off pests. Don’t forget about healthy soil, appropriate fertilization, adequate water, proper location, correct pruning, debris clean-up, and an appreciation for the alluring wonder and beauty of growing things. And enjoy your Holidays!