Dormant spraying combines Horticulture Oil and Lime Sulphur to kill overwintering insects (such as scale and mites), insect eggs, and diseases on certain hardy landscape plants.
What Plants Benefit From a Dormant Spray Application?
Dormant Oil and Lime Sulphur are best applied to fruit trees, roses, ornamental shrubs like Highbush Cranberry and European Snowball, evergreens such as Cedars, Green Junipers, and Euonymus, and trees like Hawthorn, Crab Apple, and Honey Locust.
Do not use a dormant spray on Beech, Butternut, Colorado Blue Spruce, Hickory, Holly , Sugar Maple, Japanese Maple, or Walnut.
When to Spray
This combination spray can only be applied when plants are completely dormant.
Applying at the incorrect time can burn leaf buds that have started to swell or show any sign of green.
Choose a day from February through March when the temperature will remain at 0°C (32°F) or above for a minimum of 24 hours.
Distribution of the spray will be more efficient on a day without wind. Higher wind speeds will result in little of the mixture adhering to the plant.
Dormant Spray will coat and dry most effectively when no rain, snow, or sleet is in the forecast.
Spray early in the morning so the plant will be completely dry by evening. Do not spray if there is any chance of frost overnight.
How to Spray
Mix Lime Sulphur and Horticulture Oil (available together as a Dormant Spray Kit) according to the package directions. The easiest method of application is to use a specific Dormant Spray Applicator that attaches to your garden hose.
You can also mix the spray according to the box instructions in a 1 or 2 gallon tank sprayer.
For small jobs, use a handheld mister bottle or pump sprayer.
In all cases, spray the plant starting at the top until it just starts to drip off the branches. If you start spraying from the bottom, you will run out of product before the job’s done.
For roses, be sure to spray the soil around the base of the plant as well to control Powdery Mildew and Black Spot.
Mix only what you can use. You cannot save the prepared solution for later use.
For spraying any garden pesticide, wear protective clothing, long sleeves, a hat, chemical-resistant gloves (not your kitchen rubber gloves), and anti-splash goggles.
Wash hands and face after use.
Do not let any of the mixture fall or drift onto such hard surfaces as interlock, natural stone, brick, concrete, stucco, wood, or aluminum siding as it may leave a permanent stain. If necessary, tape a large piece of plastic to the area first, and then spray.