DORMANT SPRAYING TO REDUCE INSECT & DISEASE
SPRAYING: (January, February and March)
Use Horticultural Oil and Lime Sulphur in combination mixed with water. Apply to dormant trees before buds break, which is a very important application as it destroys many insect eggs on the bark, kills overwintering adult insects and helps to prevent fungal diseases.
Most directions for use do not recommend dormant sprays for evergreens, only deciduous trees and shrubs.
Spray in the morning to allow quick drying of the spray. Injury may occur to tree if spray is not completely dry before a cold night. Do not spray in temperatures below 4°C or above 27° C. Only 1 application is necessary with this combination spray before buds start to swell as long as good coverage has been achieved.
Lime Sulphur may be used alone during the growing season; read instructions carefully before use. Do not spray in windy conditions or when it’s raining and the trees are wet. Neither should you spray when the temperatures are freezing, as horticultural oil will break down in cold weather and not be effective. You need 24 hours of above freezing, or you will have to spray again. Clean out sprayers after use with soap and water to avoid corrosion.
Do not use Horticultural Oil on Sugar Maple, Japanese Maple, Beech, Butternut, Colorado Blue Spruce, Douglas Fir, Hickory, Holly and Walnut. Horticultural Oil will damage the bark on Empire, Mutsu and Red Delicious apple trees. Do not use Lime Sulphur on Apricot. Do not use Lime Sulphur on Plum trees when they are in leaf.
Application rates can vary. Follow manufacturers recommended rates and read labels carefully.
Best coverage is achieved with a pressure sprayer, not a hose end sprayer and most directions specify them to achieve control.
INSECTS AND DISEASES:
The following may be controlled by the application of HORTICULTURAL OIL / LIME SULPHUR COMBINATION:
- SCALE – Attacks apple, peach, pear, plum & cherry. Tiny insects under hard scales that cause damage by sucking sap from the leaves and tender branches of the tree.
- MITES -Attack apple, peach, pear, plum, & cherry. They are tiny spider-like insects which siphon sap from leaves, spinning microscopic webs.
- PEAR LEAF BLISTER MITE – Causes dark red to brown spots and leaves, eventually weakening the trees overall health.
- PEAR PSYLLA – Sap sucker, which causes excrement (honeydew) to turn black and sooty. Leaves turn pale with dead areas, eventually damaging fruit and weakening tree.
- APPLE SCAB – A disease that causes dark spots on leaves and fruit. Leaves may drop and the crop may be reduced the following year.
- BLACK KNOT – An extremely infectious disease of plum trees causing hard, crusty, black swellings several inches long on branches and small twigs.
- PEACH LEAF CURL – Causes foliage to curl and form reddish blisters on leaves. They eventually turn yellow and drop, weakening the tree.
- POWDERY MILDEW – The white, powdery mildew turns to a brown felt-like coating on foliage, twigs and fruit.
- RUST / FUNGUS – Orange spots, later growing into pimple like lesions, that appear on lower leaf surfaces.
- ANTHRACNOSE -Affects canes on Raspberries, causing discolouration and cracking of bark, resulting in spoilage of fruit.
- SPUR BLIGHT – Attacks canes of Raspberries. Canes may be weakened and killed overwinter.
NOTE: Timing of spray is critical to success. Watch the swell of your buds on trees and shrubs you are going to spray, and apply just before they break. For example, a good time to spray roses is when the forsythia is blooming. If timed too early, the lime sulphur will not be effective.
For more information on specific insects or diseases like peach leaf curl, see our Fruit Tree Fact Sheet Book at the information desk.