Back to Info Sheets	Dormant Spraying: Attack Insects Before the Damage Occurs Once we can depend on the milder weather with temperatures staying above freezing,  it is time to start some very important projects in the garden.  This is particularly true for those who have established fruit trees such as apples, peaches, and pears in the garden, or possibly a bed of roses.    Late April is the time to apply dormant spray to fruit trees, to roses, and to certain ornamental shrubs that are susceptible to scale insects and spider mites.  There are two types of dormant sprays -- a dormant oil spray or lime sulphur.  These sprays are applied before the leaf buds begin to break, but only while the temperature will be staying above freezing for two to three days to allow for through drying.  The dormant oil spray kills overwintering aphids, spider mites, scale, pear psylla, and some other insects on fruit trees, roses, and some ornamental shrubs.  Scale insects are those immobile, bump-like insects often found on the trunks of fruit trees and some shrubs such as lilacs and euonymus. Lime sulphur is particularly effective in controlling some disease such as black spot on roses, powdery mildew, apple scab, and peach leaf curl.  When applying lime sulphur to roses as a dormant spray, be sure to spray all of the stems and the ground around the plants, This spray will help to destroy the overwintering stages of such disease organisms. Lime sulphur can also be used to control some insects such as the maple gall mite and the spruce gall aphid.  The lime sulphur and dormant oil can also be mixed together to control certain insects and diseases.  These are both strong sprays and must be applied while the plants are dormant and before the buds begin to break, as they will burn tender young growth.  To control black knot of plums and cherries, a lime sulphur spray should be applied just as the buds break.  As with all pesticides, read the label very carefully and follow the instructions exactly.  These sprays cannot be applied to certain trees and shrubs as noted on the labels.   Vol. 97 no. 25
© Murray's Garden and Horticultural Services Last updated: March 2, 2008