Guide to spraying fruit trees
Fruit trees must be protected against harmful insects and disease to produce attractive, nutritious fruit. Proponents of Integrated Pest Management (IPM) practice low- or no-spray methods but are not opposed to the use of chemical controls when necessary.
Low-toxicity fruit-tree pest-control sprays use materials such as neem oil, rosemary oil, peroxide and select bacteria as the base ingredient for fungicides and pesticides. Whether the home gardener uses traditional sprays or low-toxicity sprays, there is a yearly schedule of fruit tree care to follow.
Winter Dormant Season
Dormant oil is the term for any oil sprayed on fruit trees during the dormant season to control scale, aphid eggs, mite eggs, pear psylla and peach twig borer. Oil blocks the air holes (spiracles) through which insects breathe. It is non-toxic to humans and beneficial insects. IPM gardening methods encourage the support and protection of beneficial insect populations that are natural predators to harmful insect pests. Dormant oil works on contact with insects and must be sprayed thoroughly over all tree areas. Spraying is done in dry weather when temperatures are above freezing.
Spring Bloom Season
Pear, peach, nectarine, apricot, apple and plum trees are sprayed with a fungicide in early spring when buds begin to show colour and green tissue is 1/2 inch out of the bud. Scab, powdery mildew, brown rot and fungus are controlled with chemical- or biologically-based fungicides. Malathion, captan, and carbaryl are ingredients traditionally used in chemical sprays. New-generation fungicides approved for organic production consist of microbial antagonists that suppress pathogens that attack fruit trees. Spring spraying is done at 10- to 14-day intervals until two weeks before harvest.
Summer Growing Season
Insects such as the peach tree borer that have not been successfully controlled during the spring spraying season are difficult to eliminate in summer's harvest time. Large amounts of gummy substance exude from the tree trunk when borers are present. It can be killed with a knife or flexible wire probed into its hole. A biological control that uses the Bacillus thuringiensis (B.t.) bacterium is one of the new non-toxic sprays used weekly during the peak period of moth flight in July through August. It controls larvae before it enters the trunk.
Fall Harvest Season
Spraying a fixed-copper fungicide in fall (typically November) controls shot hole fungal disease on peach and nectarine trees. It prevents fungal disease from entering into the tree limb by creating a surface barrier. It requires thorough spraying to create the disease barrier. Fall harvest season is an important time to clean up all debris around fruit trees so pests do not overwinter and cause disease in spring. Coddling moths live in fallen fruit, and diseased branches harbour harmful insects.