What Do I Need to Spray on My Fruit Trees?

Fruit tree sprays keep pests out of trees.

The happy little worm drawn in an apple in a children's coloring book is actually the reason that apple trees need to be sprayed. Pests like the coddling moth that live out their larvae state inside apples will infest fruit if they are not killed or repelled through a process of spraying. Most fruit trees are put on a regular schedule of spraying throughout the year to guard against pests, diseases and fungus.

Dormant Oil

Dormant oils are typically applied to trees while they are still dormant. The oils are used as a preventive measure to kill eggs that some insects lay on trees, insects in a dormant nymph state and scale bugs. The oils coat the surface of the insects and egg sacs to smother the pests. Dormant oils are highly refined so that they will not harm the tree. The oils should never be applied to trees once they begin to set buds. Dormant oils sprayed on budding trees may cause the tree to drop its buds.

Fungicide

Fungicides help to kill fungus and stop the spread of spores that travel from tree to tree. This can stop the spread of major diseases such as fire blight. Copper of some type is a major component of many fungicides. A copper-based fungicide known as a Bordeaux mixture is approved for use by organic growers. Bordeaux mixtures combine copper sulfate, lime in the form of crushed limestone and water. This mixture will also help to fight off bacteria that can harm fruit trees. Fungicides are typically applied only if fungus diseases are active in an area, if a fungus was active during a previous year or if a tree starts to show signs of fungal infections.

General Purpose Pesticides

Because orchard growers have no way of knowing what pest will attack a tree or when it will attack, most growers use a general purpose pesticide that they can spray on a weekly basis. General purpose pesticides simplify spraying fruit, although reliance on a general purpose pesticide can be wasteful at times. Some gardeners rotate between using pesticides to avoid having pests build up a tolerance to any single pesticide. Garden supply stores sell pesticides under various names. The active ingredient of the pesticide is frequently sold in higher quantities in concentrated form.

Supplemental Sprays

If an area is threatened by a specific pest or disease, gardeners may wish to add a supplemental spray to their routine. Supplemental sprays may be used on an as-needed basis. For example, some gardeners spray with a bacterium, Bacillus thuringiensis, that attacks pests such as caterpillars. Using supplemental sprays can help increase fruit yield by attacking pests or diseases that a general purpose spray will not affect.

References

• Iowa State Univeristy Extension; 2011 Midwest Tree Fruit Spray Guide; Rick Weinzierl, et al.; January 2011
• University of New Hampshire Cooperative Extension; Home Fruit Spray Schedule; Alan T. Eaton, et al.; June 2010
• University of California Extension; Bordeaux Mixture; J.C. Broome, et al.; June 2010

Resources

• University of Kentucky Extension; Garden Fungicides; John Hartman, et al.; May 2005
• Texas A&M University Extension: Dormant Oil
• University of Missouri Extension; Fruit Spray Schedules; June 2010