How Many Times Should I Spray Apple Trees?

Use carefully timed chemical treatments to protect your apple tree yield from problems that could threaten it.

Growing apple trees at home can offer unparalleled rewards, most notably being able to pull home-grown apple right off the tree branch and eat it. But to invest the significant time and effort needed to grow apples at home only to lose your apple yield to insects, disease or other problems would be a substantial waste. Chemical treatments -- insecticides, fungicides, herbicides, miticides and the like -- can be an effective weapon in protecting your apple trees from these threats, though they always need to be carefully timed to be most effective.

Species Identification

The first step in knowing how often to spray an apple tree with an insecticide, fungicide or other chemical is to accurately identify the species that is attacking it. For example, to use an insecticide approved for use against the codling moth when the pear psylla is actually attacking your apple trees will be marginally effective at best. Seeing the insect infestation persist on your apple tree may tempt you to apply more insecticide and more often, while a single application of an insecticide targeted at pear psylla could have effectively removed the infestation. Carefully identify the insect, fungus, disease, mite or other threat that is attacking your apple tree.

Method of Delivery

Chemical treatments for plants differ fin their method of delivery, and these differences have a dramatic impact on how often you should apply these chemicals. Preventative chemical treatment such as horticultural oils and systemic fungicides are applied before the growing season to prevent the problem before it occurs and are typically only applied once per growing season. "Rescue treatment" chemicals, on the other hand, such as contact insecticides, are used after a problem is discovered and may need to be repeated if the problem is not resolved by a single application. Be sure to understand which of these two types of chemical treatments are the chemicals you purchase before using them.

Manufacturer's Instructions

The most important way to know how often to apply chemical treatments to your apple trees is to follow the manufacturer's application instructions exactly. Every manufacturer of chemical treatments for apple trees designs an application schedule around the specific properties of the active chemical ingredient they use and on the health needs of the apple tree. Never deviate from the manufacturer's printed application directions.

Other Considerations

It is impossible to overstate the importance of choosing the right chemical treatment when considering how often to apply that chemical treatment. A single application, much less repeated applications, of a chemical treatment that is not approved for safe use on apple trees can inflict serious harm on your apple trees, often much more serious harm than can be inflicted by the problem being treated with the chemical. Choosing a chemical spray treatment that is both safe for apple trees and targeted at the specific problem will go a long way in protecting the health of your apple tree.

References

• University of Rhode Island Landscape Horticulture Program; Home Tree & Small Fruit Pest Management Guide
• Colorado State University Extension; Apple and Pear Insects; W.S. Cranshaw & R.J. Zimmerman
• University of Idaho Extension; Fruit Tree Insect Pests
• Ohio State University Extension Fact Sheet;Growing Apples in the Home Orchard; Gary Gao