By matching three things: the pest, the tree, and how the product reaches the pest. An insecticide is the right choice only when both the tree and the pest appear on its label and when its method, whether a spray, a soil drench, or a trunk injection, can reach where that pest feeds.

Why does the label decide the choice?

A label lists the plants and pests a product is approved for, along with the directions and precautions for using it. An insecticide applied to a tree or pest its label doesn't cover is a guess, so the label is the first filter before any other comparison.

How does the pest narrow the options?

By where and how it feeds. Caterpillars and other chewing insects are reached with leaf sprays such as spinosad or Bt, soft bodied sucking insects like aphids and mites with insecticidal soap or horticultural oil, and boring insects with a systemic soil drench or trunk injection that travels through the tree.

How does the tree narrow the options?

By its size and whether it bears fruit. A tree too large to spray points to a systemic treatment, while a fruit tree needs a product labeled for food crops, which rules out trunk injections not meant for food bearing plants. One part Safer Brand Insect Killing Soap mixed with 50 parts water makes up to 6 gallons of spray that is labeled for trees, fruits, and vegetables and can be used up to the day of harvest.

Frequently Asked Questions

Should a fungus be ruled out before choosing an insecticide?

Yes. Spots, cankers, and powdery coatings usually point to a fungal problem that calls for a fungicide, as the guide to telling a fungus from a pest problem explains.

Can an insecticide be applied while the tree is flowering?

Usually not. Applying during bloom is avoided to protect bees and other pollinators visiting the flowers.

How soon should treatment start?

At the first signs of the pest. Boring insects in particular become extremely difficult to control once they are established inside the tree.

Are there organic options for trees?

Yes. Spinosad sprays, insecticidal soap, and horticultural oil include options approved for organic gardening.