Dealing With Fruit Tree Pests and Diseases

• Introduction
• What Variety of Trees Should I Plant?
• Squeezing All This Into Your Back Yard
• Preparing the Soil and Planting
• Establishing the Trees and the Initial Pruning
• Summer Pruning
• Pests and Diseases (this page)

You and your family are going to be eating this fruit (and anything you spray on it), so choose your weapons accordingly. Stick with safe organic treatments, we have listed some here.

Pests

First we'll deal with the big ones because they are capable of doing so much damage so quickly. Deer can be fenced out. To keep cats from scratching the bark on young trees, surround the trunk with temporary fencing. Birds are not usually a problem, but netting is available if you need it. Neighbors can be discouraged in various ways from helping themselves, but you're on your own there.

The more insidious pests are the smaller ones. Treatment depends on which pest you will need to control. The best single preventive we have found for this part of northern coastal California is Spinosad, a soil bacteria (Saccharopolyspora spinosa) which affects the insect's nervous system. It is sprayed on the trees and can be used to control fruit flies, caterpillars, leafminers, thrips, sawflies, spider mites, ants, and leaf beetle larvae. It will not harm sucking insects such as most predatory mites, ladybugs, or lacewings. It will not harm bees after it dries. Follow the directions on the label.

Change the oil. Uh, what? In winter, before the new flower buds and leaves open, spray a lightweight dormant oil on the bark. You can buy it at the garden centers and most hardware stores. Coat the tree from all sides and directions. This will smother any eggs (they have to breathe, too) that the bad bugs have laid in the crevices. Don't make it easy for them, next year's bugs will have to come from somewhere else.   

Diseases

The most prevalent plant disease problems in this part of Northern California are scab, leaf blight, mold, mildew, rust and bacterial spot. The best single preventive treatment we have used is Serenade, another strain of bacteria (Bacillus subtilis) which forms a protective coating around all parts of the tree, discouraging the establishment of fungi. This can be purchased as a concentrate or in a ready-to-use form. Start applying this at the first sign of foliage and continue as needed. Follow the instructions on the label.

Good housekeeping will go a very long way in keeping fruit trees healthy. Leaf diseases come back next year because the spores overwinter in the ground. If diseased leaves fall off the tree and remain on the ground, the spores will overwinter there and will infect next year's leaves. Remove diseased leaves and you break the cycle.

NEXT: Back to the Introduction.