JoAnne Skelly: Getting ahead of fruit tree pests

Pest management is an important aspect of growing fruit successfully. Combining an assortment of tactics that cause as little disruption to the environment as possible while managing pests effectively is the best management strategy.

Timing of pest control is important. Use horticultural oils to control aphids, scale and other slow-moving pests while trees are at the dormant, delayed dormant or 1/4-inch green tip stage. Delayed dormant stage is when buds on most fruit trees are swollen. The 1/4-inch green-tip stage occurs when the spring leaves start to emerge. Oils smother and suffocate overwintering insects and eggs before they hatch.

Horticulture oils are safe for humans and the environment when used correctly and they dissipate quickly. They have little effect on wildlife. They are accepted for use in organic practices. However, only the insects coated by the oil are killed, so thorough coverage, even of the undersides of branches, is required. Horticulture oils can also kill beneficial insects, if they are present during spraying. Beware — horticulture oils can burn plants if applied improperly. Temperatures should be above 32 degrees and less than 90 degrees. Do not apply if rain is expected. If you choose to spray, use only products specifically recommended for your particular plant; read and follow the label. Do not spray when your fruit trees are in bloom! You will kill bees and other pollinators.

Control codling moths, the cause of wormy fruit, after the flowers drop. Their wormlike larvae cause messy tunnels in apples and pears. When populations are minimal, sanitation is the first step.

UC Davis entomologist Dr. Mary Louise Flint recommends, “Every week or two, beginning about six to eight weeks after bloom, check fruit on trees for signs of damage. Remove and destroy any infested fruit showing the frass-filled holes. Removing infested fruit before the larvae are old enough to crawl out and begin the next generation can be a very effective method for reducing the population. Thinning out the infested fruit has the added benefit of encouraging the remaining fruit on the tree to grow larger.”

Enclosing young fruit in paper bags right on the tree four to six weeks after bloom can prevent the adults from laying eggs on them. Either bag all the fruit, or as many as you think you will need. Check any unbagged fruit regularly for worms and remove from the tree.

For more information, go to

A bit of care now will yield fruit benefits later.

JoAnne Skelly is Associate Professor & Extension Educator, Emerita at University of Nevada Cooperative Extension. She can be reached at


Use the comment form below to begin a discussion about this content.

Sign in to comment