4 Common Fruit Tree Problems and How to Prevent Them

Have you ever bitten into a worm in your apple or had a poor harvest because of diseases affecting your tree? Fruit trees in Utah suffer from a variety of problems. You’ll learn how to identify and prevent some of the most common fruit tree problems in this post:

Cherry Fruit Fly

Cherry fruit flies are only a fraction (1/5) of an inch long. They have a black body with white stripes and wings with black stripes. The worms you might find in your cherries are usually off-white and close to half an inch long.

Female cherry fruit flies lay their eggs directly under the skin of ripening cherries. After the eggs hatch, larvae travel deep into the cherries to feed until they crawl out of the cherries and drop to the ground 2–3 weeks later. They continue developing in the soil over the winter and emerge as full-grown flies the next spring.

To help determine the number of flies around your trees, place a yellow fly trap sheet in one of your cherry trees. This can help you determine when you need to start treating for fruit flies.

The only truly effective way to prevent cherry fruit flies from laying eggs in your cherries is to spray an insecticide every 2–3 weeks during the growing season. Stewarts usually has success spraying for this pest three times during the season with its special Fruit Tree Program.

Codling Moth

Commonly found in apples and pears, the codling moth can be very damaging to your fruit trees without proper management. Codling moths have gray wings and are about ½ an inch long. The worms of codling moths have dark brown heads with white or light pink bodies. When they bore into fruit, they leave a trail of feces (called frass) behind them.

Similar to cherry fruit flies, female codling moths lay their eggs on fruit, leaves, or nuts. After hatching, larvae enter fruit to continue developing. They enter the next phase of their lifecycle after hiding in the soil or in cracks on the tree bark through the winter.

In mid-March and April, adult moths emerge from their hiding places and are usually active in the early morning and late in the evening.

The best way to treat for codling moth is to use a pesticide every 2–3 weeks throughout the growing season (about 6 times a year). A few other options for controlling codling moth are the following:

  • Bag the fruit while it’s still on the tree
  • Check fruit each week for signs of damage and remove all infested fruit (this can help reduce the number of moths that make it to adulthood)
  • Clean up dropped fruit as soon as it falls
  • Hang multiple traps high in your tree to reduce the number of adult moths (this won’t prevent current damage, but may help prevent future damage)

If your trees have a large infestation of codling moth, pesticides will be most effective in the long run. Pesticides can’t kill larvae that are inside the fruit, so multiple sprays will be necessary to control the moths.

Shot Hole Fungus

Shot hole fungus (also referred to as coryneum blight) starts by creating small light yellow and green spots on leaves that eventually turn brown or black and create small holes. The fungus can also cause small bumps on branches and rough discolored spots on fruit.

The fungus is spread by wind and rain that carries spores to trees. The fungus can live in infected branches and buds during the winter months and spread during the spring. Shot hole fungus thrives in rainy conditions—spores need consistently wet conditions in order to infect trees that they land on.

To prevent your fruit trees from becoming infected with shot hole fungus do the following:

  • Prevent the foliage of your tree from becoming and staying wet for long periods of time by using sprinklers that stay low to the ground and by pruning lower branches
  • Prune off infected branches promptly
  • In fall, prune any branches and buds that look infected
  • Apply a fungicide spray to keep the disease away

Fire Blight Bacteria

A variety of trees—including apple, crabapple, and pear trees—are affected by fire blight. Fire blight bacteria cause blossoms and twigs to wilt and appear scorched.

Sometimes the disease forms cankers on branches and fruit that ooze red or yellow liquid. When it spreads, the disease causes inner bark to develop pinkish-red lines; eventually, infected wood dries out and dies.

Fire blight survives in small growths on branches and tree trunks during the winter months and is spread by insects and rainwater in the spring. It usually infects blossoms and thrives in rainy, warm conditions.

This disease is difficult to eradicate once it infects a tree, but you can do the following to help treat it:

  • Prune infected branches 8–12 inches below all cankers
  • Disinfect pruning equipment with alcohol or bleach between every cut
  • Apply a dormant oil with copper spray in early spring
  • Apply a disease injection in the late spring


Stewart’s specialized fruit tree treatments start in May. Call 801-226-2261 and ask to speak with a specialist today about getting quality treatments and a free service quote for your trees!