Showy, versatile cherry trees (Prunus spp.) play a dual role gardens as an ornamental tree and a fruit crop. Both sweet cherries (Prunus avium) and sour cherries (Prunus cerasus) provide fragrant blossoms in spring and edible fruit in late summer -- and both are susceptible to the same pests. Pests rarely cause serious damage to healthy cherry trees, although some can decimate entire crops and must be eliminated.
Sweet cherries thrive in U.S. Department of Agriculture plant hardiness zones 5 to 7, while sour cherries grow best in USDA zones 4 to 6.
Most cherry trees will attract insect pests at one point or another. Although most are relatively benign, some pose a more serious threat.
Spider mites overwinter in leaf matter around the base of cherry trees, then emerge in summer during hot weather. Although small colonies of spider mites can be safely ignored, larger outbreaks can cause problems for younger cherry trees. Signs of infestation include:
- Yellowish stippling on leaves
- White, silky web-like matter that increases in density when mite populations are high
Treat infestations by spraying the tree with commercially prepared insecticidal soap every five to seven days until the problem subsides.
Black Cherry Aphids
Black cherry aphids pose a low to moderate risk to cherry trees when they feed on the tree’s sap. Smaller colonies can be ignored, although advanced infestations can cause stunted growth in young trees. Signs of infestations include:
- Black sooty residue on foliage
- Sticky or curled leaves
Pear sawfly larvae resemble slimy, dark green slugs. They feed on the leaf epidermis, creating a lacy appearance on the foliage. Their damage is cosmetic and they don't require treatment. Look for:
- Skeletonized leaves
- Visible “slugs” on the leaves
Western Cherry Fruit Fly
One common and serious insect pest that plagues cherry trees is the western cherry fruit fly. These flying pests lay their eggs in developing fruit, and those mature into maggots that render the fruit inedible. Signs of an infestation don’t appear until after the fruit has ripened and is already damaged, so watch for adult western cherry fruit flies early on. They are fly-like insects with distinctively striped wings.
Apply a commercially prepared spinosad- or carbaryl-based insecticide to the host tree every seven days starting when the fruit has developed a salmon-pink blush. Cultural controls such as mulch or grass over the tree's root zone will prevent the larvae from entering the soil, which will impede their life cycle.
Wear protective gear such as gloves, goggles, long sleeves and a face mask when working with insecticides.
Birds and Other Pests
Birds and animal pests such as raccoons often plague cherry trees, feasting on the fruit throughout the growing season. Both can be controlled using nonlethal and humane measures such as barriers.
The best method for dissuading birds from pecking cherries is to cover the tree with bird netting. Cover the tree early in the season after pollination but before the first damage appears. Drape netting over the entire canopy, then gather the open end together and secure it around the trunk with rope or twist ties.
Larger cherry trees may be too large to cover with netting. To reduce the amount of effected fruit, hang shiny or noisy items such as disposable pie pans, old CDs or mylar balloons to the tree to scare the birds off.
A determined raccoon will almost always find a way to pilfer cherries, but you can reduce their impact by making access to the tree's canopy more difficult. The best way to dissuade raccoons is to install a heavy plastic or metal barrier around the trunk. Use a 24-inch-long galvanized stove or vent pipe sliced lengthwise down one side to wrap around the trunk. Alternatively, install motion lights and play a radio near the tree to scare the hungry rascals away.
Raccoons will still climb into trees if they have other access points such as from a rooftop or neighboring tree.