Apricot Pests - The Backyard Orchard

Published by Utah State University Extension and Utah Plant Pest Diagnostic Laboratory

January 2011

IPM-007-11

Coryneum Blight (Shothole)

IMPORTANCE AS A PEST ON APPLE: high

OTHER FRUIT HOSTS: nectarine, peach, and sometimes cherry

SYMPTOMS:

• round, corky or sunken spots on fruit
• dead twigs
• holes in leaves
• dead buds that ooze gum

GENERAL INFO:

Shothole is a common fungal disease in Utah. It attacks dormant leaf buds, blossom buds, leaves, fruit, and twigs. The first visible lesions occur on young leaves as small, round, tan spots that eventually fall out, leaving round holes. Circular lesions develop on fruit that first appear as reddish spots, and later as rough, corky bumps. Apricots are very susceptible.

MANAGEMENT:

Prune and destroy all infected plant tissue. Prevent irrigation water from wetting leaves. For severe infections, apply copper spray in fall starting at 50% leaf drop to protect newly forming buds.

Gummosis

IMPORTANCE AS A PEST ON APPLE: moderate

OTHER FRUIT HOSTS: all stone fruits

SYMPTOMS:

• gelatinous-like ooze on bark

GENERAL INFO:

Gummosis is a general term describing the prolific oozing of clear sap from beneath the bark. Gumming is produced in response to a variety of conditions, including insects, diseases, and wounding. It can also be a response to poor growing conditions, such as compacted soil.

MANAGEMENT:

To most accurately identify the cause of gummosis, consult your local Extension agent.

Perennial Canker

IMPORTANCE AS A PEST ON APPLE: moderate

OTHER FRUIT HOSTS: cherry, nectarine, peach and plum

SYMPTOMS:

• amber-colored ooze
• flaking bark
• necrotic (brown) cambial tissue just under the bark interveinal chlorosis (yellowing between veins)

GENERAL INFO:

Also called cytospora canker, perennial canker is caused by a fungus. Cankers are areas of dead cambium and bark and can occur on stems, limbs, and twigs. They are off-color, usually oval-shaped, and usually slightly sunken. Dark amber gum may exude from the canker edges. Cankers enlarge yearly or advance down side branches. Spores spread this fungus during wet weather, and successful infections occur in weak or wounded tissue.

MANAGEMENT:

Prune out diseased tissue, prevent wounding, and keep trees healthy. There are no fungicides for managing cankers.

Greater Peachtree (Crown) Borer

IMPORTANCE AS A PEST ON APPLE: moderate

OTHER FRUIT HOSTS: nectarine, peach, and plum

SYMPTOMS:

• ooze mixed with sawdust-like frass at the soil line
• dieback of canopy

GENERAL INFO:

The larval form of this clearwing moth damage trees by tunneling in the cambium, just below the bark, typically at the soil-line of the trunk. Backyard orchardists should look carefully for round holes near the soil-line and oozing tree sap mixed with frass (sawdust-like excrement, shown at right). Adult moths begin activity in late June and mated females lay their eggs on the base of tree trunks or upper roots. Trees may be girdled and die due to borer injury. Young trees and old or drought-stressed trees are vulnerable.

MANAGEMENT:

Preventive trunk sprays with permethrin or carbaryl are the main control tactic, starting in late June, and continuing every 2 - 3 weeks through September. Only spray lower 12 - 18” of trunk and exposed roots.

Peach Twig Borer

IMPORTANCE AS A PEST ON APPLE: moderate

OTHER FRUIT HOSTS: nectarine, peach, and plum

SYMPTOMS:

• frass (sawdust-like excrement) on fruit
• holes in fruit
• dead shoots

GENERAL INFO:

In spring, chocolate brown larvae emerge from overwintering cells on the limbs of trees and then tunnel into succulent shoot tips. Infested twigs die back and small amounts of gum may exude from tunnel openings. In summer, a second generation of these “worms” enters fruit when succulent shoot growth has ceased. In backyard trees, injury may not be severe enough to require treatment every year.

MANAGEMENT:

Twig borer activity is strongly regulated by temperature and insecticide timing varies from year to year. To find out when peach twig borer is active in your area of the state and for when to spray, contact your local county Extension agent, or subscribe to the USU IPM Tree Fruit Advisory. Insecticides like spinosad, carbaryl, and malathion work for peach twig borer.

Spider Mites

IMPORTANCE AS A PEST ON APPLE: moderate

OTHER FRUIT HOSTS: all fruits

SYMPTOMS:

• stippled leaves
• loss of tree vigor
• fine silk webbing that becomes apparent when populations are high

GENERAL INFO:

Mites are very small arthropods that are more closely related to ticks than insects. Spider mites overwinter as adults at the base of trees and may become a problem during hot, dry conditions in mid and late summer when they reproduce rapidly (1-2 weeks to complete a generation). They remove chlorophyll from leaves, causing a stippling appearance.

MANAGEMENT:

Low populations of spider mites can be ignored and are often kept in check by predatory mites. Spider mite outbreaks often follow pesticide applications that upset the predator-prey balance. If necessary, apply insecticidal soap or horticultural mineral oil every 5-7 days. Avoid applying soaps or oils at temperatures > 80°F as some leaf burn may result.

Earwigs

IMPORTANCE AS A PEST ON APPLE: low

OTHER FRUIT HOSTS: all fruits, but especially stone fruits and berries

SYMPTOMS:

• shallow or deep holes in fruit
• black dots of excrement around feeding sites

GENERAL INFO:

Earwigs will climb the apricot trunk and chew into fruits as they near maturity. They also feed on other insects so their presence, at times other than when fruits are ripe, is beneficial.

MANAGEMENT:

Earwigs crawl up tree trunks. Remove debris and weeds from the base of trees. Rolled cardboard strips tucked into limb crotches can be used to trap and remove earwigs from trees (remove and replace cardboard rolls). Exclude earwigs by wrapping the trunk with a 3” wide band of duct tape covered with tanglefoot (a sticky substance). If necessary, carbaryl and spinosad provide a short interval of protection.

European Fruit Lecanium Scale

IMPORTANCE AS A PEST ON APPLE: low

OTHER FRUIT HOSTS: all fruit trees

SYMPTOMS:

• slow tree growth
• yellowed leaves; leaf drop
• honeydew
• twig dieback

GENERAL INFO:

Lecanium scale is a soft scale that has piercing-sucking mouthparts that remove plant phloem or sap. In early summer, thousands of young scales called “crawlers” emerge from under the mother scales and move to new sites to feed. Lecanium scale can build to large populations quickly if not managed. The crawler stage occurs from early July to mid-August in northern Utah.

MANAGEMENT:

Scrub infested limbs with a mesh dish sponge to remove adults. Natural enemies will help regulate soft scale populations. Apply a 2% oil application when apricot buds start swelling in early spring, and apply 1% oil or insecticidal soap in early July on crawlers.

European Paper Wasp, Yellow Jackets

IMPORTANCE AS A PEST ON APPLE: low

OTHER FRUIT HOSTS: soft ripe fruit

SYMPTOMS:

• holes in fruit

GENERAL INFO:

The European paper wasp builds umbrella-shaped nests in protected sites and yellow jackets build nests underground. The European paper wasp is very attracted to soft ripe fruit.

MANAGEMENT:

Clean up rotting fruit on the ground and regularly pick ripe fruit. To trap European paper wasps, cut the top third of a soda bottle off and invert it into the bottom portion. Punch holes along the top edges and insert wires for hanging. Fill the bottle with 1 part fruit juice, 10 parts water, and 1 tsp detergent. Hang the trap in apricot trees or nearby areas just before fruit starts to ripen.