Apricot: Peach twig borer

Biology

The peach twig borer is an important pest of apricots, particularly in eastern Washington. In the spring, overwintering larvae bore down the center of shoots, causing the tip to wilt or “flag”. Each caterpillar can damage several shoots. Later generations of larvae feed on both shoots and fruit. They often burrow into the stem end of young fruit. Pits of infested fruit are often split. They may also feed on the fruit surface. The caterpillars are reddish-brown with black heads and yellowish rings on the body. Mature caterpillars are up to 1⁄2″ long. The adult moth is dark gray and about 1⁄3″ long. Peach, nectarine, plum and prune may also be attacked.

Management Options

Use Integrated Pest Management (IPM) for successful plant problem management.

Non-chemical Management

Select non-chemical management options as your first choice!

• A tiny wasp parasitizes eggs of the peach twig borer. Avoid use of broad-spectrum insecticides whenever possible to conserve beneficial insects.
• Cut out flagging twigs below the mined portion. Be sure to kill larvae inside.
• Overwintering larvae may be found under thin bark in branch crotches. Look for a buildup of chewed bark and frass (excrement).

Chemical Management

IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides.

• Apply products at bud swell and/or at complete petal fall when later-season larvae bore into twigs, shoots, or fruit.
• NOTE: Esfenvalerate is toxic to bees.
• Do not apply products containing esfenvalerate on or near blooming plants.
• To minimize risk to bees, apply in the evening after bees have stopped foraging for the day.
• Homeowners should not make foliar applications to trees over 10 ft. tall.
• Consult a commercial pesticide applicator for treatment of trees and shrubs over 10 ft. tall.

Approved Pesticides

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.

• Monterey Bug Buster II
  Active ingredient: esfenvalerate [EPA registration number: 1021-1778-54705]
• Monterey Garden Insect Spray [Organic]
  Active ingredient: spinosad (spinosyn A+D) [EPA registration number: 62719-314-54705]
• Natural Guard Spinosad Bagworm, Tent Caterpillar & Chewing Insect Control
  Active ingredient: spinosad (spinosyn A+D) [EPA registration number: 62719-314-7401]
• This list may not include all products registered for this use.

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