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Monitor Shoot Strikes in Spring

Shoots that have been mined by peach twig borer or oriental fruit moth larvae can cause the affected portion of the twig to wilt—a symptom known as "flagging" or a "shoot strike." Monitor for shoots infested with peach twig borer and oriental fruit moth by looking for shoot strikes.

To monitor for shoot strikes:

  1. Start looking for shoot strikes or flags in the orchard in mid-April.
  2. Walk through the orchard and cut down any shoot strikes you see.
  3. Slice these shoots open and look for larvae.
  4. Determine if peach twig borer or oriental fruit moth caused the strike. If it is not difficult to find four or more shoot strikes per tree in a mature orchard, you may need to consider a control action.
Shoot terminal mined by peach twig borer.
Peach twig borer strike
Shoot strike caused by oriental fruit moth.
Oriental fruit moth strike

Mature larva of peach twig borer.
Peach twig borer larva
Identification tip:
When they first hatch, peach twig borer larvae are light brown with a black head and prothorax. As they grow, the head and prothorax remain black, but the body turns chocolate brown and white portions between each body segment give the appearance of bands.

Identification tip: Shoot strikes are the wilting of a terminal shoot tip. Leaves are limp and sag. Peach twig borer and oriental fruit strikes look the same. Open shoot up and check for the caterpillar.
Oriental fruit moth larva inside damaged shoot tip.
Oriental fruit moth larva
Identification tip: The oriental fruit moth larvae are white or pink with a brown head. A feature that distinguishes it from other larvae such as the navel orangeworm and peach twig borer is an anal comb that protrudes from beneath the sclerite of the last abdominal segment.

Related information

Statewide IPM Program, Agriculture and Natural Resources, University of California
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