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European apple sawfly (EAS)

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Hoplocampa testudinea

Overview

EAS larvae feed under apple skin producing a heavily russetted, winding scar often seen on mature fruit at harvest.

Biology

  • EAS overwinter as mature larvae in the soil. Larvae pupate and adults emerge when apples buds are in Pink stage.
  • Adult EAS are clear winged, fly-like insects about 1/3 inch, dark brown above, and orange to yellow below.
  • After feeding on apple pollen, EAS females cut slit into calyx end of tiny, developing fruit and insert an egg.
  • Newly hatched larvae burrow just under apple skin leaving winding scar. (By harvest this scar is visible as a heavily russetted, winding scar.)
  • If not controlled, larvae migrate to a second fruit and tunnel to the core. Frass can usually be seen on the surface of these apples, which drop to the ground by July. Mature larvae are 1/2 inch long, yellowish-white, and posses a pair of legs on each body segment.
  • Full-grown larvae enter the soil where they remain until the following spring.

Monitoring

  • EAS damage occurs more frequently when bloom time is extended and petal fall insecticide applications are delayed.
  • White sticky traps placed before bloom can help determine the need for EAS insecticide at Petal Fall. Traps should be placed near blossoms at head height on the south side of at least one tree per 3 acres. Insecticide application may be warranted if more than an average of 6-9 EAS per trap are captured by Petal Fall in a block that received prebloom insecticide (or 4-5 in a block that did not receive prebloom insecticide).

Management

  • Generally insecticides applied at Petal Fall adequately control EAS. Insecticide application is directed at early, superficially-burrowing larvae. Since apple varieties enter Petal Fall at different times, separate Petal Fall treatments may be needed.
  • Prebloom insecticide for EAS is not needed except possibly for blocks where Petal Fall insecticide has historically not given satisfactory control.