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Obliquebanded leafroller (OBLR)

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Choristoneura rosaceana

Overview

OBLR attacks mainly apple and occasionally pear, peach, and cherry. Larvae feed on fruit skin, often close to the apple stem or where two apples are in contact. OBLR roll up leaves and hide in these shelters. Injuries occurring early in the season cause pronounced deformations of the fruit and are impossible to differentiate from the damage of green fruitworms. Late season fruit feeding causes small pits in the fruit surface that may go undetected until after long-term storage.

Biology

  • OBLR overwinter as small larvae in  trees. Overwintering larvae become active when trees break dormancy, and they complete their development about 3 weeks after Bloom. Larvae are yellowish green to olive green; head and thoracic shield vary from tan to brown or blackish.
  • Adults begin to emerge in late May or early June. Adult wings are beige, tinged with red. Forewings are crossed with oblique brown bands.
  • Females can lay up to 900 eggs during a 7- to 8-day oviposition period. Eggs are green and deposited in a mass on upper leaf surfaces.
  • Eggs hatch in about 10 to 12 days. Newly hatched first generation (summer) larvae move to and feed on tender growing terminals, watersprouts, or developing fruit. As these larvae reach the third instar, they display an increasing propensity to damage fruit. This generation takes almost two months to complete development.
  • Adult flight of the second generation occurs in August, and the subsequent larvae hatch in August and September. The second-generation larvae feed primarily on leaves until they enter diapause, although they may occasionally damage fruit. Young larvae construct hibernation sites on twigs or bark to spend the winter.

Monitoring

  • Scout for larval shelters during Bloom to Petal Fall. Examine 10 bud clusters per tree for  OBLR larvae and apply Bt insecticide if find more than 3% infested clusters.
  • Monitor OBLR adults with pheromone traps and use a degree-day developmental model to time insecticide sprays against hatching larvae.

Management

  • A Petal Fall treatment with an insecticide effective on mid-sized to large larvae should control overwintered larvae.
  • Using date of first OBLR capture as a biofix, use degree-day model to determine when OBLR eggs are hatching and most susceptible to insecticide. Apply insecticide starting at 360 DD (base 43F) after 1st adult trap capture. May need 2-3 sprays 10-14 days apart.
  • Thinning of fruit and pruning water sprouts in midsummer is helpful in reducing fruit damage.
  • OBLR may be difficult to control with insecticides, even with selective insecticides (Bacillus thuringiensis and insect growth regulators). Selective pesticides will preserve important natural enemies. More than one spray may be needed during the summer because of this species' extended flight and egg-laying periods.