WSU Extension

Hortsense

Pear : Scab
(revision date: 3/10/2017)


Biology
Scab on pear is a fungal disease very similar to apple scab. The disease infects during wet weather in the spring and summer. Lesions appear on leaves, petioles, twigs, and fruit. The spots enlarge and darken, first to dark, velvety, olive-green then to black. Lesions on twigs are first blister-like, later appearing brown and velvety to corky. Infected leaves are often twisted or deformed. Fruit infected early in development shows olive-green to brown spots, which are later russetted and corky, and may have deep cracks. These fruit are often misshapen. Fruit infected at later stages develops small black "pinpoint" scab spots while in storage. The disease is most favored by cool, wet conditions and overwinters in infected fallen leaves and sometimes on twigs. Pear scab does not infect apple, nor are pears susceptible to apple scab.
Management Options

Non-Chemical Management
  • Plant scab-resistant varieties such as 'Buerre Gifard' (immune), 'Conference', 'Doyenne du Comice', and Asian pears (Pyrus serotina and P. ussuriensis).
  • Plant in full sun.
  • Space plantings and prune to provide good air circulation and light penetration.
  • Avoid overhead irrigation.
  • Rake and destroy fallen leaves or cover them with soil. Do not compost infected leaves.
  • Prune out twig infections, when practical.
Select non-chemical management options as your first choice!

Chemical Management

Apply fungicides during delayed dormant period. Make applications at intervals recommended on product labels until weather dries. When in blossom, wait until 3/4 of petals have fallen before making applications. 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.

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.
  • Bonide Fruit Tree & Plant Guard R-T-Spray
    Active ingredient: boscalid, lambda-cyhalothrin, pyraclostrobin  |  EPA reg no: 4-488
  • Hi-Yield Snake Eyes Dusting Wettable Sulfur
    Active ingredient: sulfur  |  EPA reg no: 7401-188-34911
  • Lilly Miller Sulfur Dust Fungicide/Insecticide Dust or Spray
    Active ingredient: sulfur  |  EPA reg no: 802-16
  • Safer Brand Garden Fungicide/Flowers, Fruit & Vegetables Conc
    Active ingredient: sulfur  |  EPA reg no: 42697-37
  • This list may not include all products registered for this use.
Images
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Caption: Scab on pear fruit
Photo by: R.S. Byther
Caption: Scab on pear leaves and twigs
Photo by: R.S. Byther
Caption: Scab on pear twigs
Photo by: R.S. Byther