Pear: Scab

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

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

Non-chemical Management

Select non-chemical management options as your first choice!

• 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.

Chemical Management

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

• 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.

Approved Pesticides

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

• Bonide Fruit Tree and Plant Guard R-T-Spray
  Active ingredient: boscalid, lambda-cyhalothrin, pyraclostrobin [EPA registration number: 4-488]
• Hi-Yield Snake Eyes Dusting Wettable Sulfur
  Active ingredient: sulfur [EPA registration number: 7401-188-34911]
• Lilly Miller Sulfur Dust Fungicide/Insecticide Dust or Spray
  Active ingredient: sulfur [EPA registration number: 802-16]
• Safer Brand Garden Fungicide/Flowers, Fruit and Vegetables Concentrate
  Active ingredient: sulfur [EPA registration number: 42697-37]
• This list may not include all products registered for this use.

Additional Images