WSU Extension


Bacterial blight 
Eastern filbert blight 
Powdery mildew 
Apple mealybug 
Brown marmorated stink bug 
Filbert aphid 
Filbert bud mite 
Filbert leafroller 
Lecanium scale 
Omnivorous leaftier 
Tent caterpillars 

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Caption: Filbert bacterial blight
Photo by: Unknown
Filbert : Bacterial blight
(revision date: 4/11/2018)

Bacterial blight of filbert may attack buds, leaves, twigs, branches, and the trunk. Infected buds may be killed before leafing out. Leaves initially develop pale green, water-soaked spots, which later turn reddish-brown. Current-season shoots show dark green, water-soaked spots on the bark. These later turn reddish-brown and can girdle the stem, causing dieback above the lesion. Leaves often remain attached to dead shoots. One- and two-year-old twigs are also attacked. Infections may spread into main branches or trunks, where cankers may girdle and kill trees. The infected tissues may show a bacterial ooze in the spring, when most new infections occur. Bacterial blight is more severe on trees that have been damaged by frost, sunscald, or other problems.
Management Options

Non-Chemical Management
  • Plant disease-free stock.
  • Plant resistant varieties such as 'Hall's Giant'.
  • Avoid highly susceptible varieties such as 'Barcelona'.
  • Provide proper culture. Healthy trees are more resistant to disease.
  • Prune out and destroy infected tissues, making cuts 2'-3' below infected branches. Disinfect pruning tools between cuts to avoid spreading bacteria to healthy tissues.
  • Prevent injury to trees including sunscald and frost damage, if possible.
Select non-chemical management options as your first choice!

Chemical Management

Apply in late August or early September. In seasons of heavy rainfall, apply again when 3/4 of the leaves have dropped. 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.
  • Monterey Liqui-Cop Copper Fungicidal Garden Spray
    Active ingredient: copper-ammonia complex  |  EPA reg no: 54705-7
  • This list may not include all products registered for this use.

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Caption: Filbert bacterial blight
Photo by: Unknown