Powdery Mildew
Beginner
This pest affects:
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Scientific name
Podosphaera clandestina
Symptoms
Leaves
- Whitish, feltlike patches
- Newly developed leaves on new shoot growth become progressively smaller, are generally pale in color, and somewhat distorted
- Severely infected leaves curl upward, become brittle with age, and may drop prematurely
- By mid-season, the whitish fungal growth can be seen abundantly growing over the leaves and shoots, sometimes in patches and other times covering most of the new growth
- Small, brown to black, spherical bodies (cleistothecia) appear in the felt-like patches as the season progresses
- Growth of sour cherry trees in the nursery and young orchards is reduced by this disease
- Defoliation on older trees can occur as a result of severe infection
- Primarily a problem on sour cherry in Ontario
Fruit
- Fruit infections are rare in Ontario
- Mildew on green fruit appears as shiny, red blotches often with white fungal growth in the center.
Often confused with
Spray residue - easily visible, more dense than powdery mildew
Period of Activity
Shuck fall through midseason.
Scouting Notes
From shuck fall through midseason, monitor ten terminals on each sample tree (at least 10 tens trees per block) for the presence of white, mycelial growth on young leaves.
Thresholds
A total of one to ten infections and greater than ten infections represent moderate and high risk, respectively.
Advanced
This pest affects:
|
Scientific name
Podosphaera clandestina
Symptoms
Leaves
- Whitish, feltlike patches
- Newly developed leaves on new shoot growth become progressively smaller, are generally pale in color, and somewhat distorted
- Severely infected leaves curl upward, become brittle with age, and may drop prematurely
- By mid-season, the whitish fungal growth can be seen abundantly growing over the leaves and shoots, sometimes in patches and other times covering most of the new growth
- Small, brown to black, spherical bodies (cleistothecia) appear in the felt-like patches as the season progresses
- Growth of sour cherry trees in the nursery and young orchards is reduced by this disease
- Defoliation on older trees can occur as a result of severe infection
- Primarily a problem on sour cherry in Ontario
Fruit
- Fruit infections are rare in Ontario
- Mildew on green fruit appears as shiny, red blotches often with white fungal growth in the center.
Often confused with
Spray residue - easily visible, more dense than powdery mildew
Biology
Powdery mildew of cherry is most important during summers with hot, dry weather. The fungus may overwinter on diseased, fallen leaves, but more commonly in infected buds. When infected buds expand in the spring the new growth becomes completely colonized by the fungus. Conidia of powdery mildew are spread by wind to new leaves and shoots. Warm temperatures without rain, but with sufficient moisture such as high humidity, morning fogs, dews, or intermittent rains, are ideal for rapid increase of the disease. Powdery mildew typically is first seen on the underside of leaves and so orchard scouting is important for initial disease detection. The fungus grows as a white mat on leaf surfaces; continued fungal growth results in spread to upper leaf surfaces. Mildew can cause leaves to become brittle, and these leaves can then be subject to premature drop during harvest.
Period of Activity
Shuck fall through midseason.
Scouting Notes
From shuck fall through midseason, monitor ten terminals on each sample tree (at least 10 tens trees per block) for the presence of white, mycelial growth on young leaves.
Thresholds
A total of one to ten infections and greater than ten infections represent moderate and high risk, respectively.
Management Notes
Prune trees and remove hedgerows close to orchards to facilitate drying of fruit and foliage to create a less favorable microclimate for disease development.
Management with fungicides - Fungicides are sometimes used to control powdery mildew in commercial sour cherry orchards. See OMAFRA Publication 360, Guide to Fruit Production :
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Chapter 7 Sour Cherries or Sour Cherry Calendar only: Recommendations for powdery mildew at First cover, Second cover, Post harvest |
Some information included aboce was excerpted from;
