DiseaseMedium Severity

Crab Apple Scab

Venturia inequalis, V. asperata

A fungal disease affecting apple, crabapple, pear, and related species throughout North America and Europe. Cool, wet weather favors severe infections that can cause significant defoliation and reduce tree aesthetic value.

Peak Season: Primary infection: Spring rain periods (April-June)Spore release: During wet weather in springSymptom appearance: 9-17 days after infectionSecondary spread: Throughout summer via splashing rainOverwintering: In fallen infected leaves
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Crab apple scab showing characteristic olive-green lesions and leaf spots

Identification & Symptoms

What to Look For

Small, velvety, olive-green spots on lower leaf surfaces
Lesions with unclear margins that become more distinct with age
Some crabapple infections may appear reddish in color
Lesions more numerous near leaf mid-veins
Leaf distortion in heavily infected specimens
Premature leaf drop during summer
Severe defoliation by mid-to-late summer

Potential Damage

Early defoliation reducing tree vigor
Aesthetic damage from leaf spotting and drop
Reduced photosynthetic capacity
Weakened trees more susceptible to other stresses
Economic losses in commercial orchards
Reduced fruit quality in affected trees

Lifecycle

Fungus overwinters in fallen diseased leaves. In spring, airborne spores are produced during rain periods from April to June. Spores are wind-carried to young leaves and fruits. After germinating in water films, symptoms appear in 9-17 days. Secondary spores spread by splashing rain continue infections throughout summer.

Professional Treatment Approach

1

Fungisol applications before and during spring spore release periods

2

Preventive treatments starting at bud break

3

Multiple applications during wet spring weather

4

Remove and destroy fallen leaves to reduce overwintering inoculum

5

Improve air circulation around susceptible trees

Recommended Mauget Products

Fungisol

Professional-grade treatment specifically effective against crab apple scab.

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