DiseaseMedium Severity

Apple Scab

Venturia inequalis, V. asperata

A fungal disease that causes olive-green to dark spots on leaves and fruit of apple, crabapple, and related species. The disease is favored by cool, wet weather and can cause severe defoliation of susceptible varieties.

Peak Season: Primary infection occurs in spring (April-June) during cool, wet weather. Secondary infections continue throughout summer during rainy periods.
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Apple scab fungal lesions on leaves showing characteristic dark spots

Identification & Symptoms

What to Look For

Small, velvety, olive-green spots on lower leaf surface initially
Lesions become darker and more distinct with age
Unclear margins on young lesions
Some crabapple infections may be reddish in color
Lesions more numerous near mid-vein of leaf
Leaf distortion in heavy infections
Early summer leaf drop
Severe defoliation possible by mid-to-late summer

Potential Damage

Reduced photosynthetic capacity from leaf spots
Premature defoliation weakens trees
Reduced fruit quality and yield
Tree stress and reduced vigor
Aesthetic damage to ornamental trees
Increased susceptibility to other problems

Lifecycle

The fungus survives winter in fallen diseased leaves from the previous year. In spring, it produces airborne spores during rain periods from April through June. Spores are wind-carried to young leaves, flowers, and fruits. After germination and penetration, symptoms appear in 9-17 days. The fungus then produces additional spores that spread via splashing rain throughout the summer.

Professional Treatment Approach

1

Fungicide applications during spring infection period

2

Remove fallen leaves to reduce inoculum

3

Improve air circulation through pruning

4

Plant resistant varieties when possible

5

Preventive fungicide programs for susceptible trees

Recommended Mauget Products

Fungisol (Propiconazole)

Professional-grade treatment specifically effective against apple scab.

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Tebuject-16 (Tebuconazole)

Professional-grade treatment specifically effective against apple scab.

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Arborfos (Potassium phosphite)

Professional-grade treatment specifically effective against apple scab.

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