Which two diseases are concerns for apples in Wisconsin?

Which two diseases are concerns for apples in Wisconsin?

• A. Powdery mildew and rust
• B. Late blight and downy mildew
• C. Botrytis and brown rot
• D. Apple scab and Fire blight

Answer: (D)

Two diseases that are consistently concerns for apples in Wisconsin are apple scab and fire blight. Apple scab, caused by Venturia inaequalis, shows up in wet springs as olive-green to black lesions on leaves and brown, scabby spots on fruit. It undermines fruit quality and can cause leaf drop, and the fungus survives in fallen leaves, so good sanitation—raking and destroying leaf litter—helps reduce pressure. In addition, protective fungicide timing from bloom through leaf expansion and choosing resistant varieties are effective management tools in our climate.

Fire blight, caused by Erwinia amylovora, tends to appear during warm, wet springs with rapid disease spread. Blossoms can wilt and turn brown or black, shoots and branches may bend into a shepherd’s crook, and cankers can form on limbs. Management centers on sanitation—pruning out infected wood well below the visible symptoms during dry weather and removing infected plant material—and applying appropriate protective sprays during bloom in high-risk years.

Other listed diseases can occur on apples, but they are either less common or less problematic in Wisconsin compared with these two, which is why they’re the primary concerns here.