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Apple Scab Info / Symptoms:

If you have a flowering crabapple or fruit-bearing apple tree that flowers and leaves out fully in the spring but then starts shedding its leaves in the early summer, your tree may have apple scab.  Although apple scab is not fatal in and of itself, it can weaken your tree to the point that more serious diseases or insects will take over.  Since scab causes your tree to shed its leaves prematurely, it loses the ability to generate food for itself. If your tree has shed one third or more of its leaves early the last couple of years, you should initiate some disease control practice.

Control Methods:

Control of this disease involves three steps. The first step is sanitation; the spore that infects this year’s foliage over winters in last year’s fallen leaves.  Therefore, it is very important that you rake up and dispose of fallen leaves.  The second step you should take to avoid apple scab is to apply a preventive fungicide to the leaves when they are emerging in the early spring. The final step is to fertilize your tree with a general-purpose organic fertilizer such as ESPOMA Plant-tone™ or Tree Tone™ products. ESPOMA Tree Tone™ is a 6-3-2 fertilizer and can be applied in the spring and /or fall. 

Bonide Infuse™ Systemic Disease Control is the fungicide that we recommend using for the treatment of Apple Scab. It is available in a ready to spray (attach to the hose) container. See chart below for timing and frequency recommendations. 

Application #1 Application #2
Buds break & leaves are approximately 1/3 their mature size 7-10 days after initial application
Application #3 Application #4
7-10 days after second application 7-10 days after third application

Check out Matt’s video on how to identify and treat Apple Scab

Photo of Apple Scab from University of Minnesota Extension