Answer: Apples are subject to any number of foliar problems due to both insect and disease, and some varieties are more susceptible than others. Most home orchardists find it necessary to follow a routine preventive spray program of some sort in order to keep their trees healthy. The potential problems depend on the built-in susceptibilities and resistances of the varieties you grow, the prevalence of certain problems in your local area, and the weather each year. The timing for the treatment(s) is usually critical and may begin in mid winter for certain diseases and pests. I would suggest you contact your local county extension office for a specific diagnosis and steps to take now (if any) and the suggested routine for the varieties you are growing. In the meantime, be sure to clean up and remove and destroy any fallen leaves, twigs or fruit both during the season and this fall to try to limit reinfection.
Best wishes with your tree!
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