How to Get Rid of Powdery Mildew on a Peach Tree

Prune your tree well during dormancy to open the canopy. Remove any branches that cross or touch other branches and focus on thinning the center of the tree's canopy. Promote air circulation with regular pruning to keep the humidity level inside the canopy low in order to destroy powdery mildew spores as they develop.

Mix neem oil at a rate of 2 tablespoons per gallon of water in a spray applicator in the late spring or early summer, when the first signs of disease are visible. Watch for white, powdery growth to appear on leaf surfaces before you begin your spray treatment. Spray your tree thoroughly when the temperature is below 90 degrees Fahrenheit, making sure to coat buds and young fruits.

Reapply neem oil to your tree weekly until all signs of powdery mildew are gone. Prevent reinfection by spraying the tree on a 14-day schedule, making sure to wet both sides of leaves as well as tender stems each time. Remove any water sprouts that shoot up between treatments -- these tiny peach branches can harbor powdery mildew spores between seasons.

Clean up the area around your peach tree well at the end of the season. Remove all fruits that haven't fallen, rake leaves and prune excess growth at this time. This will help prevent future infections of powdery mildew, as well as a host of other fungal diseases.