Blackspot, fringed black spots on leaves, is a fungus disease that can defoliate a plant. Rusts are orange-yellow to rusty brown fungi that attack many plants. Powdery pustules appear on the undersides of leaves, but the first sign of infestation may be a yellow mottling on the upper leaf surfaces.

Commercial product: Lime sulfur (calcium polysulfide); effective against powdery mildews and rusts
Home remedy: Baking soda spray (mix 1 teaspoon baking soda and 1 teaspoon horticultural oil in 1 gallon of water); effective against blackspot and powdery mildews

Gentle pest controls