What happens when you combine mild weather, a rain that lasts for a day or two and rapidly growing plants fighting for space? Nature has provided perfect growing conditions for the disease rust.
One of the most common fungal diseases of garden plants, there are thousands of different species of rust that infect trees, shrubs, ferns, perennials, edibles and more, like pear, peach, and pine, rhododendrons, roses, chrysanthemums, fuchsias, geraniums, lilies, and snapdragons. Rusts have been a scourge to humans for centuries, impacting important food and fiber crops like grains, bean and soybean, asparagus, cotton, apple, and even coffee. Besides being unsightly, they can reduce plant vigor and in extreme cases, even kill the plant.
Many rusts have minimal effect on plant health, but certain rusts can kill their hosts. Infected foliage on broadleaf plants may become spotted, turn yellow or brown, and drop prematurely. Severe rust on peach trees can cause defoliation and reduce yield. Fruit may display small, sunken dark lesions that split open by the time the fruit is ripe.
Rusts requires free water to reproduce so rainy weather, heavy overnight dew, or overhead watering that wets foliage without enough time to dry produce optimum conditions for this disease, especially with temperatures at 65–70 degrees F. Infection is spread primarily by windblown or water-splashed spores that have survived over the winter.
To prevent rust from getting established in your yard:
Keep it out: Choose disease resistant varieties – check seed catalogs, seed packages, and plant labels for resistance information. Before buying plants, look closely at the inner and lower leaves to confirm they are disease free before bringing into the garden.
Provide excellent cultural conditions: Locate plants so they receive plenty of sunlight with lots of air circulation (don’t crowd them). Maintain healthy soil, and avoid excess nitrogen that results in soft, lush growth.
Manage moisture: Avoid overhead watering, or if necessary, do it early in the day to allow time for leaves to dry quickly. Use drip irrigation or a soaker hose to apply water to the soil, not the leaves.
Keep it clean: Pinch off rust infected leaves and remove them from the garden. Remove and destroy infected twigs, buds, and fruit as soon as symptoms appear. Collect fallen, infected leaves and needles and dispose of them away from host plants (don’t add them to a compost pile).