Rust is one of the most common fungal diseases of garden plants, there are thousands of different species 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, beans and soybeans, 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:
- 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 them into the garden.
- 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.
Learn more about managing rusts here.