Leaf Rust

If you have ever come across a plant or tree that has small circular brown spots on its leaves, then you have encountered the common fungal disease called leaf rust. This disease belongs to a family of fungi that develop on the foliar portion of almost any plant or tree when the conditions are optimal for growth. This order of fungi is called Uredinales.

Leaf rust usually is not a singular fungal infection, but a collection of fungi that grow on the foliar portion of a plant. The most common sign of leaf rust is the development of brown spots on the back side of leaves. While most of the time these spots may appear to be brown, they can also be reddish, white, yellow, orange or black, depending on the type of plant and the rust fungi growing on it.

Leaf rust can infect...

Turf grasses: Blue, bent, rye, fescue, Bermuda

Plants: Roses, beans, wheat, hollyhocks, strawberries, raspberries, tomatoes, cucurbits

Trees: Ash leaf rust is the most prevalent, but other trees like maple or oak can be affected


Wet conditions and high humidity are favorable for the growth of leaf rust fungal spores. This can most often occur during mid-April and onward, depending on the geographic area and summer conditions where you live.


The brown spots that are present on the leaves are actually spores, or tiny bumps called pustules. These are colonies of fungus that cause the telltale colored spots on leaves.


If not treated carefully, leaf rust can damage the photosynthesis capability of a plant and weaken its immune system. Leaves will wilt, curl and fall off as the disease progresses on the plant. It can also become widespread and cause the plant to die, depending on the severity of infection.

Orage spots on leaves, or leaf rust on black raspberry 

Leaf rust on a black raspberry plant
 Photo courtesy of http://plantclinic.cornell.edu
Leaf Rust on Rose Leaves
  A close-up of leaf rust on rose leaves
 Photo courtesy of http://www.ipm.iastate.edu

Brown spots on leaves, or leaf rust on Ash tree

Distinct brown spots of leaf rust on Ash leaf
Leaf Rust Treatment
To treat and prevent the possible spread of leaf rust in your garden use Emerald Mist. A regular application of this natural fertilizer and fungicide can provide exceptional protection against an invading fungal disease such as leaf rust. It also provides vital plant nutrients as well.

Contact Garden Vigor for additional information on our natural gardening products that help grow a better garden.