Orange Gooey Fungus on Trees

Updated November 21, 2016

Tree rust is a common fungus that affects different types of trees. During the third spore stage, commonly known as the uredial stage, rust becomes easily observable with the appearance of urediospores: gooey, orange pustules on the affected area.


In addition to trees, rust infects all kinds of crops and plants. Even with about 4,000 species of rust, each fungus undergoes the same five-stage life cycle. Each kind of rust affects a particular host. For example, western gall rust, also known as pine-pine rust, infects pine trees.


In addition to urediospores, tree rust can cause swelling and sunken cankers on the affected areas. The rust kills affected leaves, pine needles and branches after a while and can eventually kill the entire tree if the main trunk becomes infected.


The use of fungicide to treat tree rust occurs in two stages. Soaking seeds in fungicide before planting can help prevent growth as well as spraying the foliage with fungicide after growth. Using fungicide does not guarantee complete protection, and as a result, pruning infected branches will help stop the fungus from spreading.

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About the Author

Marissa Poulson has been a freelance journalist since 2009. Her arts and entertainment reviews can be found in The Examiner. Poulson holds a Bachelor of Arts in creative writing from Arizona State University.