Gall rust found on Scots pines

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.  

On Scots pine, gall rust can be found on branches and on the main trunk. Infection begins when spores infect green, succulent stems during wet springs. Symptoms rarely appear the year of infection, but galls on the twigs near the point of infection appear in subsequent years. The conspicuous, perennial, round-stem galls can be one to four inches-plus in size. The galls are now beginning to turn yellow-orange due to the release of spores. This rust disfigures and severely reduces the tree quality. Pruning out these galls before they produce spores may help to reduce the spread of this rust. We have not seen much of any control when growers have tried to use fungicides.

Gall rust

Photo 1. Gall rust just beginning to turn orange.

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