pear trellis rust

Gymnosporangium sabinae is the fungus that causes pear rust. It has an unusual life cycle because it needs both juniper and pear to develop. On pear leaves, it produces bright orange to red spots that are often very striking. On juniper, it can form swollen infected areas that persist for more than one season. In spring, infected juniper tissue produces orange gelatinous spore masses, and these spores go on to infect pear trees. The disease can reduce photosynthesis and may be especially stressful for young trees.

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