Cedar-Apple Rust
As I was strolling through the crabapple fields in Wooster at Secrest Arboretum, I began to notice that something was significantly different than the last time that I had evaluated the trees. Since I was evaluating the trees for apple scab, it suddenly struck me that I was also looking at a lot of polka-dot covered trees! What in the world was going on? As I looked closer at the foliage, the thing that stood out the most were the number of yellow-orange dots.
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Our wet weather this spring has triggered spectacular spore production by three types of rust fungi on junipers in southwest Ohio. All three fungi belong to the genus Gymnosporangium and each must alternate between a member of the plant genus Juniperus and members of the rose family (Rosaceae) in order to complete their life cycle. The requirement to cycle between two types of widely divergent host plants coupled with the rusty color of their spores earns these fungi the collective moniker of "heteroecious" rusts.
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