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Cedar-apple Rust Gall This fungus has the fancy name, Gymnosporangium juniperi-virginianae, which means  "naked spore-bearer of the eastern juniper tree." It's a heteroecious rust, which means that it requires two species of plants to complete its life cycle.  Those two species of plants are: the eastern red cedar (Juniperus virginianus) and apple trees (Malus sylvestris). It's also an obligate pathogen, so it can't live without those hosts.  It has four different stages, the most impressive of which is the orange teliospore stage because this is when the gall sprouts gelatinous, orange horns that look like tentacles. Pretty impressive. To further add to its coolness, each gelatinous spore horn is actually composed of hundreds of two-celled teliospores.  Neat-o.  The round, brown galls (pictured)  sprout the gelatinous spore horns during the spring. I'll be revisiting this location in hopes of spotting some orange horns. Cedar-apple Rust Gall,Geotagged,Gymnosporangium juniperi-virginianae,Spring,United States,cedar gall,cedar-apple rust,gall Click/tap to enlarge Promoted

Cedar-apple Rust Gall

This fungus has the fancy name, Gymnosporangium juniperi-virginianae, which means "naked spore-bearer of the eastern juniper tree." It's a heteroecious rust, which means that it requires two species of plants to complete its life cycle. Those two species of plants are: the eastern red cedar (Juniperus virginianus) and apple trees (Malus sylvestris). It's also an obligate pathogen, so it can't live without those hosts. It has four different stages, the most impressive of which is the orange teliospore stage because this is when the gall sprouts gelatinous, orange horns that look like tentacles. Pretty impressive. To further add to its coolness, each gelatinous spore horn is actually composed of hundreds of two-celled teliospores. Neat-o. The round, brown galls (pictured) sprout the gelatinous spore horns during the spring. I'll be revisiting this location in hopes of spotting some orange horns.

    comments (3)

  1. This image from Wikipedia shows what the orange horns look like:

    https://en.wikipedia.org/wiki/Gymnosporangium_juniperi-virginianae#/media/File:Cedar-apple_rust_2.jpg
    Posted 7 years ago, modified 7 years ago
  2. Absolutely fascinating. I must admit that galls still mostly go above my understanding. Posted 7 years ago
    1. Agreed. Pretty crazy to be an obligate pathogen that requires two hosts. So many factors need to work out for it to survive and reproduce. Posted 7 years ago

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"Gymnosporangium juniperi-virginianae" is a plant pathogen that causes cedar-apple rust. In virtually any location where apples or crabapples and Eastern red-cedar coexist, cedar apple rust can be a destructive or disfiguring disease on both the apples and cedars. Quince and hawthorn are the most common host and many species of juniper can substitute for the Eastern red cedars.

Similar species: Pucciniales
Species identified by Christine Young
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By Christine Young

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Uploaded Apr 19, 2018. Captured Apr 14, 2018 13:51 in 3280 Franklin Ave, Millbrook, NY 12545, USA.
  • Canon EOS 80D
  • f/2.8
  • 1/166s
  • ISO100
  • 100mm