Gymnosporangium rusts are sporulating now on Juniperus hosts. Look for orange, gelatinous structures on foliage and stems of various Juniperus spp. They are sporulating both in container production and in the field. They can be found sporulating when the Cercis canadensis (redbud) begin to bloom, unless it is too dry.
Monitor for Gymnosporangium rusts such as Cedar-apple rust (above)
Cedar-Hawthorn Rust (above)
Cedar-Quince rust (above)
and Pear Trellis Rust (above) on Juniperus.
Their spores spread by wind and rain for several km. Protect Rosaceous hosts (e.g. Pyrus, Amelanchier, Malus, Crataegus etc.) before rain or irrigation events with fungicides such as Nova, Pristine, Daconil or Dithane.
To help prevent unsightly Gymnosporangium rusts on Malus (above), Crataegus Amelanchier and Pyrus this summer.
Cedar-Quince rust on Amelanchier fruit, July.
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