Tuesday, June 30, 2009

Petal Blight in Rhododendron spp.



The buds and flower is the only part affected by this fungal disease. Humid conditions favour the spread of this fungus, which initially starts as small circular spots that quickly enlarge into irregular blotches.
Affected flowers dry out and turn brown and papery. They remain stuck to the plant for some weeks, unlike healthy flowers which would fall from the bush once faded. Grey mould can look similar and only affects petals.
The specific fungus particularly affects Kurume and Indica azaleas.
Control by collecting and destroying dead and diseased flowers, but spores can blow from plants considerable distance away. Spray with triadimefon as soon as buds show colour in humid weather if severe infection.

Reference : Judy McMaugh, pg 269

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