PPDL Picture of the Week
February 11, 2018
Rose Botrytis Blight
Tom Creswell, Director, Purdue Plant and Pest Diagnostic Laboratory
Are those beautiful red roses you got for St. Valentine’s
Day drooping sooner than expected?
(Fig. 1) Don’t blame yourself for improper care; it could be
Botrytis blight. The fungus responsible, Botrytis cinerea, (Fig. 2) infects
the flowers before they are harvested, then develops inside the flower while in
transit in the cool, moist conditions which allow it to thrive. Don’t blame
your retailer for selling bad flowers either, she has no way of knowing which
roses might be infected because there are typically no symptoms until the
flowers begin to open more fully in the home. There’s nothing you can do to
avoid a couple of infected roses in that beautiful dozen you picked up at the
last minute; just enjoy them while they last and get rid of the droopy ones
quickly.
It’s a long time until Summer, but the same fungus causes
leaf and flower blight; and cane dieback on roses in the landscape. (Fig. 3). To
help reduce spread on your roses in the landscape be sure to remove spent
blooms and prune out canes showing signs of dieback. Remove the pruned material
from the garden promptly. Several fungicides are available for garden roses. Be
sure to follow label directions and safety cautions. Shrub type (e.g. Knockout)
roses typically have fewer problems with botrytis blight.