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.


​Click image to enlarge


Fig. 1. Rose with botrytis blight 


Fig. 2. Botrytis producing spores on infected rose petals 


Fig. 3.  Rose cane canker and dieback caused by Botrytis cinerea.