Crown Rot

Crown rot may sound like a great punk rock band, but it can destroy nearly every plant in your garden.

Swiss chard infected with southern blight (Scot Nelson) Public Domain

Crown rot, also known as southern blight and southern stem blight, is more of a symptom than a condition. Several different diseases can cause crown rot. And some people call it southern stem rot, and others call it white mold, not to be confused with the Sclerotinia white mold growing on your grocery store strawberries. 


Crown rot can be a sign of infection by several fungi or oomycetes (think amoeba with attitude) common in the soil. It favors heavy clay and wet conditions from over-watering and flooding. Once crown rot occurs, it is nearly guaranteed to kill a plant.


Crown rot symptoms

Signs of crown rot include rotted plant tissue at ground level, wilting, leaf drop, trunk discoloration, and leaves that turn yellow or even red or purple. Established trees may ooze a dark sap around the infected area. Older plants may survive a few years, but young plants die quickly.
 
If crown rot occurs in the garden, your best choice is to pull up the plant and discard it. In rare cases, you may be able to salvage an infected tree by pulling the soil away from the trunk and cutting away diseased areas. Fungicides are ineffective in treating crown rot.


Preventing crown rot

Prevention is the best course of action in areas prone to crown rot. To reduce the likelihood of crown rot taking hold, use these preventative measures:

• Ensure proper drainage. 
• Amend soil with organic matter and compost.
• Plant trees properly, with grafting unions above ground level.
• Keep the mulch at least 6” away from trunks.
• Never allow sprinklers to spray tree trunks.
• Rotate crops each year.