Diseases of Sweet Clover

 
 
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 Brown Root Rot
Plenodomus meliloti

What to look for?
This disease can affect alfalfa and clover as well as sweet clover. This is a low temperature fungus that attacks the crowns and roots under deep snow cover. The sweet clover may sprout in the spring and then die-off due to a root and crown rot. Most crop losses are usually minor. The fungus survives over summer as picnidia or mycelium on the roots.

Damaged crown.
Photo: Evans		Picture description
Damaged crown.		 Damaged crowns.
Photo: Davidson		Picture description
Damaged crowns.
.
Management strategy
No control procedures.

Downy Mildew
Peronospora trifoliorum

What to look for?
Downy mildew shows up on clover in wet spring's; it can also affect alfalfa and sweet clover. Most damage is caused by leaf drop from the first cut. Losses are generally minor.

Infected leaves are light green with grey fungal mycelium on the under surface. The fungus infection may be systemic and it can infect the crowns.

Mildew infected leaves.
Photo: Ellis		Picture description
Mildew infected leaves.
.
Management strategy
Cut crop early to avoid excessive leaf drop.

Witches' Broom
Mycoplasma or Phytoplasma

What to look for?
Witches broom and clover phyllody are virus-like diseases that are spread by leafhoppers. These diseases may be brought in from the United States by migrating leafhoppers in May or June.

Sometimes plants infected late in the season will overwinter and serve as a source for feeding leafhoppers. Infection levels are generally less than 10% and white sweet clover is usually the most affected.

Seed potatoes growing in areas of high incidence of these diseases may have levels of 5-10% in the potato seed. Infected potato seed will not produce potatoes the following year. These diseases will not spread from infected potato to healthy potato.

Typical multiple shoots.
Photo: Evans		Picture description
Typical multiple shoots.
.
Management strategy
No control procedures but do not grow seed potatoes adjacent to a perennial legume crop.

Photographs and information assembled and prepared for ARD by Dr. Ieaun R. Evans Agri-Trend Agrology Ltd.		  
 
 
 
For more information about the content of this document, contact Ron Howard.
This document is maintained by Shelley Barkley.
This information published to the web on December 16, 2003.
Last Reviewed/Revised on January 4, 2011.