HPIPM:Aphanomyces Root Rot Sugarbeets

Author: Howard F. Schwartz, David H. Gent, Robert Harveson, Barry Jacobsen, and Martha Mikkelson

Identification and Life Cycle

Aphanomyces root rot is caused by the fungus-like pathogen Aphanomyces cochlioides. Seedling infection occurs optimally when soil temperatures are less than 60ºC. The pathogen survives between sugarbeet crops as dormant resting structures (oospores) in soil and pathogenically on weeds.

Plant Response and Damage

Aphanomyces root rot rarely causes pre-emergence damping off, but soon after emergence the pathogen invades the cortex of the hypocotyl, causing a brown discoloration, which can advance up to the base of the cotyledon. Seedlings may become flaccid, fall over, and die, but often recover. Plants are dwarfed and seldom produce normal mature plants. Yield losses can be significant.

Biological Control

No biological control strategies have been developed for Aphanomyces root rot.

Cultural Control

Plant high quality seed into warm, well prepared seedbeds that encourage rapid germination. Avoid excess irrigation and poor drainage. Rotation with dryland crops before sugarbeets may reduce damage. Some varieties are less susceptible or resistant to Aphanomyces root rot, but most are susceptible to the disease.

Chemical Control

Treat seed with a broad-spectrum fungicide such as hymexazol (tachigaren). In furrow phosphorous fertilization combined with seed treatment may improve disease control.

The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality.