HPIPM:Rhizoctonia solani (belly rot)
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Author: Howard F. Schwartz and David H. Gent
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Identification and Life Cycle
Belly rot is caused by the soilborne fungus Rhizoctonia solani, and can be a serious problem on cucumbers grown for pickling. The disease is most damaging to cucumber, but the pathogen can attack all cucurbits to some degree. R. solani is a very common soil inhabitant and invades cucumbers in contact with soil. The disease can occur over a range of temperatures (46 to 95ºF), but is most damaging near 80ºF. Temperature is more important than moisture for disease development, but high humidity and excessive moisture favor infection. The belly rot pathogen can be disseminated within and among fields by moving soil and infected plant parts by equipment and irrigation water. R. solani survives in the soil as dormant mycelium and in infested crop debris as dormant sclerotia. It is also a pathogen of many weeds and other crops, but only certain strains of the fungus (AG-4) can attack cucumber.
Plant Response and Damage
Belly rot symptoms occur on the underside and blossom end of cucumber fruit, producing water-soaked, tan to brown lesions. As the disease progresses lesions become sunken, cratered, irregular in shape, and dried. Infected fruits are firm and a soft rot seldom occurs. Belly rot reduces the quality and marketable yield of cucumbers.
Management Approaches
Biological Control
No biological control practices have been developed for belly rot.
Cultural Control
Practice a three-year or longer crop rotation between cucurbit crops. The belly rot pathogen can attack many weeds; thorough weed control is essential for crop rotation to be most effective. Crop debris should be promptly and thoroughly incorporated after harvest to hasten the breakdown of the pathogen’s dormant resting structures. Belly rot can be controlled effectively by not letting fruit touch the soil. Plastic mulches are often effective in preventing belly rot in semi-arid and arid production regions.
Chemical Control
Soil-applied fungicides provide inconsistent disease control. Soil fumigation can be effective but is generally not economical in the High Plains.
Product List for Belly Rot:
| Pesticide | Product per acre | Application Frequency (days) | Remarks |
|---|---|---|---|
| Azoxystrobin | |||
| Quadris | 11.0-15.4 fl oz | 5-14 days | Maximum of 4 applications or 2.88 quarts per season; Alternate Quadris with fungicides with different modes of action; 1 day PHI |
| Chlorothalonil | |||
| Bravo 720, Ensign | 1.5-2 pt | 7 days | Do not graze or feed debris to livestock; 7 day PHI |
| Bravo Ultrex | 1.4-1.8 lb | 7-10 days | Maximum of 16.5 pounds per season; 0 day PHI |
| Bravo WeatherStik | 1.5-2.0 pt | 7-10 days | Maximum of 20 pints per season; 0 day PHI |
| Echo 720 | 1.5-2.0 pt | 7-10 days | Maximum of 2.5 gallons per season; 7 day PHI |
| Echo 90DF | 1.2-1.6 lb | 7-10 days | Maximum of 16.67 pounds per season; 7 day PHI |
| Echo Zn | 2.2 to 2.8 pt | 7-10 days | Maximum of 3.6 gallons per season; 7 day PHI |
| Thiophanate Methyl | |||
| Topsin M 70WP | 0.5 lb | 7-14 days | Maximum of 3 lb per season; Alternate fungicide sprays or tank-mix with fungicides with a different mode of action; 1 day PHI |
| Topsin 4.5 FL | 10 fl oz | 7 days | Maximum of 60 fl oz per season; Alternate fungicide sprays or tank-mix with fungicides with a different mode of action; 1 day PHI |
| Topsin WSB | 0.5 lb | 7-14 days | Maximum of 3 lb per season; Alternate fungicide sprays or tank-mix with fungicides with a different mode of action; 1 day PHI |
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.
