Black leg of brussel sprouts, broccoli, and cauliflower is caused by the fungus Phoma lingam. The disease occurs sporadically in the High Plains during extended periods of cool, moist weather. Infections often start at or below the soil surface when seeds are exposed to contaminated crop debris. The disease damages the water-conducting tissues, resulting in blackened streaks in stems. The pathogen survives between susceptible hosts in crop debris, contaminated seed, and soil.
Black leg can cause lesions on leaves and stems, above or below the soil. Infected stems have a characteristic semi-dry, blackened rot with small black fungal fruiting bodies (pycnidia) covering the infected area. Affected plants are often stunted and wilt. Blackened streaks are apparent when stems are cut in cross-section.
No biological control strategies have been developed for black leg.
Plant seed free from the black leg pathogen. Practice a three-year or longer rotation to non-hosts. Deeply incorporate crop residues after harvest to reduce pathogen survival.
Fungicides are most effective when used in combination with cultural control strategies. Fumigation provides effective control of black leg, but is rarely economical in the High Plains.
Product List for Black Leg:
Pesticide |
Product per Acre |
Application
Frequency
|
Remarks |
Iprodione—not all formulations available are listed |
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|
Rovral |
2 lb |
-- |
Direct sprays toward base of plants; Maximum of 2 applications per season; 0 day PHI |
|
Rovral 4F |
2 pts |
-- |
Direct sprays toward base of plants; Maximum of 2 applications per season; 0 day PHI |
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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, Co lorado, 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. |
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Categories: Cole Crops, Disease, Black Leg
Date: 04/01/2007