Black rot is caused by the bacterium Xanthomonas campestris pv. campestris, and can be very damaging to cabbage and cauliflower under rainy, warm conditions. The disease begins when bacteria are splashed onto leaves by rain or irrigation water, multiply to form large populations, and infect the plant through natural openings or wounds. The bacteria progress down the water-conducting system, systemically infecting the entire plant. Bacteria are easily disseminated by irrigation water and splashing rain. The pathogen can survive between susceptible hosts as an epiphyte on weeds, in infected crop debris, and in or on contaminated seed.
Black rot symptoms initially appear as yellow to light brown patches at leaf margins; veins later darken in infected leaves. Infected leaves later turn brown and dry out, leaving angular-shaped lesions on the leaf margin. Extensive necrosis develops as the bacteria spread within the leaf blade. Vascular tissues become brown as bacteria move throughout the plant. In severe cases, the disease can induce an off flavor to develop in the cauliflower curd that can cause it be rejected in the market. Plants infected in the seedling stage are stunted and may die.
No biological control strategies have been developed for black rot.
Plant high quality seed and transplants free from the black rot bacterium. Hot water treatments can reduce seed contamination, but may reduce seed germination. Practice at least a three-year rotation between susceptible crops. Eliminate weeds in and around fields that can be a reservoir for the black rot pathogen. Deeply bury crop residues to speed decomposition. Avoid sprinkler irrigation where possible. Varieties less susceptible or resistant to black rot should be planted where available.
Copper-based bactericides provide some suppression of black rot, but may leave unsightly residues on heads. Bactericides are most effective when used in combination with cultural control strategies.
Product List for Black Rot:
Pesticide |
Product per Acre |
Application
Frequency
|
Remarks |
Copper and Copper Mixtures |
|||
|
Basicop |
3-4 lb |
7-14 days |
Crop injury can occur |
|
Champ Dry Prill |
0.33-0.66 lb |
7 days |
Crop injury can occur |
|
Champ Formula 2 |
1.33 pt |
5-7 days |
Crop injury can occur |
|
Copper-Count-N |
1-3 qt |
7-10 days |
Crop injury can occur |
|
Cuprofix Disperss |
1.5-2.5 lb |
5-10 days |
Crop injury can occur |
|
Kocide 101 |
1-2 lbs |
7-10 days |
Crop injury can occur |
|
Kocide DF |
1-2 lbs |
7-10 days |
Crop injury can occur |
|
Kocide 4.5LF |
0.66 -1.33 pts |
7-10 days |
Crop injury can occur |
|
Kocide 3000 |
0.5-0.75 lb |
7-10 days |
Reddening of older leaves may occur on broccoli, and a flecking of wrapper leaves on cabbage |
|
Ridomil Gold/Copper |
1 pack/per 2.5 acres |
14 days |
Make 2 to 4 total sprays; 7 day PHI |
|
Top Cop + S |
4 pt |
7-10 days |
Crop injury can occur |
|
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. |
|||
Categories: Cole Crops, Disease, Black Rot
Date: 04/01/2007