Black rot is considered the most important disease of crucifers across the world and can attack its host at any stage of growth. Cauliflower and cabbage are the most readily affected crucifer hosts and suffer significant yield loss as a result of the disease. On cabbage, black rot causes yellow to brown V-shaped lesions to develop on the edges of leaves and move inwards towards the midrib. As the disease progresses, the lesions turn darker, and leaves may wilt and fall from the plant. In the advanced stages of the disease, veins in the affected area will darken.
The disease is causes by a bacteria, Xanthomonas campestris pv. campestris, which can be spread via wild hosts, water or, most commonly, infected seed. Even symptomsless plants may produce infected seed so it is important to try to source certified disease-free seed before planting. For more information about how to control this disease, read September’s Factsheet of the Month, Control of Black Rot in Cabbage, which has been written by staff from the Ministry of Agriculture in Grenada.
Vegetable farmers in the Kayunga and Mukono districts of Uganda are reporting crop losses due to black rot disease. One farmer, Twaha Kahooza of Kyampisi village, Kayunga Sub-county, says he had planted four acres of cabbages and was expecting about Shs18m (about £4,500 or US$7,000) from the harvest, however he only managed to get Shs5m (about £1,200 or US$2,000).
Black rot is caused by the bacterium Xanthomonas campestris pv. campestris and is one of the most destructive diseases of cabbage and other crucifers such as broccoli, brussels sprouts, Chinese cabbage, collards, kohlrabi and mustard. The disease is usually most prevalent in low lying areas where plants remain wet for long periods. The disease is characterized by a yellow V-shaped lesion at the leaf margin which turns brown as the leaf area expands. The disease can also affect seedlings and can enter the plant through insect feeding or injury to the plant. Management of black rot in crucifers includes obtaining certified, pathogen free seed, ensuring there is enough space between plants and crop rotation.To read more about black rot and black rot management visit factsheets on the Plantwise Knowledge Bank.
To read a Plantwise Factsheet for Farmers written in Uganda click here.
To find out more about Plantwise plant clinics running in Uganda, click here