Understanding threats to Brassica crops: A case study
Identifying Black Rot.
Black rot (Xanthomonas campestris pv. Campestris) is a common disease among Brassica crops worldwide. It is prevalent within the wetter months of the year, normally around October in Northern Virginia. This is believed to occur as the bacteria is easily spread to multiple plants through the movement of water by farmers, animals, and other vectors. The disease can affect the economic value of a large portion of crops, including broccoli, radishes, kohlrabi, cauliflower, and kale.
The symptoms of black rot vary depending on the infected species and surrounding environmental conditions, but are largeley recognized by the presence of V-shaped lesions coming from the edges of the leaves on an infected plant. These lesions are normally yellow or brown and end when they reach a vein on the leaf. As a result of the lesions,veins on infected leaves become clogged and cause the death of portions of the individual plant.
This death is what gives the disease it's common name, as it produces a black polysaccharid referred to as Xanthan. This substance turns the veins of infected leaves black, and makes the death of each leaf more defined.