Diseases and Pests
The disease is usually more severe on cold, wet, acidic soils and is spread by drainage water, infested soil on equipment, tools, or shoes, and infected transplants. Resting spores remain viable in the soil for up to eighteen years and the repeated production of brassica crops can lead to a rapid build-up of the pathogen. The disease is favored by soils with a pH less than 7.0.
- Maintain a high pH by regular applications of lime. Calcitic lime is preferred over dolomitic, except where magnesium levels are low.
- Maintain high levels of calcium and magnesium. High pH can lead to boron deficiency in coarse soils. Apply boron as needed as a foliar spray or in the transplanting water.
- Finely ground lime alters the pH more quickly than coarse granules.
- Long (5-7 years) rotations between brassica crops.
- Improve soil drainage.
- Control brassica weeds.
- Avoid the movement of infested soil into clean areas.
- Produce transplants in clean soil or soilless media.
- Do not use irrigation water that has been contaminated with resting spores by run-off from infested fields into irrigation