Parsley root and crown rot

Parsley root and crown rot is cause by the soil-borne fungus Phytophthora primulae, which chiefly infects parsley plants. It is usually associated with poor drainage, especially in overwintered crops.

Symptoms
The first indication in a field may be patches of stunted plants with yellowing foliage. The roots of infected plants will show a brown discolouration when cut open. The discolouration will become darker as the infection progresses until the outer layer of the root begins to fall away. A severe infection will result in complete foliage collapse and plant death.

Control
Diseased plants and associated growing media should be removed and discarded into a covered skip. Regularly clean and disinfect benches, matting, tools and propagation areas if root and crown rot is a known problem. Disinfectants with activity against Phytophthora species include Jet 5 and sodium hypochlorite.

Chemical control
The disease can be managed with a fungicide based on metalaxyl-M.

Cultural control
Since the spread Phytophthora spores is facilitated in soils with poor drainage, crops should be grown on small ridges to avoid waterlogging in areas where crown and root rot is known to be a problem. Increasing the period of crop rotation can reduce levels of inoculum in the soil, but the fungus has been found to survive after 5 years.