Phoma, or stem canker, is a fungal disease (Latin name Leptosphaeria maculans ) which can cause significant crop losses in winter broccoli and other brassicas in epidemic years.

Initial infections are caused by fungal spores which infect the young leaves of the recently emerged crop to form phoma leaf lesions.

If this happens early in the season when the plants (and leaves) are small, the pathogen grows down the leaf stalk to infect the stem. Later in the season, the infected stem develops into a large “canker”, preventing water uptake of the plant. In severe cases, an infected plant may die.

Most broccoli plants survive and produce spears. Additional nitrogen has helped.

Severity of phoma stem canker epidemics is affected by:

• the number of spores in the area & severity of the epidemic
• variety
• cultivar resistance
• climate - wet, warm weather
• garden practices - clearing crop debri, crop rotations etc

Fungicide spray treatments for phoma/stem canker are not justified in the vegetable garden