Celery: Evaluation of alternative seed treatments for the control of Septoria apiicola (celery leaf spot)

Celery leaf spot (Septoria apiicola), also known as ‘late blight’, is the most destructive disease of field grown celery crops. Initially seen as small brown spots on leaves and stems, the disease can progress rapidly and render the whole crop unmarketable if left unchecked. Seed-borne inoculum is thought to be the major cause of outbreaks of celery late blight. Seed treatment remains an important component of disease management for celery Septoria.

Deliverables from this work were:

• A knowledge review on alternative treatments for the control of seed-borne diseases, particularly in relation to Septoria
• Information on the efficacy of a range of seed treatments for celery Septoria, enabling the industry to make an informed decision on viable alternatives for use in celery production.

Findings:

• Hot water treatment (48^oC, 30 min) without a pre-soak, is the best option available for treatment of organic celery seed to control Septoria apiicola (celery leaf spot) at present.
• Under specific conditions, celery seed treatments with hot water, Jet 5 (peroxyacetic acid) and Wakil XL (cymoxanil + metalaxyl-M + fludioxonil) gave significant reductions in the levels of Septoria apiicola in celery seed, without affecting seed vigour. However, the standard industry treatment (warm water thiram soak) was the only treatment tested that eliminated septoria.

See related AHDB Factsheet on the management of celery leaf spot

The aim of the project was to determine the efficacy of a range of seed treatments for celery Septoria that could provide alternatives to thiram, for both conventional and organic celery production. Seed treatments were assessed according to their effects on, i) incidence of seed-borne inoculum, ii) seed germination, iii) seedling infection, and iv) seed viability after storage.