Science Into Practice - Treating cavity spot on carrots

FV 391a Carrots: Development of artificial inoculation techniques for cavity spot caused by Pythium violae

Cavity spot produces watery sunken pits on the surface of carrots that frequently result in crop rejection. Caused principally by Pythium violae, it is the major UK carrot disease. Management relies on fungicide metalaxyl-M, although its efficacy is variable and relying on a single product can cause resistance to develop. Reliance on this single fungicide is of major concern to the industry because its future efficacy and sustainability is uncertain.

Previous AHDB Horticulture projects evaluated a range of potential new controls including fungicides, biological treatments, calcium applications and biofumigation. However, such is the nature of research that you do not necessarily get reliable disease pressure when you need it to test out new products. In this case, progress has been severely hampered by a lack of sufficient disease levels in field trials. As a result, new treatments have not been clearly identified.

Project FV 391a is testing different growth media and conditions for P. violae inoculum production, finding the appropriate rates required for cavity spot symptom development in potand field-grown carrots. The feasibility of large-scale production of inoculum using solid-state fermentation will also be evaluated.

Towards the end of year one, the project is progressing well. Growing some organisms in the laboratory can take days or even weeks, but growing Pythium in flasks to use for artificial inoculation takes more than six months. The first greenhouse pot trial has tested different inoculum concentrations, and seedling emergence, and damping off is being monitored. Cavity spot symptoms will be assessed on mature roots later in the year.

AHDB Horticulture

For details on all AHDB Horticulture activity, see horticulture.ahdb.org.uk.


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