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

Summary: Cavity spot caused principally by P. violae is the major disease of carrots in the UK. Management of the disease relies on the fungicide metalaxyl-M although its efficacy is variable. The reliance on this single fungicide is of major concern to the industry as its future efficacy and sustainability is uncertain. To address this, previous AHDB Horticulture projects have evaluated potential new control measures including fungicides, biological control treatments, calcium applications and biofumigation. However, progress has been severely hampered by a lack of sufficient disease levels in many of these trials and hence new treatments have not been clearly identified. This project will test different growth media and conditions for P. violae inoculum production and define appropriate rates required for symptom development in pot and field grown carrots. The feasibility of large scale production of inoculum using solid state fermentation will also be evaluated.

Aims and Objective: 

(i) Project aim: 

To develop artificial inoculation systems to induce cavity spot symptoms in pot and field grown carrots using P. violae. 

(ii) Project objectives: 

1. Develop growth media and determine conditions to optimise inoculum production of P. violae mycelium / oospores by different isolates in controlled environment 

2. Test the efficacy of different rates of P. violae inoculum in producing cavity spot symptoms in pot grown carrots in the glasshouse

3. Test the efficacy of different rates P. violae inoculum in producing cavity spot symptoms in field grown carrots

4. Examine the feasibility of large scale P. violae inoculum production in solid state fermentation