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


SummaryCavity spot caused principally by Pythium 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 registration status 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 build on a previous work in FV391a to develop artificial inoculation techniques for P. violae in order to produce cavity spot symptoms in pot and field grown carrots. The feasibility of large scale inoculum production using a large fermenter will also be evaluated.     

Project code:
FV 391B
01 August 2007 - 30 September 2018
AHDB Horticulture
AHDB sector cost:
Project leader:


FV 391b_GS_Final_2018 FV 391b_Report_Final_2018

About this project

Aim: To further develop artificial inoculation systems to induce cavity spot symptoms in pot and field grown carrots using P. violae. 
1. Test vital stains and different chemical treatments to assess P. violae oospore viability and increase germination.
2. Test the efficacy of different rates of P. violae liquid inoculum in producing cavity spot symptoms in pot grown carrots in the glasshouse
3. Test the efficacy of different rates of solid 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
Benefits to Industry: The main benefit to the industry will be to have access to a robust inoculation system for P. violae which results in consistent and reproducible levels of disease in pots and in the field. This will allow the efficacy of potential new control treatments such as fungicides, biological control agents, botanicals or other products to be efficiently and accurately evaluated. In addition, inoculation systems for P. violae will allow the study and understanding of early infection events including colonisation of carrot seedlings and subsequent development of cavities on maturing roots.