Carrots: The Epidemiology of Carrot yellow leaf virus (CYLV) - the development of a decision support system for the management of carrot viruses in the UK

 

Arising from previous carrot virus studies (Fox, 2013: FV382a), several key knowledge gaps in the understanding of carrot virus epidemiology were identified. Closing these gaps will allow the industry to better understand the effects of viral infection in carrot fields and in doing so move from a reactive to a proactive approach to virus management.

 

The fundamental principles of plant virus management are:

- Plant clean seed
- Grow in absence of vectors
- Grow in absence of virus reservoirs
- Isolate from similar crops
- Use resistant (or tolerant?) varieties
(*adapted from Brunt et al, 1996)

 

Although these points were formulated for virus management in seed potato crops (Brunt also included early haulm destruction), the key principles are transferable to any crop, and considering the relative importance and influence of these factors in a given cropping system could allow the development of decision support system for carrot growers in managing the impact of virus disease in carrots.

 

With the limited insecticidal chemistries currently available, the carrot industry is facing an increasing challenge managing the problems caused by virus infection. Of the viruses currently affecting carrot crops, Parsnip yellow fleck virus (PYFV) has been recognised as an early season threat, leading to seedling death, whilst the Carrot Motley Dwarf (CMD) complex has been linked to problems occurring later in the season. This means the limited aphid management options available to growers is already stretched in providing season long prophylactic treatment. With the recent association of the little studied Carrot yellow leaf virus (CYLV) as the causal agent of internal root necrosis, the industry faces a third major viral threat.

 

It is recognised that the work plan detailed here does not cover all aspects of work required to move to an effective decision support programme for the management of carrot viruses. Further project work is expected to follow from this project to investigate the role of variety, agronomy, reservoirs of virus and effective management strategies.

The long term aim is to close the necessary knowledge gaps to work towards providing effective decision support to growers for the management of viruses affecting carrot crops. The specific aim of this project is the first step towards that aim in confirming the role of UK aphid species in the transmission of CYLV and subsequently experimentally demonstrating the role of CYLV in the development of carrot root necrosis.

 

The aim will be achieved by plugging the knowledge gaps on carrot virus epidemiology. The main objectives will be to investigate:

a) Aphid transmission of the main UK carrot viruses
b) Influence of CYLV on development of symptom