VG97103 Celery Mosaic Virus

This 1997-2000 project investigated the outbreak of Celery mosaic virus (CeMV) in celery and other related crops in Australia.

The main purpose was to gain a better understanding of what viruses were infecting our Apiaceous crops, what their host ranges were and how widespread the virus was.

Specifically this project determined the effects of virus on celery and carrots, and assessed alternative management strategies.

This study revealed that CeMV was indeed prevalent in all celery growing districts in Australia. It had severe affects on celery quality and production.

As part of a total management system for CeMV in celery, petroleum oil sprays and plastic reflective mulches were trialed.

Findings :

Two new potyviruses closely related to Celery mosaic virus (CeMV) have been found in the Apiaceae growing in Australia:

1. Apium virus Y (APY)

2. Carrot virus Y (CVY).

Although closely related to CeMV, they do not appear to readily move between plant species in the field.

CVY and CeMV are prevalent in Australia’s major carrot and celery growing areas respectively.

The spread of CeMV in celery is linked to aphid pressure. High levels of CeMV in the field correspond with high aphid numbers in Spring and Autumn.

In carrots, virus can reduce yield (measured as weight), carrot length and carrot collar width, but it is dependent on variety.

However, virus had no effect on storage quality.

The five varieties assessed were: Senior, Leonore, Nantes, Steffano and Red Brigade.

Two alternative control strategies to help reduce the impact of CeMV were tested:

1. petroleum spray oils

2. coloured reflective mulches.

Both showed great promise.

The petroleum spray oil used in the trial delayed CeMV infection in the field and reduced CeMV infection overall.

Plastic reflective mulches were also effective in deterring aphids for landing in celery crops. Silver mulch was more effective than white which in turn was better than bare soil (Part 5).

Recommendations :

It is possible to manage the spread of Celery Mosaic Virus

1. Plant healthy celery seedlings in the field.

Seedlings sourced from outside the celery growing areas are less likely to be infected with CeMV.

In addition, future options for growers would be to test seedlings before they are transplanted out into the field, but this may be cost prohibitive.

2. Plant tolerant varieties.

At present, no resistant varieties are known, however further research is currently being undertaken by staff at IHD, Knoxfield to address this.

In the near future it is hoped that growers will be able to plant virus-resistant crops to combat both CeMV and CVY.

3. Plant new crops far away from mature crops.

This is a relatively simple and effective control method that can be implemented immediately by growers.

Growers need to be encouraged to allocate some time to reorganising their planting regimes to cater for this.

4. Plant celery seed beds far away from celery crops.

The longer the plants are in the ground the more likely the plants are to acquire virus.

Because aphids are more likely to feed on older more challenged plants they are more likely to acquire the virus from the celery seed beds and pass on the virus to other plants.

5. Control wild fennel and feral carrot on the farm.

The importance of controlling weeds which act as virus reservoirs as well as alternative food sources for the aphids is paramount in helping control the transmission of virus from weeds to crops.

This is a cultural control method that can be immediately implemented by the growers.

6. Plough in old crops and crop debris as soon as possible.

This too is another recommendation that can be immediately implemented by growers.

The sooner the plants are ploughed the less likely aphids will be to acquire the virus from the old crop and pass it on to the new crop.

7. Take a break in production

Studies from the US recommend at least 2-3 months.

The break in production will help break the cyclic effect of virus from one crop to another. This type of cultural control has proved to be very successful in South Australia and the US.

Although there seems to be no evidence available world-wide with regard to the seed transmissibiUty of CeMV this question has not been thoroughly addressed.

If CeMV and CVY are seed transmitted, implementing a certified seed program, together with all the cultural control
recommendations above will help control the viruses in the Apiaceae.

Acknowledgements :

The assistance of the steering committee members, who provided constructive comments and information, is gratefully acknowledged. Members of the group were the Victorian Celery Growers Association, in particular Tom Schreurs, and Silvio Favero.

A large number of inpiduals provided support throughout the duration of the project allowing us to use field sites and gathering of important information.

We thank the following people:

• Evita Alberts	• Tim Burrell	• Sandy Cochrane
• Gazzolla Farms	• Adrian Gibbs	• Leo Kelly
• Tony Kourmouzis	• Rocco Lamattina	• Russell Lamattina
• Lindrea Latham	• Anne McKenzie	• Thomas Persley
• Alexie Rowles	• Brad Rundle	• Len Tesererioro
• Victorian Celery Growers Association		• Calum Wilson

This project was commissioned by Horticulture Australia Limited and funded by the Vegetable R&D levy and the Victorian State Government..

The Australian Government provides matched funding for all HAL’s R&D activities.