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Guidelines: Control of leafroll and fanleaf in nurseries
Nico van Rensburg (VIA)
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PART 3: Nursery units
1. Introduction
- Because of the sporadic appearance in vineyards throughout the entire wine industry of virus symptoms, particularly of leafroll, and the spread of fanleaf in the lower Breede River Valley, the Vine Improvement Association (VIA) has updated its precautionary and control measures so as to more effectively combat the spread of leafroll and fanleaf within planting units as defined in terms of the SA Plant Certification Scheme for Wine Grapes.
2. Precautionary and control measures
- Nursery units are established with grafted vines derived from scion and rootstock plant material originating from mother units, in order to provide nursery vines to producers for the establishment of commercial vineyards.
2.1. Isolation
- An isolation distance of three metres from other vineyards must be maintained.
- An isolation distance of one metre from other nursery vines must be maintained.
2.2. Soil requirements
- Virgin soil or soil which tests free of the fanleaf virus vector.
- Drainage and run-off water from other vineyards must not be permitted to flow to a nursery unit.
- Should this land previously have been used for a vineyard or nursery, as many as possible of the remaining roots must be removed.
- In the case of old vineyard or nursery soils, the land must be permitted to rest for at least a year.
2.3. Inspection of units
- Inspections must take place three times a year - in summer, autumn and winter.
2.4. Care
- Plants within a nursery unit must be cared for in a manner conducive to obtaining plant material of a high quality.
2.5. Weed control
- Plants within a nursery unit must not be overgrown with weeds.
- Weeds must be controlled by following a specific weed control programme.
2.6. Absence of mealybug infestations
- No mealybug or visual signs thereof may be present on the plants or plant material.
2.7. Removal of vines
- Vines showing visual symptoms of leafroll must be removed continually.
- Nurserymen must record all removals and submit a written report to the Plant Improvement Organisation and the Vine Improvement Association.
- Deviating vines
- Must be removed on a continuous basis
- In instances where a large number of deviating vines occur adjacent to one another, these should be clearly demarcated.
2.8. Monitoring for mealybug
- Monitor the appearance of mealybug continuously during normal nursery activities.
2.9. Control of mealybug
- As soon as a mealybug infestation is detected, the entire nursery unit must be sprayed with a registered mealybug insecticide, applied in accordance with the prescribed concentrations.
- Use hand-held spray lances and not mist blowers.
2.10. Control of ants
- As soon as ant infestation is detected, the areas where they occur must be sprayed with registered ant insecticides, from December onwards, in accordance with the prescribed concentrations and using hand-held spray lances.
2.11. Movement of people and implements
- Should it be necessary to move people or implements to a certified nursery unit from an uncertified nursery unit, the following precautions are essential:
- Clean spray all tractors and implements;
- Disinfect all pruning shears and
- Clean protective clothing.
3. CONCLUSION
Research workers are presently engaged in a number of Winetech-projects covering various disciplines and aimed at the combating and control of the spread of leafroll. Although these precautionary measures may be further augmented in the future, as and when research results are made available, the indications are that the present measures can contribute positively towards the combating of leafroll and fanleaf in commercial vineyards throughout the entire wine industry.
Compiled from the following:
Addison, P., Protocol for ant control, Winetech, June 2003.
Carstens, R., Leafroll review, Winetech, December 2001.
Government Printer, South African plant certification scheme for wine grapes, Government Gazette, 28th August 1992, as amended.
Walton, V.M., Protocol for the combating of mealybug infestations in a vineyard unit, Winetech, December 2001.
Walton, V.M., Pringle, K.L. and Daane, K.M., Protocol for pheromone traps and monitoring of mealybug in South African vineyards, Winetech, June 2003.
For more information, contact Nico van Rensburg at the VIA, at tel. (021) 872 1831, fax (021) 872 0335 or e-mail plantpro@iafrica.com
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