If you’re renewing an older planting Chalmers always recommends replanting over top-working. We are confident that the benefits of newly established vines, when prepared and established properly, will give the best results in terms of quality and only see a marginally longer lag time between productivity of the old and new planting.
It is important to understand that should you choose to top work the vines you have currently planted in your vineyard with a new variety, that this is not something we would recommend. There is always a risk of virus content in grapevines, and any viruses that are present in either the rootstock or the scion will move between the two. If these vines are top-worked with the new variety you are wanting, then this may add further to the virus load of the existing vine and can impact on the quality you can achieve in your vineyard. Even if the new bud used for top-working has a ‘virus free’ status it can still pickup any existing virus from the established vine in your vineyard.
If you decide to continue with your top-working program, then before we can supply cuttings of your desired variety, we require that you provide us with a virus status fro the vines in question. You can do this by sending a tissue sample(s) from your existing vines that you will be top-working for virus testing to confirm that there are no viruses that would prevent a compatible graft. This sample should be sent to a recognised Virus Testing Laboratory such as AWRI Virus Testing in SA or Agriculture Victoria Diagnostic Crop Health Services.