Happy Easter! I’m getting this in early – by the time I do the next Observations Easter will have been and gone.
Pruning – by and large the weather has been pretty good for the last couple of weeks so it’s a pity that the pruning match was cancelled because of lack of entrants – maybe just as well because the land at Burnt House might have been quite sticky after the winter’s soaking.
How many of you pay attention to pruning wound protection to reduce Grapevine Trunk Disease (GTD)? – I was recently talking to a well-known purveyor of vines who was very dismissive of the threat from GTD. I am not alone in thinking that this will be an increasingly important threat to vine health as climate change increases the amount of water in the atmosphere (every +1c accounts for 7% rise). A recent newsletter from Forest Research (part of Defra) highlighted the increasing threat from phytophthora and other diseases in woody plants as the climate warms – we are already seeing this with the rise in downy mildew outbreaks. Even in the short time that I have had anything to do with grapes (11 years) downy mildew has become rife – 50 years ago it was rarely a problem!
It will be interesting in years to come to see if those who protect pruning wounds with BlocCade or Vintec have any difference in trunk disease levels to those who don’t. One of my clients has inherited some 40-year-old Bacchus (on Geneva double curtain, soft pruned!) and there are so few that are still healthy that the whole lot needs replacing.
This is a vine that looked perfectly healthy one week but succumbed to trunk disease the next week. Below are sections of vines also affected by trunk disease
The mottling is most likely to be Botryosphaeria (on left), with Petri disease (middle pic) and Eutypa Dieback on the right –I am not going into GTD at the moment – there are entire libraries devoted to the subject – below is a link to a 15-year review on the subject:
https://apsjournals.apsnet.org/doi/epdf/10.1094/PDIS-08-17-1181-FE
Will Robinson had a good article in the last Fruit and Vine magazine and recommended soil and tissue analysis – you may know what is in your soil but that won’t tell you what the vines are taking up, hence the need to do both. Jonathon Telfer, head of Lancrop labs advises petiole testing for nitrogen and leaf testing for trace elements and to take petiole/leaf samples at the same time of day for subsequent sampling because the composition of the sap changes through the day. Testing for tissue nitrogen levels will allow you to correct any deficiency before picking – if you don’t need to use much yeast nutrient then your fertilizer applications (if any) are about right.
Something else that will exacerbate nitrogen and iron deficiency is sulphur deficiency – sulphur is a component of proteins, enzymes, chlorophyll and vines remove 4-8 kg/ha/pa; we don’t receive free sulphur from the atmosphere anymore so supplements needed either by soil (e.g. Epsom salts or fertilizer with added SO3), or foliar applications e.g. Kumulus, Microthiol, Thiotrac etc. I have found that applying Ferleaf 100 (iron) and Thiotrac 300 (sulphur and nitrogen) together works very well – they produce very good results (nice shiny green leaves)
When taking leaf samples (at full flower or veraison) remember to take the youngest fully expanded leaves – many of you will know this but it’s worth saying anyway! – and do this before any foliar feeds go on.
To mulch prunings or not? – if you have grass cover in the alleyways then yes, but if the alleyways are bare then no – remove the prunings and burn them asap. Research by the Geisenheim Institute et al has shown that mulching into grass greatly reduces the spread of overwintering fungal spores but mulching on bare ground allows these to be splashed up the trunk by heavy rain. In my own experience I have seen no increase in disease between either of these two practices – fungal spores are everywhere and will be blown in by the wind from other sources of infection many miles away. I think it is far more important prune thoroughly and remove any mummified berries etc then a robust spray of copper and sulphur near bud break followed with the spray program of choice.
Crown Gall in new plantings – in my last Observations I reported two separate incidences of crown gall in freshly planted Pinot Noir and Chardonnay (May 25) that had been planted by two well-known firms. I contacted them – one has done the decent thing and agreed to replace the affected vines (I think that the risk of infecting the replacements is low so long as all the diseased roots are removed), while the other supplier tried to fob me off by telling me that the galls were caused by the wind rubbing the new shoots against the tutor! I have seen many vines with wind rub where vines not tied to the tutor have chafed against the top of the Tubex, but not at the bottom!
So, if you have any new vines I urge you inspect them closely – the graft union should have a smooth callus, not some monstrous carbuncle that you see here.
Prices of sprays have jumped (what hasn’t?) so make sure your sprayers are in top condition – they will need a NSTS certificate “For all new PAE (Pesticide Application Equipment), the first test is due before the machine is 5 years old. Boom sprayers over 3 metres, air blast sprayers, and train and aircraft sprayers must be tested at least every 3 years.”
It is good practice to have the sprayer serviced every year-the money spent on servicing will repay itself by ensuring that those horrendously expensive chemicals go onto the vines accurately and efficiently – a breakdown just as downy mildew is ramping up doesn’t bear thinking about!
Frost – who has used or is thinking of using Antifrost? (article also in Fruit and Vine) – it almost seems to be too good to be true! The only downside that I can see is the need to apply every 7-10 days so if the ground is still a bit on the damp side there may be some good ruts appearing…
However, because it is not an authorised product then anyone with a drone and accompanying ID and licence (from the CAA) can apply it without an Aerial Spraying Permit (as far as I am aware! – check first!)
One of my clients wants to try Antifrost – I’ll let you know how it goes. If you are using frost fans etc don’t remove them until the end of May at the earliest.
My daughter gave me a book by Charles Walter Berry (as in Berry Bros& Rudd) for my birthday- a quote from it:
Good wine makes good blood,
Good blood causeth good humours,
Good humours causeth good thoughts,
Good thoughts bring forth good works,
Good works carry us to heaven,
Ergo,
Good wine carrieth us to heaven.
That’s all – I have vines to prune, wires to drop, tighten, repair etc
Graeme