KYM LUDVIGSEN – Viticultural Consultant
POINTS TO PONDER ~ 1/11/13
1. Pests and Diseases
In the last few weeks a number of growers in a wide range of Wine regions have experienced frost damage. There have been a number of articles read and opinions given about what to do after a frost.
The most sensible advice I heard was to take a week off – but if it’s your income for the year there needs to be some answers to the questions you have about the impact of the frost on your vines.
In the June 2013 edition of the Grapegrower & Winemaker there was a 1 page article that was pretty good and I was sent an article from the Barossa Grape & Wine Association (2013/14 V1#3) which supports the view to do nothing.
Both suggest maintaining the fungicide programme as you will get some fruit from the secondary and tertiary buds but ripening maybe uneven.
In dry times an irrigation could be useful and in all areas maintain your nutrition programme – even a bit more nitrogen to get the vines back.
A bad frost may see your pruning costs rise in winter 2014 – more buds break after an injury.
Some people advocate shoot removal from frosted vines. This is likely to get an evener ripening at harvest. Some suggest using herbicides other urea to bare the vine back to the cordon. Really not needed – either to cut shoots off or to spray them – as it changes little.
I spend a few hours at least once a week strolling thro my vineyard recording phenology and what I see in the vines. Apart from it being a good thing to do – vines are pretty good company – it helps to work out what to do for the upcoming week.
At this time of year the vines are actively growing – a bit of hot weather and a little water gets them moving rapidly – so regular fungicide applications at 10 to 15 day intervals are good especially if you are using broad spectrum fungicides like wettable sulphur and copper products to keep the new shoot growth protected.
At flowering I like to think that I can protect the flowers – so if I was to use a more strategic approach to fungicide use this is the time I would concentrate the high value, disease specific fungicide applications.
My boss in the 70’s used to say chemicals applied when the vines were flowering was a bad thing so he used to get us to apply fungicides when he saw his first flower and then again when he judged the vines 80% thro flowering followed by another fungicide 2 weeks later – he reckoned that was what worked for him as he never got disease infections. He also liked blue skies over flowering and warm weather – reckoned that meant a good crop.
Experience is a great teacher provided you listen to the lesson and see what you are learning!
So using the low impact protectant fungicide programme follow the week 2,4,6,10 application programme (I’d slip in a week 8 spray as well) keep the sulphurs going and consider what you will do around flowering.
Rots maybe an issue this year as in vineyards where I have been I have seen a little leaf botrytis and think a broad spectrum bunch rot application over flowering and 2 weeks later a good investment.
The best thing you can do to manage diseases in your vineyard is to understand what gets them going, what climatic conditions, what pests help them and what their life cycle is. Read about powdery, downy, LBAM and bunch rot especially.
LBAM are found flying around the place at the moment – look especially in the shoot tips. Find an egg mass and watch them mature to help plan your spray programme.
At 80% flowering petiole samples are taken. A number of people will arrange these for you – at present I’m planning to use APAL Laboratory (www.apal.com.au) 0883320199 – who maintain they have some pretty competitive pricing and all the permits need for us Victorians to ship petioles to their labs. Others provide the same service – Ben Thomas Consulting (www.benthomasconsulting.com.au )
Whilst the cockies have not arrived in any numbers – yet – I expect as the farmers start harvest we will get the well fed, resting birds biting shoots and dropping bunches to pass there time between their grain meals. Vandals is a fair description of their activities.
At this time of year it is great to see the Kangaroos lounging amongst the vines. They are a pretty animal and I love the way they move around. We do live in a wonderful place.
I was chasing Lucky down the road today – nimble bugger really – he can really move along for an old man and so adept at 90º turns – makes the 4 wheel motor bike a tad useless and there I was wishing for a couple of dogs as he bolted off into the vines. I was reminded of the coyote and the road runner….
2. Foliage Management
The warm and wet conditions have really got the vines moving along. I reckon they grew 100 cm over the weekend so the first wire lift must be close – usually done just before flowering.
The suckers on the vine trunks are also powering along and require removal. This process can be pretty slow when done by hand as each vine trunk has its shoots removed. Mechanical shoot knocking or chemical shoot removal are preferred methods to remove shoots on the vine trunks – quick and easy. These shoots are removed before they harden off and before they reach 100 cm (I’m thinking that’s about 6 inches in the old measures)
I’ve been looking at my Viognier thinking that I will be shoot thinning them pretty soon and maybe even take off a few bunches to lighten their load. These are going to travel a little harder this year – less loving care – and maybe they will be easier to handle.
Every day I think –I’m going to get to those replants and train them up and remove their grow guards but I also think maybe tomorrow …..
I’ve been looking at how well (or poorly) buds have burst both on canes and on spur pruned vines over the spring.
Primary bud necrosis (PBN) is basically the death of the primary bud by either physiological or developmental injury.
It can go undetected because the surviving secondary buds may shoot and produce a normal canopy – but fruitfulness is usually reduced.
Shiraz is thought to be particularly susceptible to PBN.
In most years we don’t see the primary bud death but in exceptional years it tends to stick out – what can be done? The first step is to do some bud dissection in the winter to look at the condition of the inflorescence primordial in the bud. Bud dissecting will show if bud mite is a problem and will help rule in or out this as an issue. Examine the nutrition programme and work out if small quantities of broad spectrum fertilisers can help.
It is also useful to think about the formation of the inflorescence primordia – the process starts in year 1 and is completed in the spring of year 2 so any improvements / changes need to be in place for 2 years before results can be seen.
Looking at these issues as they are now – it would be important to consider post harvest irrigation
3. Soil Management
The times are drier than we think. Dig a hole – its dry at depth. Frosts tend to be worse when the sub soils are dry – apart from the mile high cover crop and all those under vine weeds lifting the height of the frost.
So mow, cultivate, roll the mid row areas to eliminate competition between the vine and the mid row sward for moisture and nutrients.
The vineyard should look a picture at the moment – neat and tidy.
Spot spray any escape weeds
I was talking about how dry it was in my region recently – our dams have not filled at all this winter – but I have had my feet wet longer & more often this year than in other years as I have moved around vineyards.
But it is dry and I was speculating about applying a pre flowering irrigation. My reservation is that irrigation this early will increase shoot growth and increase the crop potential and this could give problems later if water for irrigation becomes an issue or we apply RDI strategies later in the season.
Still it is time to flush end lines and sub mains and clean filters at the pump and in each block.
With the cold causing some early growth issues maybe a bit of nutrition is required to lift the leaf colour.
5. Vineyard Development
The planting of vines can occur from winter until after the frost period. For me November is around the end of planting but if you are using “green plants’ – vines that have been grown and planted in 1 year – November is when you get it done.
Using green plants has its risks so ensure the irrigation system is in place and working and that you have vine guards to place over the vines as you plant – the vines can’t dry out or they die! and that’s an expensive option.
Don’t be afraid to apply heaps of water and a bit of nitrogen
It’s a big month for meetings is November. We are looking to sort out the Germplasm future for Australia – see the Summary of a Review of Grapevine germplasm collections in Australia (GWR 1112)
I was reading in the Am J Enol. Vitic. 64:2 (2013) AN ARTICLE “ A statistical model to estimate bud fruitfulness in Pinot Noir’ by Jones, Lee and Wilson where they note “Grape yields … show the greatest source of seasonal variation to be bunch number per vine, accounting for ~ 60% of the variation, with berries per bunch the next greatest source of yield variation”
It is timely to count bunches per metre (or per vine) around now to produce your first crop estimate. Using last years final bunch weight a yield estimate can be made that is pretty good.
Pest and Disease
Maintain fungicide programme emphasis ensuring the bunches are clean and apply bunch closure sprays as required. – think bunch rots monitor for LBAM
Petiole sampling at 80% flowering
1st wire lift
Shoot thin and or fruit thin as required
Finish desucker process
Nearly time to complete planting and replants,
Place grow guards on small replants,
Check thro your nutrition programme – are you up to date?
Slash rows and headlands and waterways
Spot spray, mow or cultivate escape weeds
Irrigation programme are your devices in order?
– how much water, when
– Fertigation – do you have good reason to apply fertilisers?
1st yield estimation (bunch count) should be made
Thought for the Month.
Summer vine management
Managing vineyards in summer for high quality grape production can be a complicated process – especially in cool climate vineyards.
It is a time when vineyard variability can have a significant influence on the quality and yield of the grapes produced depending on what we do as growers.
In establishing what processes to undertake it is important that what we do we measure because if you can’t measure what you do you can’t manage it.
This article is about the tools available for managing variation and quality indicators in the vineyard.
Kristic et al (2001) found the typical between vine and bunch variability in a number of wine grape quality parameters as:-
Quality parameter Between vine variability Between bunch variability
Brix 4 – 5 % 5 – 9 %
pH 3 – 4 % 3 – 5 %
T.A. (g/l) 10 – 12 % 7 – 17 %
Berry weight (g) 6 – 20 % 10 – 15 %
Colour (mg/g f.w) 13 – 18 % 12 – 14 %
Polics (au/g fw) 13 – 17 % 8 – 12 %
In recent years a number of assessment sheets have been designed that establish a range of standards for vine measurements.
Smart (S.Afr. JEnol Vitic Vol 11, No 1. 1990) proposed a set of measures that have become standard for grapevines. The score sheet Smart constructed from his research established what is worth measuring and enables us to build a science based profile of standards for our vineyards that increase in relevance over time.
The findings of Smart and others found that :
– yield per vine was significantly positively correlated to berry weigh and bunch weight;
– fruit exposure and berry colour were significantly negatively related to a dapple – direct light scale;
– berry colour was significantly positively related to percent leaf functioning;
– sugar / acid balance and malic acid were significantly positively correlated to berry weight in Chardonnay;
– bunch weight was significantly positively related to flavour and sugar / acid balance;
– fruit weigh to pruning weight ratio between 5 and 10;
– low fruit exposure was a desirable target with 40 % thought ideal
To achieve the target parameters outlined above and to meet the “ideal” vine balance basic information is required to be collected. The results increase the relevance of the data as they accumulate over the years.
The key parameters for vine balance that require recording include:-
– at pruning where shoots per vine, bud number retained and pruning weight is recorded;
– in late spring when shots per vine and bunches per vine are recorded;
– at harvest where bunches per vine, bunch weight, Brix, T.A, pH and yield per vine are recorded.
– After harvest when the ratio of yield to pruning weight and yield per metre row are recorded.
Decisions that affects the vine parameters
As grape growers we choose a vineyard sited based on a number of prejudices. Primarily these prejudices involve where we want to live and what we know of a particular wine region. Once the region is selected the more difficult task of choosing a site is undertaken with particular emphasis in slope, soil, macro-climate then choosing what varieties to plant where on the site is undertaken. To complicate the decision making after establishing the variety is whether to use rootstocks and then what rootstock in which situation with which soil needs to be decided. Both these decisions will have long term influence on the viability of the vineyard and the growth habit of the vine. To add complexity upon complexity decisions involving planting density (row spacing and vine spacing), trellis design and irrigation type need to be made.
Each one of these decisions will affect how your vines grow – taken as individual choices and, when grouped together, these individual choices will influence all the growth parameters that can be measured in the vineyard.
Manipulations that you can undertake to influence vine parameters
1. Pruning is often describes as the first level of crop control. Hard pruning will invigorate the shoots compared to lighter pruning. Hence choice of pruning will affect quality parameters and influence what needs to be undertaken during the summer months to optimise grape quality. Getting the grapevines to express their natural vigour based on what you are trying to achieve will depend on experience and experimentation in your vineyard.
2. Soil management techniques can delete soil moisture levels or can reduce soil water losses both of which will affect how a grapevine grows. Leaving a growing mid row sward will delete soil moisture levels which is appropriate to do in a high vigour situation but inappropriate in low vigour sites.
Individual vine growth can be increased by severe pruning in all situations. Vine growth will be decreased where high bud numbers are left at pruning
3. Shoot thinning can open the vine canopy and may improve grape quality. The process of shoot thinning is the removal of unwanted shoot growth from head, cordon and arms when shoots are short (15 – 20 cms).
Shoot thinning serves several roles:
o it can help produce optimal shoot spacing;
o it can reduce costs at pruning as spur positions are clearly identified;
o it can invigorate the remaining shoots and could induce a poorer set on remaining shoots;
o it can reduce high crop loads
o it can increase bunch and berry size
When applied at fruit set to retain 12 to 15 leaves it is a good method to achieve the desired canopy size and maintain quality as little to no compensation in growth occurs
4. Crop thinning is an expensive and time consuming process and is often
restricted to young vines and replants to manage crop levels and ensure crops ripen adequately.
Crop thinning removes excess grape clusters to ensure remaining clusters ripen in a timely manner. The process usually is preformed at veraison by removing green clusters and any second crop however the best quality comes when the vines are in balance.
Where crop thinning is a bandaid process deemed necessary where the vine is growing wrong – wrong rootstock, variety, pruning, trellis, planting space or too much fertiliser for example.
Researchers have shown that crop thinning is appropriate where there are short shoots carrying 2 or 3 bunches of reasonable size and where there is excessively high yields and a dramatic (50 %) thinning is likely to cause sufficient change for an improvement in quality.
As a general statement crop thinning is delayed until after berry set to decrease the risk of the vine compensating by means of an increase in the number of bunches set as well as berry and bunch mass increases, resulting in only a small reduction in yield.
It can be noted however that crop removal around flowering can be a good practice in reliably high yielding varieties like Viognier when it is easier to pinch bunches off shoots rather than later in the season when it is necessary to cut bunches off.
5. Leaf removal is a practice undertaken either early (when berries are pea size) and / or late (just prior to veraison).
It is unnecessary in most years with most varieties in most Australian wine regions. It is certainly of no benefit to non vigourous vines.
Leaf removal is often undertaken in December / January period in cooler regions as a remedial tool for improving air and light penetration into the fruit zone. The zone just above the fruit level is the main target area and most useful in high humidity high rainfall years.
As a rough guide in cooler climates 12 to 15 leaves per shoot are the aim for optimum grape quality.
6. Foliage management involves lifting a pair of wires above the cordon area to bind canopy in mainly an upward direction. Some modern trellis practices (Scott Henry) involve both upward and downward wire movements undertaken to open the fruiting zone to higher levels of sun and air.
The first wire lift is done just before flowering when shoots are around 300 cm in length. A second lift occurs approximately 4 to 6 weeks later.
The idea of lifting wires is to create an ideal 1.5 leaf layer density across the fruit zone of a vertical trellis reducing the need to undertake any leaf removal or crop thinning.
Lifting wires is a relatively cheap process that meets the needs of most vineyards in most years.
7. Irrigation practices will affect the crop level in a vineyard. In hot regions growers are more likely to increase water applied, as irrigation, in low price years to increase yields. In cooler regions irrigation water is used to maintain soil moisture levels to a calculated level for historical grape quality requirements.
Irrigation practices are more a fine tuning practice based on water use history for a particular variety growing in a particular soil.
A point often overlooked is that different varieties either on own roots or with rootstocks will vary in their water use. Similarly white varieties may require more water applications than red varieties to achieve the desired quality levels.
8. Fertilisers require care when applied to grapevines. Grapevines don’t appear to require large quantities of fertilisers to produce adequate crops of reasonable quality.
On some soils and in some wine regions the addition of a particular fertiliser or group of fertilizers maybe required to correct any identified deficiency within the vine.
The use of petiole sampling and / or sap analysis assists in identifying issues that may occur in the grapevine however it is thought necessary to act only after a history of several years shows a trend before acting to counter a deficiency or toxicity identified in grapevines.
Many forms of fertilizers are available for use in agriculture but it is experience on your site with fertilisers that demonstrate improvements in your grapevine performance that should guide your fertiliser use.
9. The most important decision a grower or winemaker can make is the harvest date as this decision will affect the quality of the wine produced. The winemaker, in choosing a harvest date, will be trying to optimise the compositional characteristics of the fruit to suited their desired winemaking style.
Science tells us the harvest date alone accounts for 42% of the variability in quality ratings hence there is often tension at harvest as winemakers aim to increase hang time for their wine style requirements and growers want to harvest their grapes as soon as basic ripeness requirements are meet.
Without a common vocabulary for winemakers and growers to use to describe varietal aromas and purchaser “style” requirements these tensions often high around harvest. The conclusion one can make from this is clear – the selection of harvest date requires a lot more science and less subjective opinion however every winemaker has “style” requirements that are different from other winemakers.
Clearly summer is a high activity time in the vineyard where viticultural practices can impact on wine style and quality perceptions.
Grape growing involves an unlimited combination of variables many of which the grower has no control over.
The concept that we need to measure what we do in the vineyard to be able to adequately manage the vines to produce optimum crops of high quality fruit has never been more true.
Many of our viticultural practices will affect how our grapes grow so the challenge is to manipulate the variables to come up with the things we are all ultimately striving for – a good glass of wine.
The focus is on the end product – that’s where it all starts.
To your ongoing passion for viticulture.