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Section 4.7: Post-grafting Management of Vines – Harvesting First Crop and Strike Rates

Swim Admin

“Field grafting is a great way to change variety or clone and quickly return a vineyard to full productive potential. Field grafters are only partly responsible for the success or failure of field grafting. Understanding what preparation and follow-up is required as a grower to influence the final strike rate is critical. VitiSense provides all the information, techniques, demonstrations and explanations and to ensure your field grafting experience is a positive one”.

Expect a good yield in the first year after grafting if the vines have been well trained and managed. As the vines have had good light exposure a the new cordons are generally replacing older unproductive cordons, the yield can be very high compared with previous harvests. In some regions with some varieties it is prudent to manage the high yields as you would an established vine to avoid any issues with delayed harvest of not reaching full maturity specifications of the winery. 

How the first crop after grafting is harvested really depends on the growth (uniformity and strength), training, yield and strike rate. In most situations, it is possible to machine harvest the first crop carefully with no harm to the grafts. Generally after the first seasons growth of grafted shoot, the callusing has occurred and lignified canes are wrapped on the wire. There is enough strength in the callus union between cordon and trunk at this time to withstand a machine harvester. The only time I have seen a problem with broken grafted canes in the first harvest was where the vines had a pre-existing Crown Gall infection which compromised the callusing. 

Strike Rates

The strike rate is dependent on not only the skill of the grafters, tapers but also the preparation and followup management of the vineyard. These are the “controllable” factors and then there are the “uncontrollable” factors the most significant being seasonal weather events. 

The strike rate is rarely 100% and due to many variables controlled and uncontrolled, it is very rare for a grafting contractor to offer a guarantee without may conditions. Understanding the controllable factors and being intuitive about the uncontrollable factors is the best way to realise grafting success through high strike rates. 

Controllable Factors Influencing Strike Rate 

  • Timing of grafting – Experienced grafters attempt to time their visits to perform the work around optimal seasonal conditions although this is not always practical. 
  • Grafting contractor – an experienced grafting contractor should be prioritised. Check references. Follow up communication and availability for regrafts is also important for a good strike rate. 
  • Vineyard management – Level of experience with grafting. Familiarity with the preparation and followup management required for a successful take? 
  • Virus status – Failure to test or poor sampling technique for virus testing samples. 
  • Rootstock variety and trunk health – Semillon is a difficult variety to graft and rarely has a high initial take. Trunk disease/s have a big impact on strike rates and future growth and performance post grafting. Abandoned vineyards do not make good candidates for grafting if they have not been irrigated or received adequate nutrients the season before grafting. 
  • Vine preparation – trunk health assessment to cut below disease, cordon removal using mulchers can split trunks, failure to paint wounds before rain can exacerbate trunk disease issues in the future. 
  • Budwood – quality (size, virus status), source block/nursery, handling, storage and rehydration. 
  • Water management – drainage, irrigation, soil type. Over watering and under watering can effect strike rates. Well drained soils are preferred. 
  • Weed management – Uncontrolled weeds growing into the cordon area or competing with vines for water in dry seasons. They also harbour chewing insect pests which can damage grafted buds. 
  • Nutrition – Healthy vines have better strike rates. Carbohydrate reserves in the trunk are important for strike rates and callusing to occur. 
  • Midrow management – maintaining cover in the midrow 
  • Pest and disease management – Incidence and severity of pest and disease damage will vary depending on the seasonal conditions and IPM management strategy. Grafted shoots are differeent to established vineyards and should be managed accordingly to avoid damage resulting in low strike rates. 

Uncontrollable Factors Influencing Strike Rate

  • Weather – too much rain, not enough humidity, extreme heat, hail, wind, snow, frost all have an influence on how the final strike rate will be for grafting.
  • Vines – How vines grow is largely dependent on the season and sometimes they grow better in some years than others. 

Case Study

“I once had a grower complaining about the growth of his grafts compared to his relatives vineyard we had grafted down the road. Both vineyards were in line of sight of each other. He said the poor growth was due to our skill (lack of) as grafters which was the problem. I explained that we had done nothing different between the vineyards with both grafted within days of each other and by the same members of my team. What he failed to realise was that his relative hadn’t abandoned his vineyard the year before grafting and turned the water off in Summer to stress the vines as well as not fertilising it for years. His relative also scared away the parrots and kangaroos to avoid the shoot damage that he was experiencing and spent double the time training and responding to the weather to irirgate and feed his vines in a timely manner”.