Preparing for the spring in the vineyard

It has been a long cold winter, and as the grape vines start to de-acclimate it is time to start thinking about the long list of things that needs to be done for the upcoming season.

When is it too late to finish dormant pruning and tying?

The goal is to finish pruning and tying the vines before the buds begin to swell. Once the buds begin to swell and the shoots have started coming out manipulation of the vine and shoots can knock off shoots resulting in yield reductions.

When should the vines be unburied? Once buds start to swell, they become more susceptible to cold than when they are dormant. If temperatures begin to increase and budburst begins while the vines are buried, bacteria will infect the buds resulting in reduced yields.

When should dehilling start?

De-hilling of the vines in the spring occurs after the threat of extreme weather, and before the application of pre-emergence herbicides.

What should I be doing with my sprayer to ensure it is getting good coverage and protecting my crop?

At the beginning of each season it is important to tune up your sprayer and ensure that it is calibrated to ensure good coverage. For more information on sprayer maintenance in the spring refer to Hort Matters newsletter article, Airblast Sprayer Start-up Tips.

When should you check buds for winter survival?

As those of you who have been monitoring the CCOVI bud hardiness website (http://www.ccovi.ca/vine-alert/bud-survival) know, the grape vines are slowly starting to de-acclimate in preparation for bud burst. Bud survival can be assessed by cutting buds laterally and looking for green tissue (a sign of live buds). Each grape bud nodule contains three buds, primary, secondary and tertiary. The primary and secondary buds produce fruit, with the secondary buds produce smaller and less fruitful bunches. The tertiary buds which are the most cold tolerant produce only leaves. Check bud survival in the late spring when pruning begins and use these assessments to make adjustments when pruning. Varieties that were pruned early and extra canes or buds were left as insurance can be re-pruned to remove extra buds in late spring. It won't be clear how much winter damage occurred until the buds start growing. Examples of live and dead grape buds can be found at: http://www.colostate.edu/programs/wcrc/pubs/viticulture/EvaluatingBudDamage.pdf.

What are some tips on using my wind machine to protect my crop from frost?

The CCOVI vine alert website will continue to provide growers with information about the vulnerability of the crop to cold temperatures and frost. Some useful tips on best management practices with wind machines can be found in the OMAF and MRA Factsheet # 10-045, Wind Machines for Minimizing Cold Injury to Horticultural Crops and a Tender Fruit Grape Vine article, Are you ready to operate your wind machine this spring?

When should shoot removal be done?

Shoot thinning is carried out in the spring when the new shoots have reached a length of approx. 10 to 30cm. While shoot removal is not essential, the canopy can become dense, increasing the potential for disease and making it a challenge to get good spray coverage. Shoot thinning can help to reduce crowding. The drawback to shoot thinning is that it causes more lateral shoots to grow on the remaining shoots because they get more light. However, the additional lateral shoots occur mostly above the clusters. During thinning remove all water shoots (unwanted shoots arising from the old fibrous wood of the trunk) unless they are needed for the development of the vine structure. Also remove any other infertile shoots without visible inflorescences, which emerge from the pruned fruiting cane. However, at least one near-stem new shoot must remain at each shoot position for the following winter pruning. If there are two or several shoots growing from one bud, the strongest one (with inflorescences) is retained, all others are removed. Shoots are removed by being rubbed off by applying some lateral pressure, or grasped at their base and pulled off. If necessary, shoot thinning can still be carried out in summer, however, the shoots are then usually cut off with a sharp knife instead of pulled off, due to the beginning lignification.

When should flower cluster thinning be done?

Flower cluster thinning (or removal of clusters) can be done at any time during the season, but the timing of when it is done has different affects. Flower cluster thinning is often performed prior to or during bloom. The benefits of doing it at this time is that it can be done quickly because it is easy to see the flowers, since the canopy is still developing. The early timing means it can be done at the same time as shoot thinning, reducing labour costs. Flower cluster thinning early enhances berry set in the remaining clusters, and reduces competition between the flowers resulting in increased berry size and weight at harvest in most varieties. In varieties with cluster weights less than 150 g, often yield compensation is insufficient to overcome the reduction in cluster numbers and cluster thinning does not increase yields in these varieties (ie. Gewurztraminer, Pinot noir, and Riesling) and their yields may even decrease. Benefits of flower cluster thinning include increased fruit soluble solids, flavour compounds, anthocyanins (colour) and possibly wine quality. The downside of flower cluster thinning is that the clusters can get tighter, causing issues with bunch rot. Thinning at this time can stimulate vine vigour resulting increased canopy shade, causing high titratable acidity.


For more information:
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E-mail: ag.info.omafra@ontario.ca