Jobs for July – Vineyard

Early signs suggest there could be some big crops this season, so Hutchinsons agronomist, Will Robinson, highlights five ways to help vines deliver on that promise over coming weeks ...

1. Manage canopies

Trimming the tops and sides of vines contains excess growth and ensures adequate light and air circulation through summer, while targeted leaf stripping further aids UV light penetration, improving bunch ripening and potentially reducing disease risk.

There are two schools of thought on the best timing for leaf stripping. One is to do both sides of the vine at late flowering, exposing developing berries to UV, which improves skin thickness and resilience to sunburn. Mechanical stripping of both sides is relatively quick, however if stripping by hand, it can sometimes be more cost-effective to just do the side exposed to morning sun first, and, if time allows, return to the other side later.

Another approach is to wait until late August, when sunburn risk is declining, then expose fruit to aid ripening and anthocyanin accumulation in the skins. Maintaining a full canopy through July and August can increase humidity though, so close attention to topping, trimming, and spray applications is needed, especially if vines are growing vigorously.

2. Feed crop potential

Crop potential looks very good in many vineyards, possibly in line with 2018 and 2022, so ensure canopies can feed this. A rough rule of thumb is to aim for 50% leaf, 30% bunch and 20% gaps.

When leaf stripping, only remove enough leaf to expose the bunch, leaving sufficient foliage to ripen the full fruiting potential. Be particularly careful if grazing sheep in the vineyard, as they will eat every leaf they can reach.

Tailor nutritional requirements to the results of leaf petiole analysis done at flowering. If vines are not fed well enough via the soil, or leaf, crops may be good this year, but could have more blind buds next season because there isn’t the right nutritional balance in the vine to support consistent yields.

Given the high yield potential, some growers with young vines may be tempted to take a harvest from second-year growth. This is still very early, but if taking a crop, limit it to one bunch per cane at most, and maintain a good feed programme to avoid compromising future vigour.

3. Control diseases

New extension growth is particularly susceptible to disease, given it has missed the protection afforded by earlier fungicides. Trimming out vulnerable material, and well-timed, targeted fungicides, is key to managing the risks.

We saw last year more Downy mildew on the laterals of primary shoots, particularly where growers stuck to a rigid two-week spray programme, so be flexible, and consider an intermediate treatment (e.g. sulphur + copper) mid-way between conventional treatments to maximise protection if risk dictates.

Some protection, and good canopy management, will also be necessary on resistant PIWI varieties in high-pressure situations.

Removing water shoots can help reduce the risk of Downy mildew spores splashing up onto the main fruiting canopy during heavy rain.

Powdery mildew pressure was high during the spring, and must be kept under control by maintaining a good programme. Unsettled weather during flowering will increase latent Botrytis risk. Mitigate this with good light penetration and airflow, plus a robust fungicide programme, based around actives such as pyrimethanil or fenhexamid, both of which can volatilise in warm conditions, potentially improving coverage through the bunch. Biological products, such Amylo-X also offer an alternative to synthetic chemicals.

Watch for signs of early bunch stem necrosis, as risk could be greater with large crop potential. Exact causes are unclear, but we have seen in previous dry years that extra calcium pre-flowering and post-flowering can help build cell walls and reduce risk.

4. Monitor pests

So far, it has been a high-pressure year for insect pests given the warm, dry spring, so continue monitoring for the likes of light brown apple moth, cutworm, and winter moth. Nut scale (Eulecanium tiliae) has also been increasing, but is usually pruned out, or can be easily knocked off the vine.

Vine leaf blister mite is also more prevalent, especially where growers missed the first sulphur spray. There is little that can be done once blisters have formed, as control focuses on when insects are crawling, usually from bud burst to the three-five leaf timing.

5. Plan for next year

It is worth remembering that next season’s flower initiation is influenced by sunlight penetration onto canes that are going to be saved, so ensuring those canes are in a good position and not tucked behind others will help.

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