Grape Netting Project

Last winter, I was approached by Doug Whitty, about doing a netting project at a vineyard on 7th Street. It had particularly bad bird pressure because of a hydro line and bush. Doug was reluctant to use cannons, because of the proximity of neighbours. He had been speaking to a company called Gintec, who specializes in producing and installing shade cloth over ginseng in the Norfolk County area. You might have seen their booth at the Convention at Brock University this winter. I spoke with Helen Fisher and we set up a small, applied research project with netting over only the fruiting zone of the vines. Here’s a brief update.

The black netting is UV-treated, very tough, anchored on the end posts, and attached to either the top or second wire on the Pendelbogen training system. Special clips are used. The netting comes in long rolls and is rolled down and installed on one side of the row, then the other (Figure 1). Special clips are used to attach it to the wires. The mesh openings are about 4 mm x 7 mm. The net is installed permanently, rolled up on the top wire over the winter, rolled back down in the summer. The net is not cheap, but because it lasts so long, it is hoped to spread the capital cost over several years. Gintec has been investigating several labour saving ideas to reduce the work to install and remove it each year, plus investigating how to simplify things at harvest.

There are four treatments that we tried on which we are monitoring several test vines:

• Control, with no netting at all
• 1.0 m wide net attached to the 2^nd wire, and pulled down over the vines early in the season in May before there is any growth (Figure 1 was taken in May)
• 1.0 m wide net attached to the 2^nd wire, and pulled down over the vines between bloom and veraison in July when there is lots of growth (Figure 2)
• 1.5 m wide net attached to the top wire, and pulled down over the vines just before veraison and expected bird pressure in late August

Figure 1: 1.0 m wide net attached to the 2^nd wire, and pulled down over the vines early in the season

Figure 2: 1.0 m wide net attached to the 2^nd wire, and pulled down over the vines between bloom and veraison

Although the main objective was to see if bird damage could be controlled in a cost-effective manner, there are other things that we are watching including; any positive or negative effects on the vines and grapes through vine training, abrasion, shading from sunburn, spray drift, fruit quality, and yields.

It is too early to tell if these nets will work, but early indications are interesting. The nets installed in May did a great job of controlling growth tightly against the row, forcing shoots high and upward between the nets. However, because they were on so early, there were a few vines and bunches that grew through the net, and will create some challenges during net removal before harvest. Leaves also appear to be larger under the nets because of the shading effect. Doug seems to think that sprays are contained better under the nets.

The nets pulled down over the vines in July also helped push shoots upwards, although it was more challenging to pull the nets down because of all the growth, and a lot of vine tucking was needed.

The nets that were rolled up on the top wire all summer were pulled down last in late August (Figure 3). These nets created some shading and obstruction for the vines, forcing them to grow upwards, then ‘flopping’ outwards towards the middle of the row.

Figure 3: The nets that were rolled up on the top wire all summer were pulled down last in late August

There is little doubt in our minds that the net will control birds. The issue is whether the cost of the netting can be justified, and whether there are other benefits that can be found to help offset these costs. We’ll be taking yields, seeing how sugars may, or may not, be affected by shading, and do a full cost-analysis of this system over the fall and winter.

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