The harvest is of course the high point of the viticultural year, when Graham’s wine making team is hard at work bringing in the grapes and making our port wines. Not all of the grapes cut in September go into the wine, however: this is also the time of year when many of our research activities enter their final analysis phase. In any given season we may be conducting research on a half dozen viticultural concerns, such as optimum root stocks, vine clones, trellis systems, irrigation, cover crops, pest or disease control, or soil erosion.
Miles Edlmann, responsible for viticultural research and development, has designated vineyards in a number of sites for his experimental purposes, and he needs to collect his data – in other words, the grapes for analysis – one step ahead of the harvest team. For Miles, the harvest has already begun.
In the Douro, we are visited by the European Grapevine Moth, which has a special fondness for Touriga Francesa. As we at Graham’s are pretty fond of Touriga Francesa ourselves, for the intense floral aromatics and well balanced structure it brings to our wines, we object to sharing the crop with hungry caterpillars every summer. Three years ago Miles came up with a possible solution to the problem, and has been trialling the technique and analysing the data during each subsequent harvest. This year’s results are telling us we may have a solution.
Miles’s idea was to try to open up the Touriga Francesa bunches – which are normally very tightly packed, almost solid – to minimise the damage. If a caterpillar does get onto the bunch, the hope is he will find himself marooned on a single grape which is so far separated from its neighbours that the tiny caterpillar is unable to inch his way onto an adjacent grape to do more damage.
This particular experiment is being carried out at Quinta do Atalho, another Symington quinta which is not part of the Graham’s group of vineyards. Our riverside quintas (such as the five dedicated Graham’s properties) do not often experience trouble with the moth, whereas Atalho has a particular microclimate which makes it notoriously prone to this problem. By basing this experiment in an extreme situation, we are able to draw conclusions more easily as any differences will be more apparent when they do exist.
If you think trying hard to sequester caterpillars sounds a bit humorous – and we do too, sometimes – individually plucking and scrutinising 6,713 grapes in one afternoon is no joke. Miles and his team of oenological trainees cut 40 bunches of Touriga Francesa from the designated vineyard in the morning, half from vines treated to open up the bunches, half from control (untreated) vines. Back in the lab, the grape bunches were individually weighed and the berries plucked off one at a time, inspected and counted – caterpillar-damaged, undamaged, and immature grapes were counted separately. The bare stalks were then measured for both length and width, and the volume of the grapes from each bunch measured.
And – because they were there – we also counted the caterpillars: 89.
Our data from this year’s trial shows significantly less caterpillar damage on the treated bunches – this is a breakthrough in trying to control this pest.
In addition to isolating any caterpillars and the scope of their damage, opening up the grape bunches helps ensure the health of the crop in other ways: open bunches are less prone to mildew or botrytis, as both wind and sun can penetrate to ventilate and dry the grapes, and healthy grapes generally are less prone to attack from pests. Also, as Miles has observed before, the more sun on the grapes the better, as a moth egg, once fried in the sun, can’t hatch.
These experiments represent a substantial investment for Graham’s, in time, effort and resources, but are critical to ensure the future of our vineyards and the quality of our wines. The Douro is a unique terrain which remained isolated and remote long after many other major wine growing regions, and we have many so-far unheralded indigenous grape varieties, so there is still much to be learned. Whilst we keep abreast of research developments in other regions, and share information with colleagues in the viticultural community, ultimately we in the Douro are necessarily self-reliant in working out our own solutions to our often unique challenges.