May 2011 Douro Insider

Although generally very warm, April ended on something of a sour note with a quite wet last two days. May, however, saw conditions swiftly returning to earlier form. With the exception of the first day, it basically didn’t rain at all in many places and the daily maximum temperatures set off on a steep upward trajectory almost immediately. With the clear skies and longer hours of sun each day it got hotter and hotter, so that by about the 10th we had passed 30º C, still rising. With most of week two in the thirties it was already clear that we were looking forward to an unseasonably hot average for the second consecutive month. The unmistakable feeling that summer was setting upon us was further reinforced as soon as the hot winds that blow up the Douro valley started to be felt at the end of the day. These strong, dehydrating gusts pick up towards dusk, but only in the summer months, and readily bring on a peculiar kind of thirst which can only be slaked by reacquainting oneself with an icy glass of Alex and Johann’s most successful joint venture, indispensably garnished with a decently-sized slice of one of Malvedos’s juiciest lemons.

Conditions started to change a little around about the 11th, becoming more unsettled. In practice this meant that although the heat continued (or even increased), it was now joined by a certain threatening heaviness in the air. It was by turns gusty and thundery, with some lightning on occasions, but it seemed that storms were always brooding without really coming to fruition. As a result, no rain of any consequence fell on most of the Douro. This increasing humidity is a friend of oídio, and we had to be on our guards. From a disease-prevention perspective things were further complicated because, on occasions, temperatures still dropped enough at night to allow dews to form, in spite of the high daytime temperatures. If this kind of humidity gets into the bunches it can be extremely dangerous at this stage of the phenological cycle. In addition, the fact that it was thundery immediately after flowering caused some problems with fruit set, particularly in the Barroca which suffered quite badly from desavinho this year.

In retrospect the weather in May was all about spatial heterogeneity, as much in the Douro as in the rest of the country. It is almost impossible to generalise as the wildly disparate figures recorded in different parts of the region showed, both in terms of temperatures and precipitation. On a national scale there were some impressive but localised downpours – in the Algarve various towns were hit badly by torrential rain and on one occasion access to some parts of Faro itself was completely cut off, with the streets under more than a metre of flood waters. There was also flooding in Lamego on the 25th (in this instance accompanied by landslides too), a product of the sporadic thunderstorms and transient lightning downpours that characterised the month. In other places the damage was yet more severe: a hailstorm on the 23rd caused considerable (but again, mercifully localised) destruction of fruit in the vineyards of the Soutelo / Nagoselo area. Reports came in of seeing hailstones as large as cherries (which, incidentally, were becoming deliciously ripe around the same time). The violent storms continued right up until the end of the month, turning the gradually-clearing colour of the Douro back to brown again (especially just downriver of its tributaries). And to round everything off nicely, another Icelandic ash cloud came along to close airports in northern Europe although disruption in Portugal was obviously only indirect.

In spite of the local variation there were certain common meteorological themes for the country as a whole. The Instituto de Meteorologia pronounced it the warmest May since 1931, with temperatures around three degrees over the average. A glance at the graph below shows that in the case of Pinhão our numbers were at least consistent with the national situation: there the average temperature, at 20.5º, was indeed the warmest on record for May (although our records are only forty-odd years old). It was also 3.1º degrees higher than the mean, and not even the hottest part of the Douro.

Pinhão was, however, the driest part of the Douro (by quite a long way) with virtually no precipitation to register. The total that fell there was less than a quarter of the expected amount, at just 9 mm (compared with the average of 54 mm). Bear in mind that this month’s precipitation figures showed huge variation from town to town; some parts of the Douro recorded an almost ten-fold difference in rainfall in the space of just a few kilometres. This is now the fifth consecutive month of below average rainfall, meaning that our cumulative total for the year (on the second graph) remains resolutely under the mean for this point in the growing season. The actual figure is now 218 mm and the corresponding mean is 321 mm, indicating a shortfall of more than 30 %.

This is a slight worry from a viticultural point of view since the extreme temperatures of April and May will have compounded the problem of low rainfall through increased evaporation of soil water. The early onset of the summer winds does not help either. We can only hope that the high relative humidity has at least kept evapotranspiration by the vines to a tolerable minimum. It is clearly slightly early to be making predictions, but another hot summer could spell danger for the grapes again, as it did back in 2009.

The first viticultural point of note this month is one of a phenological nature, an area which has been generating particular interest recently with the vines displaying some very surprising behaviour in the Douro. Our ‘official’ flowering date this year was the 11th May – a full fortnight earlier than in 2010 and still well ahead of our average date of the 23rd. Fruit set obviously came not long after, this year’s average date for the main varieties being recorded on the 20th May, still a long way earlier than average (the 29th), and 10 days before the same point was reached in 2010. Fruit set was good in general, thanks in part to the basically fine and warm weather we experienced around that time. As was mentioned earlier, however, there were some signs of desavinho (or more specifically, ‘coulure’ or ‘shatter’) in the Tinta Barroca which is not a variety that often suffers from this problem. Then, not far behind the vines, the olive trees also came into flower around mid-month.

After the warmth of April, another hot month kept things in the vineyards running along at an almost impossible rate. Canopy management was of vital importance and took up most of the month’s work in one form or another. Not only is it critical to have a well-aerated hedge to keep the humidity levels down in the bunch zone, but correct shoot positioning is also vital for the effectiveness of phytosanitary treatments. As a result we were almost continuously tucking the shoots between the wires, and thinning out unnecessary growth. These operations were usually interspersed with fungicidal treatments, particularly against downy mildew. This fungus is having something of a bumper year so far; conditions have favoured its development to such a degree that many of the products that we use to protect the vines against infection are considerably reduced in their effectiveness. Whereas in normal years some of the chemicals might be good for almost two weeks of coverage, this spring saw that figure reduced to around half that. In the majority of our quintas this is less time than it takes to carry out a round of treatments so we found ourselves in a clearly uncomfortable predicament.

Downy mildew can have a devastating effect on the crop size, reducing yields to nothing in serious cases. However, as it results in the complete or partial abortion of the vine flowers and / or bunches (which then dry up and drop off), its effects are never seen in the adega. Years with even major downy mildew infections therefore have absolutely no detrimental effects on the quality of the wines that are made. The damage can be both very localised or very widespread but in general the company quintas were not badly hit, principally due to good timing with the very first treatment which reduced the intensity of secondary infections. Contrasting with our relatively fortunate position, sad stories came in from across the Douro that some farmers had lost virtually their entire harvests already, with downy mildew and hail both conspiring. It certainly will not be as large a vintage for the region (and perhaps also for the country as a whole) as some people had been predicting a few weeks ago.

With a fairly desperate struggle controlling the vegetative expression of the vines and treating (both preventatively and curatively) against fungal diseases, there was little time for other activities in May. Those who were able to find a spare moment managed to fit in some weed clearing since it is not just the vines that the hot weather favours, and it hasn’t been easy to keep the less desirable plants under control this spring. Most properties also found that the cover crops were in need of mowing this month for the same reason.

An interesting indication of how advanced the vines are this year is the fact that many quintas already registered the start of the first round of despontas this month. This practice (hedging) is only carried out once the majority of the shoots have reached almost a foot above the top trellis wire. In only two months since budburst we have therefore had a metre of growth. The lateral trimming is also important for ensuring the smooth passage of machinery between the rows of vines, and for exposing the bunch zone both to sunlight and to the spray of pesticide treatments.

There was clearly little time for much else to be done during the course of the month but that did not mean that the new plantations could be abandoned. One very important procedure involves digging the caldeiras (little depressions around the base of each rootling) which will be essential when it comes to watering them during the summer. The way the weather has been so far suggests that this might be required sooner rather than later. Normally it is best to carry out some stone clearing (or crushing) first as this can be inconvenient to do once the caldeiras have been dug. And immediately afterwards is the best time to get started with putting up the trellis – the subsidies require this to be in place by the end of July.