July 2008 Douro Insider

As one would have expected for a Portuguese July, it certainly got off to a hot start, but less predictably it was also rather muggy.  Proximity to the river increases evaporation and obviously exacerbates the humidity.  Meanwhile, as the  water warms up, algae gradually turn the Douro a  slightly sinister greenish shade.  But the summer that we all thought had finally arrived at the end of June turned out to be fairly short-lived or perhaps yet another false start.  The high temperatures soon evaporated and we then had another few days of what can only be considered very cool weather for the time of year.  One or two days barely crept above 20º C, and the nights were, frankly, cold.  Daily minimums below 10º are not usually part of the script.  In spite of the cool temperatures it was still an exceptionally dusty month (much worse even than the usual gritty situation) as the rain held off and some gusty winds desiccated the topsoil.  After the second week things began to heat up again, peaking around the 20th when southerly winds brought some real African heat to Iberia.  It then began to tail off once more, and we had a dodgy end of month, especially the last day.  This gave us a rough pattern of one cool week, two warm weeks, and then another cool week to finish off.

In Pinhão the mean temperature was just 23.6º – or more than 1º cooler than the long-term average of 24.7º.  The absolute range was therefore rather broad, running from 10.7º all the way up to 41.3º.  Precipitation was registered at a punctilious but utterly inconsequential 0.2 mm.  This quantity would of course never even have been detectable in the days before electronic weather stations.  It compares unfavourably with the monthly mean of 14 mm.  The cumulative total rainfall for the year so far is now exactly back on par, having been corrected downwards by July, so we are only 6 mm short of the average value with a total of 363 mm having fallen since the 1st January.

The situation in the vineyards was relatively relaxed in one sense, but very busy in another.  The cool spring meant that the annual lifecycle of the vines was unravelling considerably slower than normal and thus there was plenty of time for carrying out the usual operations, but on the other hand there was not enough of the hot and dry weather that slows down growth and gives us breathing space.  Helped by the fact that there is no water stress to speak of so far, this means that vegetative growth is vigorous and canopy management is therefore complicated.  Additionally, the pressure from disease is fairly high due to the unstable climatic conditions and so it is essential that the shoot positioning and trimming be kept up to date to ensure effective spray penetration should it be decided that anti-fungal treatments are required.

We had a relatively early budburst this year (the winter was not especially cold) but it was followed by late flowering, later fruit set and now veraison has been even more delayed.  Normally speaking the earliest bunches in the Douro Superior have 50 % coloured berries by about the 15th – 20th July, with the average date for the more central vineyards coming very close to the end of the month.  This year the grapes were still a long way off changing colour when the month ended.  Typically veraison would therefore have occurred well into August for most producers, suggesting that we are between 10 and 14 days behind the schedule expected of a normal year.  Without wishing to make premature predictions, this obviously hints that we can expect a late harvest this year.

One of the effects that this unusual climate has had is that it has created some difficulty in following the reproductive cycles of the insect pests of the vine.  The weather has provoked rather irregular breeding patterns making it much harder to time interventions correctly.  The cicadela especially has caused visible problems in vineyards all across the Douro where some growers have not kept a close enough eye on it.  This sap-sucking leafhopper has been attacking varieties where it would never have been expected in the past and the implication that it appears to be extending its range is a little worrying.  On the bright side, the fact that the vines have plenty of leaves and are not undergoing any significant water stress has meant that (in spite of appearances) very little actual damage has been done.  The red hue that leaves take on when attacked often appears much worse than it is.

Activities in the quintas are often as much a question of housekeeping as anything else, given that holidays are generally taken by the workers during August and the vineyards must be left in an impeccable state to see the month through.  The major activity on the books absolutely everywhere was desponta (shoot tipping).  When timed correctly the removal of the growing tips coincides with the start of sugar accumulation in the berries (at veraison) and, coupled with a little light water stress, should stop the shoots from growing.  From this point onwards, therefore, all of the vines’ energies will be directed into ripening the crop and not producing more foliage.  Despontas are usually carried out by machine, but in older vineyards where tractors cannot enter or the trellis is not up to the job then  manual shoot tipping also occurs.  In very old vines it might be more usual to roll the shoots flat along the top wire, the act of pointing the shoot tip down having a similar effect in stopping its growth and ensuring that it is no longer a significant nutrient sink.  Shoot thinning and shoot positioning still occurred at one or two quintas in July although by this stage virtually all canopy management involves physically cutting off the growing tips.

It was also considered a wise idea across the region to carry out a last preventative treatment to protect the fruit until the hot weather and toughening grape skins makes disease development almost impossible.  It is not common to use elemental sulphur, (applied as a powder) at this time of year because there is a risk that the berries and the leaves of the vines might burn should the air temperature exceed about 30 – 32º at the time of application, or within a couple of hours afterwards.  Leaf burn from wettable sulphur (in an aqueous suspension) is extremely unlikely to occur, however, especially as the dosage is much lower so this alternative is favoured.  In any case, above about 35º powdery mildew is unable to develop, so any applications are carried out more for safety’s sake than because of any real risk.

Leaving the vineyards in order before the summer holidays may well involve some sort of weed control – again taking advantage of the fact that no new growth will be forthcoming given the summer temperatures and ongoing drought.  Thus there were many instances of ploughing and of course the clearing of the banks between the terraces can be carried out manually with strimmers or hoes if the weed infestations are not too intense.

Young vines obviously need plenty of attention too, given their underdeveloped root systems and the harsh Douro climate.  Thus at every quinta where this year saw a new plantation installed, the month of July witnessed plenty of hand watering going on as well.