Port anD the Douro 69systemic sprays. The number of treatments varies according to the year and the location of
the vineyard. In the Douro Superior two or three treatments will normally suffice, whereas
growers in the Baixo Corgo may have to spray their vineyards as many as eight times in a
damp spring and still find themselves fighting a losing battle. Most of the old densely planted
vineyards have to be sprayed by hand although in some years a number of larger properties
have used helicopters to treat the vines against oidium and mildew; these have now been
dispensed with due to high costs. Bunch rot (Botritys cinerea) is endemic throughout most
of the region, especially in old mixed vineyards with a high proportion of Tinta Amarela,
a variety that is particularly susceptible. This is controlled by spraying with calda bordelesa
(copper sulphate, known as ‘Bordeaux mixture’). But rot is most damaging when induced
by rain late in the growing season, by which time it is often too late to spray as chemical
residues might find their way into the wine. The 1993 and 2002 harvests were notorious for
producing poor quality pale wines, frequently tainted by rot.
The grape moth (cochylis and eudemis) can cause severe damage in the vineyard,
destroying buds or boring its way into ripe grapes, bringing on bunch rot. In the Douro
Superior a leaf-hopper known as cicadela has begun to be a serious problem at some
vineyards, damaging the leaves of the vine and reducing levels of photosynthesis. Tinta
Roriz and Tinto Cão seem to be the most susceptible varieties. Leaf hoppers are also the
vectors for bacterial diseases, among them Pierce’s Disease and Flavescence Dorée, neither
of which have thankfully been identified so far in the Douro.
Viral diseases introduced from the rootstock are a continuing problem, frequently reducing
yields and delaying the ripening of fruit. Enrolamento or leafroll virus seems to be most acute in
dry years. The deep autumnal colours that are frequently admired by visitors to the Douro at
the end of the growing season are a manifestation of the problem. A co-ordinated programme
to eliminate viral diseases from the Douro’s vine stock is sorely needed.
At the opposite end of the scale from these microscopic pests and diseases are the
marauding wild boar that frequently venture into the vineyards eating grapes or tearing at
young vines. In a region where so much of the wildlife has been shot, poached or pilfered,
hunting wild boar is a sport that continues with understandable impunity.
Fertilisers anD herBiCiDes:
towarDs sustainaBle vitiCulture
Fertilisers are applied to correct the soil balance before planting, with the emphasis on
phosphorous, nitrogen, calcium, boron and organic material. Thereafter, most growers practise
a three- or four-year rotation, applying both organic and inorganic fertilisers. Thirty years ago
agrochemical salesmen worked hard in the Douro. Perhaps viewing fertilisers as a panacea for
low yields some growers (including some of the major shippers) undoubtedly over-fertilised
their vineyards in the 1980s, upsetting the vegetation balance to the detriment of their wines.
The use of herbicides has increased dramatically since the construction of patamares
in the 1970s and 1980s. Although weeds have to be hand-picked for the first two