In all cases Bordeaux vineyard owners believe that 2014 will be a solid year regarding quality – the stories differ however regarding volume. In our previous post “The 2014 Bordeaux Harvest is Underway” we reported on the weather influences this year. As always in agriculture weather is one of the most significant influences when reviewing a crop from any given year.
The Bordeaux 2014 vintage has seen a phenomenon that has left owners looking at some of their grapes shrunken and deflated. There appears to be a handful of reasons. Some have spoken about a Japanese insect called “Drosophilia Suzukii.” This Asian bug that arrived in the region within the last 5 years, bites the grape berry and sucks small quantities of the flesh of the fruit. The problem comes as a result of the breach in the skin. With the skin seal broken oxygen oxidizes the grape and in effect turns it to vinegar. The solution for the bug is to spray with sulphites and since this is a widespread practice for Bordeaux vineyards this bug is the least likely reason for reduced volumes this year.
The most likely reason is as a result of the timing of the rain and sun/heat in the latter part of the growing season. The resulting shrinking and wilting looks like a bit like Botrytis at first look but in fact it is as a result of two possible causes.
1. The first is that the vines are growing on soil that drains very quickly. Sandy and gravelly soils allow water to pass through and drain in contrast to chalk and clay soils which act more like a sponge – retaining water for longer. For vines that are on sandy or gravel soils if the vineyard is trying to cope with a wet august followed by a hot dry September (as we had this year) then the plant goes into a state of shock as it seeks magnesium from the water that would be carried in the water. The scarcity of water and its soluble magnesium causes the fruit to grab what it needs in a short term panic from the stem/stalk of the bunch of grapes. This in turn weakens the stem and has the effect of strangling the fruit leaving it partially or in some cases fully shrunken and wilted. The effect is a 10% to 15% reduction in volume of fruit.
2. The second possibility is that the vines are on soils that do not drain so readily and therefore have better access to magnesium and water through a dry patch. Why then are we seeing some vineyards with shrunken wilting fruit when they are blessed with soils that don’t filter the water so quickly? In this case it is because the vineyard owner is looking to maximize fruit volumes. Many of the more well-known brands and appellations conduct what is known as the “vendange verte” or green harvest. The green harvest is the practice of removing several bunches of grapes to increase the concentration of flavours for the remaining bunches. This has the effect of reducing the number of grapes seeking magnesium and in turn keeps the grapes looking healthy and strong. If however, the vineyard owner chooses not to do a vendange verte – most likely because their price per bottle sales are not sufficient to support the reduced volumes from the harvest – then the balance of water/magnesium to fruit will be unsustainable and the grower is left with the same problem as No.1 above.