Kobus van Ierop copes with early summer problems in the vineyards

The vines are lush (too lush) and green (too green) … everywhere vineyard managers are running around trying to cope with all the growth this season.

What caused it? Lots of winter rain (more than usual), a cool spring, and cooler nights than usual for the time of year. We have not had any real heat yet – and the vines just love the conditions. Wet soils in early summer are good news for those in hotter areas without irrigation. In cooler climates, though, plentiful rain in spring caused excessive early growth that was, at places, then damaged badly by all the wind. 

More vigour early in a cooler season causes nutritional deficiencies in some cultivars – this show up in the leaves as yellow or brown spots. The soils of these vines are cool and the roots inactive, so the vine grows on its reserves and take what it needs from the leaves. Shiraz, for example, showed some browny yellow symptoms in the first leaves, as magnesium and other things are taken from them.

More vigour can also mean more rot and a denser leaf canopy – which can cause lower fertility for the year to follow. The buds bearing fruit for the following year need lots of sun the previous year for them to actually bear fruit and not only leaves or shoots. That is why we have to sucker – open up the canopy and remove excess shoots before flowering (which is the time when the buds are stimulated).

(On the other hand, why worry so much? I’ve seen photographs recently of bad hail damage to vines in the Robertson area.).

Flowering has just finished in most blocks and the grape berries are the size of small hard green peas. Some set beautifully and some not so well – meaning that only some of the flowers on the bunch formed berries, while the rest just fell off. That sometimes happen when you have wind or damp, cool, wet weather during flowering.

Green harvest

This is also the time of year when we start considering a ‘green harvest’. If the vine is still growing strongly, we wait. If the vine is showing signs of slowing down, we start removing bunches from weaker shoots. Genereally, depending on how much production we want (usually measured in tonnes of grapes per hectare), we will drop some of the crop – to sometimes as little as one bunch per shoot.

The best is for this to happen naturally: for the vine to grow a fairly good leaf canopy which stops growing two weeks before veraison (when the berries start softening and changing colour), and for the vine to bear a load of grapes that is in balance with the its own growth. Tipping, topping and green harvest are attempts by the vineyard workers to try and achieve what the vine should, ideally, do naturally.

And of course there are the animal problems. Snails, snout beetles, worms and krompokkels (a small kind of cricket) had a small feast again this year in some blocks. The trouble with using insecticides to kill them is that it also also kills the good goggas that feed on the mealy bug – which is our biggest problem in South Africa as it spreads leafroll virus.