Tuesday, October 25, 2011

Downy Mildew Oilspots - UPDATE 25/10/2011

Above- A downy mildew primary oilspot.

Above - A secondary fresh downy mildew oilspot on a Grenache leaf.

Wednesday, October 12, 2011

Powdery Mildew - Identification photos.

Sam Freeman shows the underside (below) and top side (right) of powdery mildew found in Cabernet Sauvignon. Powdery mildew increases during spring from a small amount and spreads.

Fresh powdery has the appearance of a whitish film on the backs of leaves. New leaf growth is distorted and older leaves become blackened.

Powdery mildew spores are carried by air and, once active, will continue to spread in dry conditions.

Monday, October 10, 2011

Eutypa Dieback - Spring Identification Pictures.

Eutypa and other trunk diseases have been identified as causing significant problems in South Australian vineyards. This season appears to be a 'big' year for Eutypa symptoms.

Eutypa is present in many vineyards- of all ages. The fungus grows slowly in the wood and produces foliar symptoms several years after the initial infection. Pictured below is a 10 year old vineyard in the Sellicks Foothills demonstrating that Eutypa can be found in 'young' vines.

Eutypa dieback foliar symptoms are are most obvious in spring when shoots are 30-70 cm long.

Eutypa infection reduces bunch numbers and reduces vine yield.

Thursday, October 6, 2011

Shoot thinning in Shiraz

Before thinning.
Note the before (above) and after (below) photos of shoot thinning in Shiraz.

Post thinning.
Being more attentive about vine balance and aggressive shoot thinning, in pinot and shiraz, aims to reduce crop loads and shoot numbers. It is an interesting technique for increase light exposure inside vine canopies.

The following shoots are thinned:

- absolutely all water shoots.

- any other infertile shoots without visible inflorescences, which emerge from the pruned spur. However, at least one near-stem new shoot must remain at each shoot position for the following winter pruning.

- if there are two or several shoots growing from one bud, the strongest one (with inflorescences) is retained, all others are removed. Many varieties have a tendency to produce several shoots from each shoot position.

Shoot thinning is carried out when the new shoots have reached a length of approx. 10 to 30cm, ie at a time in spring when the whole vine is still easily manageable.

Tuesday, October 4, 2011

Leaf Botrytis - UPDATE 4/10/2011

Leaf botrytis.
In long periods of wet weather, botrytis can infect the dead and dying parts of young stems, and leaves damaged by wind and hail. The resulting leaf symptoms can have a brown colour.

The appearance of leaf and stem botrytis doesn't mean that we will get botrytis at harvest, but it does show that recent weather is conductive to it.