DJ’s are actively working on this issue. We are trialing no-sufur and minimal sulfur applications in vineyards to observe if by limiting sulfur use we limit Rust Mite symptoms in late summer.
The most common incidence of pest-flare that we see in the McLaren Vale Wine Region is a sudden build-up of Rust Mite (Calepitrimerus sp), which causes leaves to have a bronzed appearance. Vineyard scouting generally records the symptoms of bronzed leaves around the January 20, (CropWatch Vol. 17 Issue 26 - for example).
Rust mite leaf bronzing in a bio-dynamic vineyard. McLaren Vale Wine Region Vintage 2014.
Agrochemical use is often seen as a cause of Rust Mite pest flare. Conjecture has speculated that high rates of wettable sulfur may be responsible for interfering with predatory insects that naturally control Rust Mite.
Rust Mite symptoms are found in vines grown under minimal input regimes (above & below).
Close up picture of microscopic holes in leaves cause by Rust Mite feeding. Late Summer.
Note that in the McLaren Vale Wine Region, vines grown by different techniques including bio-dynamic, organic and conventional management show signs of bronzing. In biodynamic or organic vineyards (which don’t use Mancozeb or insecticides).
This anecdotal observation would support the theory that high rates of wettable sulphur, which we use for powdery mildew control, is a contributing factor to Rust Mite pest flare in late summer.