Monday, August 18, 2008

Rust Mite - Q&A

Hi DJ's,

I am looking for some information on Rust Mite? What do you look for and how do you treat it? When is the timing of treatment?

Thanks,

Steve


We commonly ask growers these questions - 

Do you have poor early season growth?
Do you see rusty coloured leaves at harvest?

Chances are these symptoms are caused by Rust Mites. In wet spring conditions late bursting grape varieties can show poor spring growth symptoms commonly called ‘cold damage’ or restricted spring growth. Cabernet Sauvignon and Sauvignon Blanc are the major varieties that have a problem with poor early season growth.

Rust Mite bronzing on a leaf.

Poor growth symptoms show up as distorted leaves and uneven growth after budburst. This effect is worse when cold and wet weather occurs in Spring.

These symptoms are caused by the Rust Mites feeding on developing shoots and bunches during the early season.

After flowering, during late summer, these Rust Mites turn vine leaves bronze giving them the ‘rusty’ look.

A woolly bud wettable sulfur spray against rust mite is recommended if rusty or bronzed leaves were obvious in your vineyard in last Autumn after harvest.

How?

Wettable sulfur @ 500g/100lt (mite control label rate).

Check you ‘brand’ of Sulfur has mites on label.

Water rates of 600 – 900lt of water per hectare are recommended to ensure good coverage of the bark.

Growers have successfully used recirculating sprayers reduce waste.

Inclusion of Canola oil at 2% (2lt per 100lt) has been reported to improve control by up to 10-15%, but should only be applied if the variety being sprayed is fully dormant.

Spraying green vine tissue with oil has a risk of burning the developing shoot.

You should check your oil is GMO free.

When?

Rust Mites move on all varieties in response to temperature.

Chardonnay is the indicator variety for timing of spraying in each region. Chardonnay in the warmest part of McLaren Vale – the Sellicks Foothills are now at 10% Greentip (EL 4). Growers in the Barossa Valley are also approaching Greentip.

DJ’s feel the window for rust mite control in the Barossa Valley and McLaren Vale begins late this week – August 22nd and remains effective until the 4th of September. Growers in the Adelaide Hills, Clare Valley and Coonawarra will have a longer window.

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