New calculator to minimise spray drift risk

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University of Queensland researcher Chris O'Donnell tests spray drift at the UQ wind tunnel.

PHOTO: Liz Wells

A calculator developed by University of Queensland researchers is helping to minimise the risk of spray drift from tank mixes, supplementing industry best practice guidelines and chemical labelling.

Called the Australian Ground Spray Calculator (AGSC), it became available late last year and now has more than 300 users Australia-wide.The AGSC requires users to select options from lists of variables such as nozzle type, droplet size and wind speed.

Lead researcher Dr Andrew Hewitt says the calculator is attracting particular interest from those using fungicides and insecticides, where smaller droplet size is often needed to ensure spray efficacy.

Dr Hewitt and his colleagues have been working with chemical companies, the Australian Pesticides and Veterinary Medicines Authority (APVMA), state agricultural departments and other research organisations to test different chemicals in a range of situations beyond those outlined on labels.

These results have gone into the algorithms behind the AGSC.

“It links with up to 20 years of work on droplet size and its effect on spray drift, and at the centre of it is testing we’ve done in a wind tunnel,” Dr Hewitt says.

The wind tunnel at the University of Queensland’s Gatton campus is one of only two in the world of its kind. Tests run in it have determined that coarse sprays can still include up to 13 per cent ‘fines’, which are more prone to drift. “This can reduce the efficacy of the spray and can also endanger neighbouring crops,” he says.

“Tank mixes can increase those fines considerably, and make the resulting spray behave differently to what is indicated on the nozzle catalogue data, which is always for water.”

Dr Hewitt says the use of one or more adjuvants in a tank mix could change the behaviour of droplets, as can atmospheric and spray equipment variables.

“Our hope is that the calculator helps to avoid drift to sensitive non-target areas by encouraging the use of sprays with zero fines, or by preventing fines from drifiting,” Dr Hewitt says.

Research into spray behaviour under variable conditions in both the wind tunnel and the field has been support by the GRDC through the National Working Party on Pesticide Application.

The calculator is available via email (below).

GRDC Research Codes UQ00060, UQ00072

More information:

Dr Andrew Hewitt,
0427 025 354

Chris O’Donnell,
0417 413 996,