Spray drift on the radar

The possible effects of spray drift on health and ecosystems will finally be investigated more than a decade after a 2007 report raised concerns.

Marlborough District Council Land and Water team leader Peter Hamill said money in the 2020 budget had been earmarked for a spray drift monitoring programme.

The 2007 Environet report recommended monitoring the air quality near schools and residential areas in Blenheim.

‘‘The fact that agrichemicals can move into the atmosphere raises concern about the possible impacts on human health and aquatic and terrestrial ecosystems,’’ the report said.

Currently, spray drift is monitored on a complaints basis. From January 2016 to November 2018, 36 complaints were made to Marlborough District Council.

Since 2007, around 5000 hectares of grapes had been planted bringing the total area of vines to 26,000ha and the grape yield had more than doubled.

Past spray drift incidents have affected neighbours up to 30km away.

Hamill said it was not an ‘‘easy issue’’ to monitor spray drift.

‘‘We do have rules and a plan. There are best practice guidelines on when and the wind speeds [vineyards] should be sprayed.’’

Calculating spray drift was a complicated science and depended on many variables such as droplet size, angle of application, wind speed, temperature, humidity and the skill of the applicator.

The Environet report went on to say there had been very little investigation into the effects of agrichemical accumulation in the atmosphere.

Currently, the only measure of air quality in Blenheim was particulate size, which spiked during the winter because of fireplaces.

Sustainable Winegrowing New Zealand business manager Justine Tate said it had published guidelines to avoid spray drift.

‘‘The aim would be to avoid spray drift entirely but Marlborough is a pretty windy place. You have to get a spray on to protect your crop,’’ Tate said.

She said a lot of operators sprayed early in the morning, when there was less wind, to minimise drift.

The most common chemicals used on vineyards, sulphur, copper, potassium bicarbonate and glyphosate were generally considered of ‘‘low toxicity’’ to humans.

Tate said at this time of the year, most viticulturists were spraying sulphur. Sulphur, copper and potassium bicarbonate were used as fungicides to combat powdery mildew, botrytis and black mould.

Glyphosate was a herbicide used for killing weeds and was the active ingredient in Round Up. It had been linked to increased antibiotic resistance by Canterbury University scientists and recently a United States jury awarded terminally ill Dewayne Johnson US$289 million (NZ$440M) in damages, after it determined Monsanto’s Roundup