Spray drift warning for chemical users

NSW Department of Primary Industries has issued a timely reminder for growers, agronomists and spray applicators to carefully plan their spray operations to prevent herbicide damage to nearby crops.

Off target movement of hormone based herbicides as well as glyphosate has caused significant damage to summer crops in the North-West of the State during the last three seasons.

Now, as growers seek to control the weed burden following the recent rains, reports are already coming in of damage to some crops. Crops most at risk are sorghum, sunflowers, mungbeans, and cotton.

District Agronomist for Moree East, Stephanie Belfield, said while growers are under pressure to control weeds, they have a responsibility to prevent spray from drifting onto adjoining crops and pastures.

‘2,4-D herbicides are valuable and effective products for weed controls in fallows and pastures under the right weather conditions; however, it is essential that potential impacts on nearby sensitive crops are considered,’ Ms Belfield said.

‘Esters of 2,4-D are particularly risky to use in regions where sensitive crops are grown due to their volatility and if other effective options are available they should be used instead.’

Cotton Industry Development Officer at Moree, Julie O’Halloran, said that, in addition to 2,4-D based products, glyphosate herbicides were also a potential concern to this year’s cotton crops.

‘About 75 per cent of the cotton in the Gwydir Valley is Roundup Ready®, however these varieties are only tolerant to glyphosate at the very early seedling stage,’ she said.

‘Drift of glyphosate onto these crops after the four leaf stage can significantly impact on yield.’

New label requirements on the use of herbicides with 2,4-D as their active ingredient that came into effect on November 30 limit application to coarse to very coarse spray droplets and within wind speeds of 3 to 15 kph.

Growers should check nozzle manufacturer’s specifications for the nozzles they are using to ensure they meet the new requirement, according to Narrabri-based DPI district agronomist, Tracey Farrell.

‘The standard flat fan and drift guard types of nozzles are generally not suitable for producing coarse and very coarse droplets,’ Ms Farrell said.

‘It is also important to remember that while low drift nozzles reduce the number of 'driftable' droplets and therefore reduce risk, they are not a guarantee that a product will not drift if application set up and conditions are unsuitable.’

All pesticides will drift if the meteorological conditions and/or application set-up are unsuitable. Non-volatile formulations can drift as far as volatile formulations under inappropriate weather conditions such as low humidity, high winds, and inversion conditions.

Temperatures above 28 degrees and low humidity increase evaporation rates, droplets quickly lose size and mass, increasing drift risk. Under these conditions, up to 40 per cent of the herbicide does not reach the intended target.

Further information can be obtained from DPI’s Moree office on 02 6752 5111 or Narrabri office on 02 6799 1548.

Media contact: Annette Cross, NSW DPI Tamworth, on 02 6763 1243 or 0427 201 840.