Tuesday 14 April 2009

Farmers in the Limestone Coast region planning on spraying for weed control this month are being asked to use chemicals responsibly and avoid spray drift.

PIRSA Rural Chemicals program manager John Kassebaum has urged landholders to follow all guidelines when using herbicides, and help reduce the risk of off-target damage.

“The Limestone Coast Region received enough rain in March to stimulate a good germination of weeds. Many farmers might now be spraying these weeds in preparation for sowing a crop, or for pasture manipulation,’ he said.

“The prospect of numerous people spraying at the same time compounds the risk of off-target damage unless everybody does the right thing, so we are asking people to take care, particularly if you are using 2,4-D in your herbicide mix for broadleaf weed control.”

Mr Kassebaum said all farmers should have the capability of measuring wind speed accurately using a hand-held weather recorder, such as a Kestrel instrument.

“Record the weather conditions before you start spraying and when you finish. Be alert for any changes in weather conditions while you are spraying and stop if necessary. Take records at intervals if you are spraying for more than a short period and keep a written record of your weather observations in a spray diary,” he said.

For 2,4-D products, he said it was also important to use low-drift or air induction nozzles to produce a spray quality in the required coarse or larger droplet range.

The use of high-volatile ester (HVE) formulations of 2,4-D is prohibited until the end of April. It is an offence to use these highly volatile products during the restricted period from 1 September to 30 April.

Generally, resellers no longer stock HVE formulations of 2,4-D because suitable alternatives are available, including low-volatile 2,4-D esters and 2,4-D amine. These products can be used throughout the year but care must be taken with their use.

“Low-volatile ester (LVE) formulations of 2,4-D can still move off-target through droplet or vapour drift if they are applied in unsuitable weather conditions, and 2,4-D amine can drift as droplets,” Mr Kassebaum said.

Until the end of April, the suggested minimum distance to susceptible crops such as grapevines – while using good chemical management to minimise drift and when consistent winds are blowing away from the area(s) of risk – is not less than 1 km for 2,4-D LVE and not less than 100 m for 2,4-D amine.

“If spraying 2,4-D LVE at night, take extra care to ensure that inversion conditions are not present. Use a smoke generator to determine wind direction and the presence of inversion conditions. Take note of the weather forecast for the next two days and do not spray 2,4-D LVE if the forecast is for hot and dry daytime conditions. 2,4-D LVE still presents some risk of vapour drift and this increases as temperatures rise and relative humidity falls,” Mr Kassebaum said.

All 2,4-D products now contain the following label directions.
DO NOT use unless wind speed is more than 3 km/hr and less than 15 km/hr as measured at the application site.
DO NOT apply with smaller than coarse to very coarse spray droplets according to the ASAE S572 definition for standard nozzles.