The impact of off-target spray damage continues to affect the profitability of growers throughout many regions in Australia.

While cotton is the most visually effected by this spray damage in Queensland and New South Wales the impacts of off-target spray damage affects all production systems.

Grains Research and Development Corporation (GRDC) Grower Relations Manager North Richard Holzknecht said spray workshops had concentrated on reducing spray drift through better nozzle selection and better monitoring of weather conditions including Delta T and wind speed.

“However, spray damage caused by off-target movement of products in surface temperature inversions has emerged as the next issue for consideration,” he said.

“The damage caused by the movement of spray product by inversions impact people on a regional basis rather than neighbour to neighbour or on your own production system.”

Reducing the risk of spray damage both on farm and off should be a key focus of grain growers.

Recent spray application workshops have included information on the better identification of weather conditions that lead to the increased risk of spray damage due to movement in temperature inversions.

Spray specialist Bill Gordon from Nufarm said there were several steps growers and operators could take to minimise off-target movement of spray.

“Growers can control the when, where, how and what of spray application, the only thing they really can’t control is the weather,” Mr Gordon said.

“However, they do need to access reliable forecast information so they only apply products at times of lowest risk.”

To assist growers in improving spray practices the Grains Research and Development Corporation (GRDC) and the Cotton Research Development Corporation (CRDC) developed a Tips and Tactics GrowNote: Reducing Herbicide Damage.

This GrowNote explains the risk associated with a products volatility and potential for off-target spray damage; how environmental conditions and spray application setup influence the movement of all herbicides; and provides some alternative strategies to reliance on Group I herbicides.

5 steps to reducing off-target spray damage

1. Choose a product with low impact on off-target crop species

Product with lower impact on off-target crop species, different mode of action, lower volatile formulation and the adjuvant type used can all change the impact on off-target crops.

2. Follow the products label conditions

It is important to read the whole product label for guidance on application rate, spray quality, buffer (no-spray) zones and wind speed requirements

3. Select appropriate nozzles and spray quality parameters for the conditions

Select the coarsest spray quality that will provide an acceptable level of control for each product. Be prepared to increase application volumes when coarser spray qualities are used, or when the delta T value approaches 10 to 12.

4. Plan your spraying operation

Use weather forecasting information to plan the spray application. The Bureau of Meteorology (BOM) and forecasting websites can provide information on likely wind speed and direction for 5 to 7 days in advance. Pay attention to variations between predicted maximum and minimum temperatures above 5 to 7 degrees Celsius, delta T values below 2, low overnight wind speeds (less than 11 km/h) and predictions of dew or frost as these all indicate the likely presence of a surface inversion.

5. Continually monitor weather conditions during the spray application

When spraying it is important to monitor the weather conditions at the site of application. Always measure and record the wind speed, wind direction, temperature, relative humidity and herbicide and water rates at the start of spraying and at the end of every tank. Always expect surface temperature inversions will form later in the day as sunset approaches, and they are likely to persist overnight and beyond sunrise on many occasions. If the spray operator cannot determine that an inversion is not present, then no spraying should occur.

Mr Holzknecht said it was the responsibility of all growers to reduce the impact off-target spray damage has on their neighbours and regional farming communities.

He said failure to do so may see products deregistered or product use patterns further restricted.

More Information

Contact

Richard Holzknecht, GRDC Grower Relations Manager,
0408 773865, richard.holzknecht@grdc.com.au

Useful Resources

2017 Tips and Tactics: Reducing Herbicide Damage on the GRDC website.

Spray Application Manual on the GRDC website.