Keep herbicides and other spray products on target.
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GRDC Grower Relations Manager – North, Richard Holzknecht, says while it is important that growers control fallow weeds early to maximise efficacy, it’s equally important spraying is only undertaken when weather conditions are right. Spray equipment also needs to be set up and operated appropriately.
“While spraying at night and in the morning is not restricted, product labels state that chemicals should not be applied when hazardous inversions are present,” Mr Holzknecht said.
He warned off-target damage could occur from physical drift and inversion drift, which posed a significant risk during summer spraying as day/night fluctuations in temperature often result in inversions forming overnight and or early in the morning.
“Wind speed, in particular, should be monitored at least every 15 to 20 minutes and if the wind drops, spraying should stop,” he said.
The main factors influencing drift potential were weather conditions at the time of spraying and how spray machinery was operated in terms of spray quality, speed and boom height. Photo GRDC
“So, planning and being proactive is extra important. Growers need to talk with their neighbours to determine the location of any sensitive crops, such as cotton, and ensure they understand label recommendations and permit regulations, particularly those governing the use of 2,4-D.”
Mr Holzknecht said the main factors influencing drift potential were weather conditions at the time of spraying and how spray machinery was operated in terms of spray quality, speed and boom height.
In an inversion, chemical droplets can remain suspended in concentrated form and be carried significant distances.
“It is important growers understand the weather conditions that indicate an inversion is present and avoid spraying during these times.
“Surface temperature inversions are often associated with calm, low wind conditions, dust remaining suspended, fog or mist forming in low areas and sounds travelling long distances. All these signs indicate the risk of inversion drift is significantly high.”
Mr Holzknecht advised growers and spray contractors to closely monitor weather conditions.
The Grains Research and Development Corporation (GRDC) is actively investing in spray application research and training to assist industry in implementing best-practice spray systems, and it recently released a new video explaining the key factors affecting spray drift.