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Technology provides tool to minimize spray drift

Few things a farmer can do to aggravate his neighbors can beat the rancor generated by pesticide spray drift.

Having a vulnerable crop wiped out by an ill timed or poorly applied pesticide tends to get one's dander up. And non-farm families take strong umbrage at prize camellias withering away from drifting herbicide injury.

And it need not happen, say Chuck Baker and James Blowers, agricultural spray industry spokesman on hand for the recent Agricultural Technology Conference on the Texas A&M-Commerce campus.

“Drift is a major issue for farmers and pesticide applicators,” said Baker, sales marketing manager for Delavan AgSpray Products, Lexington, Tennessee.

“But, with modern technology we can control pesticide spray drift.”

Baker said the key is observation. “Identify the conditions conducive to spray drift and manage them,” he said.

Conditions include droplet size, weather conditions, spray boom height, spray rig speed, and spray distribution.

“Small droplets, less than 154 microns, provide thorough coverage,” Baker said. “But small droplets are more prone to drift, evaporate quickly and do not penetrate the canopy easily.

“Medium droplets, 154 to 350 microns, provide good coverage, are less prone to drift and still offer good canopy coverage and penetration.

“Large droplets, more than 350 microns, are less prone to evaporation and drift but offer erratic canopy penetration. Leaf coverage may be reduced, especially with stem-type plants with few leaves.”

Weather conditions such as wind speed and direction, air temperature and humidity also affect drift. “Some wind may actually help prevent spray drift,” Baker said. “A little wind will reduce the potential for a temperature inversion, which can turn spray into a chemical fog that can drift for miles.”

Applicators can do nothing about weather conditions but they can manage spray discharge patterns by adjusting flow rates, droplet size, spray tip types and locations, boom height and operator speed.

“Pressure and flow rate determine droplet size,” Baker said. “And the higher the boom, the longer the droplet is suspended before it hits the target and the better chance it has to drift.

“If the boom is too low, coverage is less uniform and overlap is too great. Also, the faster the operator speed, the longer droplets are suspended. Speed creates more air turbulence as well.”

Baker says applicators should pay attention to wind speed and direction, air temperature, humidity, nozzle type and size, boom height, and spray rig speed.

“Also, follow the label. If applicators are good stewards, we'll have fewer regulations and fewer problems with spray drift.”

Blowers, Delavan account manager, said nozzle selection also plays a crucial role in spray drift control.

Nozzle selection depends on the type application, the material used, droplet size, coverage desired, and spray distribution. “Calibration is extremely important,” Blowers said.

“Delavan produces color coded droplet selection data charts from very fine to coarse to aid nozzle selection,” he said.

Blowers said the kind of nozzle — brass, stainless steel or plastic — influences wear and potential for drift.

“Nozzles can wear significantly, depending on composition and the product used. Abrasive materials, for instance, can wear brass nozzles rapidly. Stainless steel wears less rapidly and plastic less still.

“We have enough technology in nozzles, chemistry and spray application equipment to allow us to manage drift effectively,” Blowers said.

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