Eric Webster, Schultz, Bruce | 4/19/2005 10:28:59 PM
CROWLEY – More than three dozen agricultural company representatives and county agents attended an LSU AgCenter clinic Friday (June 4) to learn more about how herbicides can drift from a field and affect other crops.
"When people ask me how far is safe, it’s hard to answer," said Dr. Eric Webster, LSU AgCenter weed scientist.
Even with no apparent surface winds, herbicides can drift far beyond the intended field and increase in concentration, he explained.
Webster showed the group different plots of rice at the LSU AgCenter’s Rice Research Station sprayed with varying concentrations of the herbicides Newpath, Roundup, Beyond and Liberty.
With calm winds at ground level, Webster said, cool air can be covered by warm air, causing the herbicide to be carried aloft and moved by above-ground breezes, eventually falling some distance from the intended field. The LSU AgCenter scientist said he recalled seeing the effects in Arkansas of Paraquat carried almost 10 miles.
Webster said as a herbicide drifts, the water evaporates, resulting in a higher concentration of chemical, so plants hit by drift far from the fields for which the herbicide was intended could show more damage than plants in closer fields.
In this study funded by the Louisiana Rice Research Board, some of the experimental plots at the rice station had been sprayed with lower amounts of herbicides at higher concentrations to represent the conditions that could render a crop worthless.
Webster said this year he has investigated several complaints involving the chemical Newpath, which is used in conjunction with herbicide-resistant Clearfield rice. The herbicide was applied aerially and then drifted to fields of nearby conventional rice.
The LSU AgCenter researcher said he expects such problems to continue with increased use of herbicide-resistant crops.
Each of the four chemicals – Newpath, Roundup, Beyond and Liberty – affects rice plants differently, Webster said, and he will be posting photographs on the LSU AgCenter Web site to show the differences.
Webster said steps can be taken to reduce or prevent drift, including:
–Avoid planting Clearfield immediately next to conventional rice.
–Cover fields of conventional rice with a flood just before spraying Newpath or Beyond, then drain the fields to normal levels.
–Apply herbicides with ground equipment for fields next to property with plants that could be damaged by drift.
–Use low-pressure nozzles and higher volumes of water when applying from the air.