Cyber age way to manage weeds in wet paddocks

With soggy paddocks unable to accept a tractor carrying a boom sprayer, growers of rice, soybeans and tea tree turned to the latest technology - a drone capable of spraying three hectares an hour, at 40 litres/ha of chemical mixed with water.

The cost is currently three times that of a crop duster, but the footprint is much more contained, which counts where neighbours are concerned. More than that, growers speculated the cost of drone spraying was easily absorbed by extra yield at a time when these crops were demanding record prices.

Tea tree grower Rodney Rose, Codrington, fell victim to a "massive outbreak" of green caterpillar, or noctuid, which decimated new growth stressed by severe drought before Christmas and hampered by flooding rain soon after.

The outbreak was unprecedented in the history of tea tree growing on the Northern Rivers, which began to ramp up production in the early 1990s.

Growers with saturated paddocks faced difficulty in managing the outbreak using conventional spray equipment and some called in the pilots - both of aircraft, and now of drones.

Like a crop duster, a drone uses down force pressure to push spray into a crop; the difference being that a drone typically hovers 2m above a crop and spray drift is greatly minimised.

Drone pilot Scott Fisher, from Skytech Solutions at Lismore, applied Steward, usually used on soybeans to repress heliothis, followed by a second application of Lannate-L. Not all crops required the follow up spray.

"Around my plantation there are too many houses to be able to use a crop duster," said Mr Rose, who contracted Skytech to treat 150ha a the rate of 3ha/hr. "Using a drone to spray is nowhere near as risky.

"The tea trees were back in a flush of growth before I would have been able to get a tractor onto those paddocks."

While planes can get away with ultra low volumes of spray - 15l/ha - the drone needs twice that and Mr Fisher uses 40l/ha. A boom spray rig uses 100-150l/ha by comparison.