A comparison of spinning disc atomisers and flat fan pressure nozzles in terms of pesticide deposition and biological efficacy within cereal crops.

Abstract

The deposition of spray applied through hydraulic flat fan pressure nozzles mounted on an Oxford precision sprayer and spinning disc Micromax atomisers were compared in wheat crops at a range of growth stages. The Micromax rotary atomisers when operating at a disc speed of 5000 r.p,m. (drop size VMD 80-90 µm) were found to be the most efficient at all the growth stages examined. The Micromax atomisers operating at 3500 r.p.m. disc speed (drop size VMD 130-140 µm) produced a similar spray deposition pattern to the flat fan nozzle although crop and ground deposits were lower up to GS59 with the Micromax atomisers. The pest control efficacy of the two nozzle types was evaluated in three aphicide trials on wheat crops. In the first two trials deltamethrin at one twentieth of the recommended dosage rate (6.25 g a.i. I^-1) provided a similar degree of cereal aphid control to the applications at half the recommended dosage rate using both types of nozzle. In the third trial similar levels of aphid control were achieved using deltamethrin at one quarter of the recommended dosage rate applied using the rotary atomisers compared with one half of the recommended dosage rate using the flat fan nozzle. The impact of the deposition patterns on beneficial insects is discussed.