Field deposit patterns of a diflubenzuron spray mix, after application to an apple orchard using an air‐blast sprayer; and a laboratory evaluation of physical properties and atomization characteristics

Abstract

Diflubenzuron (DFB) was applied to an apple orchard in Sodus, Wayne County, N.Y., USA, at the rate of 280 g active ingredient (AI) (or 1120 g of Dimilin® WP‐25) in 1430 L/ha, using an air‐blast sprayer’. Deposits were collected at ground level on target site and along downwind direction in the off‐target region, for assessment of droplet spectra and DFB content, before and after treatment. Physical properties, viz., viscosity at variable shear rates, surface tension, volatility and liquid‐atomization characteristics were also investigated for the spray mix under laboratory conditions.

About 39% of the applied amount was deposited at ground level of the treated region. Deposits on the off‐target areas decreased extremely rapidly with downwind distance; recovery was about 3% at 15.24 m but reached a level below the detection limit beyond 60 m from the treated area. Droplet frequency (no./cm²) values showed a corresponding decrease. The DFB content of the spray mix, prior to and after treatment showed levels within 7% from the theoretical value of 280 g AI in 1430 L. The data on physical properties and liquid‐atomization showed close similarity to those of water and were unlike those of a spray mix containing a “drift‐retardant” adjuvant.

Notes

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