MEASUREMENTS OF FOLIAL AND GROUND DEPOSITS IN FORESTRY AERIAL SPRAYING

Forestry aerial spraying is done to control defoliation by insects. In this work the deposition and off-target drift of sprayed material wer e studied under different atmospheric conditions. Field trials were ca rried out in 1984 and 1986 with Grumman TBM Avenger and Cessna C-188 A gTruck sprayer aircraft using hydraulic spray nozzles (D((v.5) -75 mum , generated spray) and Micronair atomizers (D(v.5) - 55 mum, generated spray), respectively, at a forest site near Dunphy, New Brunswick, Ca nada. The stand consisted of jack pine (492 stems/ha with average heig ht 11 cm) and black spruce (1304 stems/ha with average height 5.1 m). From 60 to 115% of the emitted mass was accounted for in combined depo sit and drift measurements for individual spray applications. This wor k concentrates on deposits on foliage and ground deposits. For aircraf t heights varying from 32 to 63 m above ground (constant for a specifi c trial), total integrated deposits varied from 47 to 50% of emitted m ass (non-volatile component) for the range from spray line to 400 m do wnwind. The average total deposit to 910 m was 34% of emitted mass for the TBM and 29% for the C-188. Atmospheric conditions varied from sta ble to slightly unstable. We were unable to do a systematic combinatio n of aircraft weight, wind speed and direction, relative humidity, and atmospheric stability. However a multi-variable regression analysis w as made and showed a significant relationship between total deposit an d aircraft height.