Spray application technology

Abstract

Spray application technology on perennial tree crops has been a poorly researched subject. Many of the nozzles and sprayers were originally developed for use on row crops which have an even, flat profile and spraying is downward. Some of the short-comings of these systems were exposed when tree crops were sprayed, particularly the large and dense trees of 30 years ago.Much of the variation experienced in experimental results where fruit trees had been thinned with bioregulators is likely to have been due to application methods. Air-blast sprayers using hydraulic nozzles resulted in inconsistent results causing many research workers to revert to the use of hand lances and small pumps for their trials. Translation of these results to commercial practices then became a problem, as growers were reluctant to revert to the use of hand lances for thinning, particularly as orchards increased in size.The increased emphasis on reducing the use of chemicals, including bioregulators, on food and the need to use ecologically less wasteful methods of applying them has recently promoted more research into spraying techniques.Early work with spray technology identified factors causing variation. Such factors as the range and size of spray droplets, effect of climate, use of wetters, spreaders and stickers, the carrier medium (oil, water or combination), the use of propelled air, the crop species and it's configuration all impacted on the results.