Dwarf apple trees are becoming more common in New Zealand due to their easier maintenance and more efficient production. However, this may increase the risk of spray drift if orchardists’ do not adjust spraying practices to match shorter dwarf varieties of fruit trees as compared with larger more traditional canopies as dwarf trees have less foliage to intercept spray. A study was carried out to examine the off-target movement of the spray plume from a conventional air-blast sprayer as compared with an experimental ultrasonic sensor sprayer in a dwarf apple canopy. The experimental sensor sprayer was set up to respond to the target canopy. Three treatments were carried out including a conventional Typhoon 1500 orchard sprayer, a single row ultrasonic sensor sprayer with either sensors ON or OFF. Each sprayer was set to deliver 500 L/ha of a 0.4 g/L concentration of a fluorescent dye (PTSA, 1,3,6,8-pyrenetetrasulfonic acid tetrasodium salt). The drift was quantified by using a series of mylar cards, petri dishes and fishing nylon. Results indicated a 24% decrease of deposited drift from 1 to 100 metres with the sensors turned on and a 5% increase with the sensors off as compared to the conventional sprayer
