Concentrated, low-volume aerial sprays to improve spray distribution in large avocado trees
The avocado industry has comprehensive guidelines for ground-based spray application to avocado orchards, but there are no current guidelines for aerial spray applications. Helicopter-applied deposits from a dilute spray application (600 litres/ha) of copper on a commercial Hass avocado orchard (12 m tall trees) were compared with twotimes (300 litres/ha) and three-times (200 litres/ha) concentrate sprays with addition of varying rates of the superspreader adjuvant, Du-Wett®. Tartrazine dye was included as a deposit tracer. Concentrate sprays, with adjuvant addition, consistently gave higher spray deposits on difficult-to-wet fruit than the dilute aerial spray. Deposits on fruit in all canopy zones were increased with concentrate sprays, but particularly in the upper, lower and outer canopy zones. On foliage, concentrate sprays with adjuvant addition gave similar spray deposits to the dilute spray. Leaves in mid and inner canopy zones tended to be less well targeted by concentrate sprays. This must be considered if targeting dense trees with aerial sprays.