2017 ASHS Annual Conference

A novel, variable-rate, air-assisted sprayer was developed that applies pesticides based on real-time laser measurements of plant presence, size, and density. This sprayer has the potential to refine pesticide application, including minimizing off target waste, and greatly reducing negative environmental impacts. The objectives of this experiment were to evaluate (1) powdery mildew control and (2) drift and intentional spray applications to Cornus floridain the interior and exterior rows of a multi-row block from the newly developed laser-guided, variable-rate sprayer, referred to as the intelligent sprayer, and a conventional radial air-blast sprayer. Trees were monitored weekly throughout the growing season for powdery mildew severity. The most recently matured, fully expanded pair of leaves on the leader and two branches were ranked using a modified Horsfall-Barratt scale, and whole trees were rated on a 0-4 scale. Prior to each spray event, a set of water sensitive cards was placed back-to-back in predetermined trees. The cards in the area being sprayed were used to characterize intentional spray while those in the area not being sprayed were used to assess drift. Cards were analyzed for coverage (%) and droplet density (deposits/cm²). Plant height and caliper growth during the growing season were not affected by sprayer type. There was no effect of sprayer type on powdery mildew severity on the average of the three leaf pair ratings or overall tree rating. Position of the trees within the row affected the coverage but not droplet density. Intentional spray coverage was greater for trees on the edge. Percent coverage was lower for the intelligent sprayer than for the conventional sprayer. On each spray date, intentional droplet density was not affected by sprayer type. Direction the card faced did not affect percent coverage or droplet density from intentional spray. Coverage and droplet density on the drift cards were not affected by position of the tree in the row or direction the card faced. Drift coverage was not affected by sprayer type. There was a treatment x date interaction for droplet density on the drift card. The intelligent sprayer reduced spray volume by 56.1% compared to the conventional sprayer. The average per application cost for this trial was $3.99/2.4 acres for the intelligent sprayer and $8.14/2.4 acres for the conventional sprayer. Evaluation of the sprayer will continue, as will evaluation of a second generation retrofit sprayer.