Fruit and vegetable growers and landscapers alike are recently being pressured by neighbors and legislators to reduce drift on their orchards, vineyards, and other horticultural operations. Pesticide costs continue to rise and growers need to improve application methods if they are to minimize costs to remain competitive and avoid prosecution under increasing environmental legislation. (Landers, 2002) Spray application technology research is necessary to improve spray deposition as well as reduce drift. Recent research suggests AI nozzles can reduce drift. Air inclusion nozzles produce droplets with a size or volume median diameter (VMD) of 450 μm. Cone nozzles on average have a VMD of 220 μm. Thus, AI nozzles by nature are less susceptible to drift. (Balsari, 2001)

However, biological efficacy trials are needed to understand if new delivery methods (i.e. AI nozzles) are suitable alternatives to conventional application technologies. while the potential for drift reduction using AI nozzles has been well researched, few trials have evaluated orchard air-blast AI nozzle pesticide efficacy, and fewer have studied plant growth regulator (PGR) efficacy under these regimes. Most recently, Cross et al. (2002) in England looked at the efficacy of fungicides and insecticides using three spray drift-reducing methods in orchards, where AI nozzles were one of the treatments. The British researchers found no consistent, statistically significant differences in the biological efficacy of the drift reducing treatments evaluated, as compared to conventional hollow cone nozzles. All treatments gave equal control of disease pests such as apple scab and powdery mildew, and insect pests like rosy apple aphid. Although the efficacy results of AI nozzles appear promising, more research is warranted.

The objective of the trial was to evaluate the biological efficacy of Prohexadine Calcium, (P-Ca, Apogee®, BASF Corp., Research Triangle Park, NC) a new plant growth regulator, on McIntosh apple, comparing two types of pesticide delivery systems: conventional hollow cone nozzle, and air-induction (AI) nozzles.