Fungicide Application via Permanent Spraying System: An Effective Approach for Controlling Foliar Diseases in Apples

Apple powdery mildew, scab, and Alternaria fruit rot (AFR) are the most damaging diseases of apples worldwide, and their management relies on frequent fungicide sprays, typically applied with tractor-mounted airblast sprayers. This method is costly, labor intensive, and requires skilled operators. Spraying a hectare typically takes approximately one hour, which during critical periods may delay timely protection. Such limitations highlight the requirement for more efficient and sustainable spraying systems. We evaluated a permanent spraying system (PSS) equipped with Pulsar™ microsprinkler above the canopy. This system is relatively simple to install, inexpensive owing to its small diameter and lightweight delivery system, and is designed to deliver low doses of fungicides directly to the canopy. The PSS effectively controlled all three diseases under commercial orchard conditions, supporting its readiness for practical use. AFR was further reduced through microclimate manipulation that mitigated calyx cracking. Field trials conducted during six consecutive years (2020-2025) demonstrated that 5-10 min fungicide application reduced the incidence and severity of powdery mildew on leaves and scab on leaves and fruit by 90%-100%, and calyx rot caused by AFR on cv. Pink Lady by 70%-80% compared with untreated controls. Spraying water to cool down the fruits after fruit set further reduced calyx cracking and rot severity. Only a few applications were required, and disease control was comparable to, and in some trials greater than, that observed in the commercial grower treatment. PSS adoption may reduce pesticide inputs, production costs, soil compaction, and spray drift, and enhance precision in disease control.