Advancing artificial pollination systems in sweet cherry

Katherine  Chattin Taylor

doi:10.7273/000003976

Sweet cherry (Prunus avium L.) is an economically important tree fruit crop for the United States, with 60 - 70% of fresh-market production occurring in Washington. Production depends upon commercially managed pollinators (Apis mellifera) for annual pollination. Declining pollinator populations worldwide is a risk to sweet cherry production and all entomophilous cropping systems. Sweet cherry fruit set is perennially unpredictable and highly variable among genotypes. The objectives of this research project are: (1) Determine the effect of supplemental spray pollination in commercial sweet cherry orchards using various pollen rates and application technologies (15 - 60 g pollen/acre; electrostatic and airblast application); (2) Develop a method to measure viability of pollen throughout commercial application; and (3) Investigate variability in pollen germination among sweet cherry cultivars and growing seasons - 10 cultivars ('Benton', 'Bing', 'Chelan, 'Lapins', 'Santina', 'Selah', 'Skeena', 'Sweetheart', 'Van', and 'Ulster') and two growing seasons. In the first experiment, fruit set, yield, and fruit quality were collected from field trials (four of 'Chelan', one of 'Benton', and one of 'Skeena') conducted in eastern Washington during 2018 and 2019 to measure rate efficacy of supplemental spray pollination. In the second and third experiments, pollen germination analysis on agar medium was used to determine viability. In 2018, I recorded a 5-fold variation in 'Chelan' fruit set, ranging 9% to 46%. In 2019 'Benton', 'Skeena', and young 'Chelan', pollen-treated blocks exhibited fruit set increases compared to untreated controls (P <0.30). Less yield variability was observed among 'Benton' pollen-treated blocks (7%) compared to untreated control (35%). A general lack of significant effect on fruit set may suggest natural pollination was nearly maximized in field trials. Of three methods tested, results of 'hand-held' and 'tree-plate' spray collections demonstrated that pollen in suspension maintained viability for up to 90 mins during electrostatic spray application. Pollen germination rates varied among cultivars in 2019 and between growing seasons in half the cultivars (P <0.05). Artificial pollination systems can increase sweet cherry fruit set when pollination is a limiting factor. Trends in pollen variability among cultivars can be utilized for pollinizer selections and pollen-production for artificial application systems.

Advancing artificial pollination systems in sweet cherry

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