2017 ASHS Annual Conference

Tree fruit production could not exist as it does without the temporary introduction of pollinators (predominantly Apis mellifera) and utilization of pollinizer trees dispersed orchard-wide. Despite the importance of pollination, tree fruit growers continue to utilize this archaic pollinator + pollinizer system. Facing global decline in pollinator species, climate change, and the myriad perennial challenges growers face with the pollinator + pollinizer model, we are investigating alternative, precision pollination systems. This presentation describes our vision for productive orchard systems in the absence of both insect pollinators and pollinizers, and results of field trials with our precision pollination system utilizing liquid pollen suspensions applied with electrostatic sprayer technology. In 2014, supplemental pollination with a single application of pollen (ca. 37 g/ha) improved ‘Tieton’ sweet cherry (Prunus avium L.) fruit set by 15% compared to open-pollinated limbs. Pollen density on the stigmatic surfaces of treated flowers was nearly double the density on open-pollinated flowers. Analyses of pollen density on the stigma revealed pollen deposition on flowers in all positions (i.e., on both the ‘front’ and ‘back’ of the limb) from a single pass in the field. Fruit yield was similar for open-pollinated trees and those treated with two applications (at ca. 50% and 100% full bloom) of pollen suspensions through bee-exclusion netting deployed prior to flowering (i.e., in the absence of natural pollinators). In 2015, field trials in several sweet cherry cultivars revealed improvements in fruit set (+12 – 45%) from both single and double applications of supplemental pollination at both 37 and 74 g/ha pollen. These results suggest that artificial, precision pollination systems are effective for either supplemental or replacement pollination. Our research continues to investigate effects of application timing and pollen rate as well as the use of sensor technologies for targeted application.