DPIRD and Hort Innovation Australia-funded research finds orchard thinning improves high-quality fruit yields

A three-year trial at a Manjimup commercial avocado farm has found strategic orchard pruning can lead to more consistent fruit quality. The research, funded by the Department of Primary Industries and Regional Development and Hort Innovation Australia through the Avocado Industry Capacity Building project, tested three different options for thinning, which were found to significantly reduce inconsistencies with avocados. DPIRD research scientist Declan McCauley said fruit thinning significantly reduced changes in avocado production from year to year. “Alternate bearing is a well-known phenomenon, whereby a carbohydrate imbalance in time causes large on-crops one year, followed by a small off-crop the following year,” he said. Mr McCauley said the orchard was thinned about a month after fruit began being produced at three different rates based on the number of fruits clustered on a stem. “Thinning was undertaken at rates of one, two and three fruits per (cluster) and compared with an unthinned control,” he said, “The results showed there were fewer trees with alternate and irregular bearing with the one fruit per (cluster) treatment — especially when compared to the control. “This resulted in more stable yields of avocados over the trial period.” Tree growth and mineral levels in the trees and fruit did not change with the different treatments, with the findings now being shared with the avocado industry both in WA and interstate. Other research undertaken through the project included an early disease detection technique being developed for producers. The process included dipping 20 fruit taken from an orchard a few weeks before harvest in tap water and leaving them on a tray in humid and warm conditions for up to two weeks to ripen. Mr McCauley said a manual dissection of the ripe fruit can then be used to measure the presence of disease for an upcoming harvest. “This outcome will eventually help growers make informed orchard management and marketing decisions to optimise orchard potential and profitability, as well as support supply consistency to secure export markets,” he said. The six-year project program is designed to support the development of the avocado industry in the State.