Researchers in Australia are investigating the hormonal processes behind fruit drop in avocados, aiming to improve consistency and reduce crop losses. Unlike crops such as apples and grapes, avocados retain genetic traits of wild species, which makes the trees prioritise vegetative growth over fruit retention.
Dr Harley Smith, senior research scientist at CSIRO, said: "They're really genetically programmed for survival, not production. They put their energy into growing stems and leaves – not fruit." This results in immature fruit being shed during the growing season, with additional pressures from pests and climate variability.
Fruit drop has created problems for growers, with low-yield years proving as challenging as seasons with oversupply. In 2024, some North Queensland Shepard crops were not harvested due to poor market conditions. "There's nothing more heartbreaking than going into an orchard and seeing piles of avocados rotting because it would actually cost a grower more money to take the fruit to the market," Smith said.
Hormonal research
With funding from Hort Innovation and CSIRO, research has focused on the hormonal signals controlling fruit abscission. Auxin, which promotes fruit growth, and ethylene, which regulates abscission, have been identified as key factors. Results suggest that a drop in auxin activity initiates fruit loss, while ethylene triggers the separation of the fruit from the tree.
Trials are being conducted with plant growth regulators designed to sustain auxin or suppress ethylene. Sprays are being tested to deliver these compounds directly to fruit. Researchers are also evaluating whether combining these treatments with growth retardants to reduce vegetative flushes can create a balance between fruit and shoot development.
Smith noted: "That's where we believe future research must go – targeting the fruit and shoots simultaneously to create an equilibrium that a tree can sustain from year to year."
Industry impact
According to Avocados Australia, national production rose from 48,715 tons in 2013/14 to 150,913 tons in 2023/24. Export value grew from US$5.6 million to US$96.1 million in the same period. Hass remains the dominant variety, accounting for 82% of production in 2023/24.
CEO John Tyas said: "Production volatility results in market volatility, and that's not good for growers or consumers. Ideally, we would like to have a consistent supply all year round and year on year. Hopefully, the work being done with CSIRO will help us to achieve this."
Australia produces fresh avocados year-round due to regional diversity, from Queensland through to Western Australia. Research on hormonal regulation is expected to contribute to more stable yields and improved market predictability.
Source: Shepparton News
