A plant growth regulator (PGR) which targets increased fruit size and shape is helping Australian avocado producers yield high returns from their orchards in increasingly challenging farming times.

Sunny, a PGR from the Sumitomo Chemical Australia product line-up, has been used by Australian avocado growers to improve orchard productivity and fruit quality for more than 20 years.

Sumitomo regional manager south-east Queensland and Northern Rivers, NSW, Patrick Press said Sunny has two distinct effects. 

“It both increases fruit size and improves fruit shape and marketability. The larger the fruit, the better price per piece of fruit the grower receives. Sunny enables growers to get more of their fruit into the premium grade for which they are paid more,” Mr Press says.

“Growers aim for a tray pack-out of size 18-23 which attracts premium prices. The ideal size for the domestic market is 20-22 pieces of fruit per tray. 

“Sunny also results in rounder, less pear-shaped fruit as it helps fill out long necks, increasing overall fruit weight. Growers get better returns and consumers get more consistently sized fruit.

“As avocado trees are vigorous, excessive vegetative growth can limit fruit set and yield. Sunny limits what happens in the trees by stimulating hormones in the plant and redirecting energy into flowering and fruit rather than vegetative growth.”

Mr Press said August to September is the key time for growing regions from Bundaberg, Queensland and south to apply, although Sunny could be used on all varieties and in all growing regions throughout the year during flowering.

Best results were achieved in the market-dominant Hass variety due to its short flowering period, he said.

“As Sunny can be applied more than once a season, including when fruit is on the tree, this also makes it ideal for the Shephard variety which has two or three distinct flowerings and can be more susceptible to seasonal variables which impact fruit set.”

He says Sunny had no impact on trees if used year on year, unlike other alternatives which could have a detrimental effect from bio accumulation. 

Sunny also had a short 14-day withholding period unlike others that have a three-month prior to harvest restriction.

“Sunny is more expensive than other PGRs on the market, but in these tough times, growers are seeking increased profits to remain viable, and Sunny continues to pay dividends. 

“Overall total yield may improve in well-managed orchards.”

He said growers should apply Sunny as a foliar spray to healthy trees during flowering time – ideally mid bloom when 50 per cent of flowers had opened and in the early morning or late afternoon, in low wind and high humidity conditions. The spray is absorbed by soft tissues comprising leaves, stems and flowers.

Field trials conducted by Queensland’s Department of Agriculture and Fisheries, found Sunny had consistently increased average fruit size and improved pack-out performance compared with untreated controls.

Mr Press says despite challenging high production costs and oversupply concerns, growers should maintain good orchard management practices.

“They should maintain nutrition and watering and pick fruit, or trees won’t fruit next season,” he says.

According to peak industry body Avocados Australia, more than 800 Australian growers produce avocados year round for the premium domestic market and growing export market. 

Queensland produces nearly half of the crop.