What was it all about?

An extension of the industry’s initial Productivity, Irrigation, Pests and Soils (PIPS) orchard productivity program, this two-year project was tasked with developing the artificial spur extinction (ASE) technique as a crop-load management tool for the industry, including demonstrating its effectiveness and benefits compared to traditional chemical thinning, and providing information on the cost of implementation.

ASE involves selectively removing buds by hand to imitate natural bud extinction, and can be used to precisely determine where and how much fruit is set on each limb of a tree. The aim of ASE is to promote the vigour and performance of floral spurs, stimulate spur strength, and improve fruit quality and regularity of production.

The project team established two small plot trials where Gala and Fuji were used to compare ASE and chemical thinning for crop-load management. There was also a large semi-commercial-scale demonstration site to confirm results of the small-plot trials on a larger scale, and to enable accurate measurement of ASE labour requirements for a cost comparison between ASE and chemical thinning.

The team report that the research “has demonstrated clearly that ASE is a feasible tool for managing crop load without the need for chemical thinning”. In the project’s final report, they note that ASE produces higher yields and improves fruit quality, while giving growers the ability to determine the desired fruit number and placement on trees.

“Unlike chemical thinning, ASE provides a tool for precision crop-load management, enabling optimisation of bud position and improved light distribution within the canopy,” the report reads. “On top of these significant benefits, it simplifies the hand-thinning task, fruit maturity is more even, it is not weather dependent, and it removes the negative impact that most chemical thinners have on fruit size and shape.”

The researchers note that because the bulk of the thinning is completed prior to flowering, there is minimal resource wastage in ASE managed trees, hence fruit size is greater than in conventionally managed trees.

“There is also a positive response in fruit set of individual buds with the proportion of buds failing to set fruit being reduced and an increased proportion of buds setting multiple fruit. Return bloom is accentuated, reducing the risk of biennial bearing. Yields of 100 t/ha of high quality fruit are achievable,” the report reads.

The project’s cost comparison between ASE and chemical thinning suggests that ASE is also an economically viable approach to crop-load management. In the first year of implementation, ASE was found to be comparable in cost to conventional thinning, but in subsequent years proved more economical. This is because the first year of ASE is the most labour-intensive, requiring some tree restructuring and removal of buds across entire trees, but in subsequent years buds only need to be removed on new wood and pruning is reduced to the level normally required in the orchard.

The project also developed recommendations for industry, including the use of demonstration sites in major growing regions to train growers in the correct use of ASE. From these recommendations a concept has been entered to Hort Innovation, which at the time of writing was the apple and pear Strategic Investment Advisory Panel was set to provide advice on.

The implications for growers are that artificial spur extinction:

• Is a precision crop-load management tool that does not require additional chemical thinning
• Costs roughly the same as chemical thinning in the first year of implementation, but is cheaper thereafter
• Isn’t weather dependent
• Precisely spaces fruit for optimum light distribution
• Achieved more multiple fruit and a higher percentage fruit set than conventional trees in this research
• Produced up to 30 per cent higher fruit yield in Gala and Fuji, in a typical flowering season.

ACT NOW

Interested in giving ASE a go?

• Watch a video from the project demonstrating ASE here
• Download project fact sheet Chemical-free crop load management 
• Check out the project wrap-up article from the Feb/March 2018 edition of the levy-funded Australian Fruitgrower magazine