A new fruit thinning agent - Brevis - has passed its first season with flying colours offering a more flexible application window than currently available options.

Registered last August, Brevis contains the unique active ingredient metamitron - a non-hormonal agent that inhibits photosynthesis to induce fruit thinning.

Compared with currently-available fruit thinners, Brevis can be applied across a wider growth interval (8–16 mm central fruitlet diameter), a wider temperature range (10–25 degrees C) and as one or two applications to a maximum of 2.2 kg/ha per season.

According to Stuart Moncrieff, portfolio manager for plant growth regulators at ADAMA Australia, the new product has been successfully trialled by apple growers throughout all major growing regions in Australia.

“Secondary thinning is a vital management practice to optimise fruit set, yield and quality and to minimise biennial bearing,” Mr Moncrieff said.

“While apple growers have access to effective thinning technology these options are restricted by their relatively short application window or their suitability for use in modern orchard management programs.

“Brevis has a wider application window, no impact on beneficial insect species and can be used in most commonly grown cultivars in Australia which enables growers to vary the level of thinning according to their local climate and management.

“Likewise, it can be applied using existing spray equipment, it is rain-fast within two hours of application and it has no withholding periods so it has no impact on day-to-day orchard management.”

Trials conducted throughout Australia and overseas - supported by commercial experience of the past season - have shown Brevis delivers similar or better levels of fruit thinning as currently available options.

“Our field and technical staff worked with advisors and growers throughout the season to make sure they achieved optimum thinning results,” Mr Moncrieff said.

“Last season proved to be one of those ‘hard-to-thin’ years but most growers reported pleasing results.

Operations manager for MJ Hall and Sons in the Goulburn Valley, Sam Boyce, said he would incorporate Brevis into his thinning programs as a tool to maximise results.

“The benefits of this product are its capability to drop a larger amount of fruit than chemicals I’ve previously used,” Mr Boyce said.

“This is highly beneficial for me as I can reach my yield and size targets earlier in the season before hand thinning needs to occur.

“This year I hope to use Brevis on more Pink Lady and Gala varieties to further my knowledge and tailor it to fit my needs. I’m always looking to eliminate as much hand thinning cost as possible.

“I’m confident Brevis will help me achieve those results as we saw a significant decrease in the amount of money spent on hand thinning last season.”

Applied as a foliar spray, metamitron is absorbed primarily by leaves but does not translocate throughout the tree.

The rate of photosynthesis starts to decline within one hour of application and reaches its lowest point within three to five days of application.

Excess fruitlets stop growing and discolouration can be observed five days after application causing them to drop for several weeks after application.

Depending on application rate, timing and environmental conditions, the rate of photosynthesis returns to normal levels within two- to three-weeks.

The thinning effect provided by Brevis is dependent on radiation.

There will be a stronger thinning effect if cloudy conditions exist after application, in crops under netting or if night-time temperatures exceed 10 to 12 degrees C before or after application.

Brevis can be safely used in Granny Smith, Rubens, Red Delicious, Royal Gala, Pink Lady, Fuji and Envy apples.

Brevis was developed by one of the world’s leading crop protection companies, ADAMA.

“The fruit thinning properties of metamitron were first identified by researchers at the well-known Fruit Research Station in Jork, Germany,” Mr Moncrieff said.

“ADAMA then developed a formulation specifically for pome fruit thinning and continued development in collaboration with leading research institutes, advisors and growers throughout the world.

ADAMA is now focussed on the local roll-out of BreviSmart, a web-based decision-making tool that utilises local weather observations and forecasts to provide ‘real time’ recommendations for the best application window.

“BreviSmart has been in global development since 2013 and we are confident of providing this service to support Australian growers and their advisors within the next season or two,” Mr Moncrieff said.

“The best use of Brevis will always rely on the local knowledge of growers and their advisors but this tool will provide added confidence in determining the optimum window for application.”