Many of today’s most grown apple varieties need fruit thinning to obtain the right fruit bearing, desired fruit size, and to avoid biennial bearing.

Hand thinning is very costly and normally takes place after natural fruit drop, Fine Agrochemicals marketing director, Wim Aelbrecht.

“Hand thinning usually happens too late to break biennial bearing as fruitlets start suppressing flower initiation between four to six weeks after full bloom, depending on the variety.

“A reliable thinning program depends on chemical fruit thinning around and after bloom. This will give a substantial labour saving and is the best guarantee to prevent biennial bearing patterns,” Mr Aelbrecht said.

“Even with the range of products available today, thinning is not as straightforward as you might think. Weather conditions, tree vigour, rootstock, flower stage or fruitlet growth stage all play a role to what extend the treatments are effective. There is no miracle solution!”

Exilis saves substantial labour and can prevent biennial bearing patterns.

Exilis 5XL

Mr Aelbrecht said one of the main available tools is Exilis 5XL, based on 6-BA. Containing 100 g/l 6-BA, this patented SC formulation is highly concentrated and yet is classified as non-dangerous goods.

“Exilis 5XL has excellent solubility, is easy to measure, and has a favourable low dose rate. Exilis 5XL comes from Fine Agrochemicals, the same UK producer for Easyfresh (post-harvest freshness), Perlan (typiness/elongation and russet control) and Corto (vegetative growth control).”

6-BA

6-BA, or 6-benzyladenine, is the well-known cytokinin for optimum post-bloom thinning in apples.

Mr Aelbrecht said 6-BA is readily taken up in the leaves and translocated within the plant tissue. 6-BA stimulates the first natural fruit drop after petal fall and stimulates flower initiation for the next year.

“Furthermore, 6-BA is also up taken by the young fruitlets and promotes cell division in those important first weeks after which cell division ceases. Final fruit size is greatly influenced by the total number of cells, so 6-BA can give bigger fruit size. This positive effect is supported by numerous trials all over the world,” Mr Aelbrecht said.

Recommended program

“Exilis 5XL is a secondary thinner designed for use on apple trees in a program together with other thinning products like, NAA, ATS, etc,” Mr Aelbrecht said.

“Optimal application timing is at king fruit size 10 to 12 mm, but most important: apply with temperatures above 18°–20°C for some days, mainly after treatment.”

Fine Agrochemicals is a UK based company and focuses on the development, manufacture, and marketing of plant growth regulators (PGRs) for fruit, flower and broadacre crops.

In Australia, Fine Agrochemicals distributes its fruit PGR portfolio in partnership with Elders.