The US pollen tube growth model – first experiences in South Tyrol

The US pollen tube growth model (PTGM) to fine-tune blossom thinning for optimizing the timing of flower thinning was tested in South Tyrol for three years on two cultivars, namely ‘Gala’ and ‘Red Chief’ orchards located at different elevations.
The results pointed out that the thinning effects of ATS or a Lime-Sulfur mixture based on the PTGM did not generate significantly different thinning effects as compared to the standard thinning method and that counting must be done during a period where growers already have workload peak.
If it will be possible to automate the counting of open blossoms using camera systems, the method could certainly find a wider application.
Although the current PTGM did not offer positive results under South Tyrolean commercial conditions, the Fruit Physiology working group at Laimburg Research Centre continue refining instruments that could become a decision-making system to make the fruit thinning operation as safe and predictable as possible.

EUFRIN Fruit Thinning Working Group Symposium

C. Andergassen, D. Pichler, M. Peterlin, M.N. Smit, N. Hillmayr

chemical thinning methods, apple cultivar, PTGR method, altitude effect on thinning efficacy

https://doi.org/10.17660/ActaHortic.2025.1443.14