Articles
Prediction of apple fruit thinning efficacy with a portable Vis/NIR spectrometer
Article number
1433_9
Pages
71 – 76
Language
English
Abstract
In apple fruit production early thinning is required to produce optimal yields, quality and to reduce alternate bearing.
However, the effectiveness of the thinning treatment varies each year.
The aim of the study was to predict fruit drop with a hand-held spectrometer after an early fruitlet thinning with plant growth regulators.
In 2023, at the Kompetenzzentrum Obstbau Bodensee (KOB) in southwestern Germany and the Laimburg Research Center (RCL) in South Tyrol, Italy, two apple cultivars (‘Gala’, ‘Braeburn’) received either no thinning or thinning sprays of 6-benzyladenine,
-naphthaleneacetic acid or metamitron between 8 and 15 mm (BBCH71). King and target lateral fruit were scanned before and after thinning with a visible/near-infrared device.
The green pigment ratios calculated from the reflectance in the wavelength of 693/674, (750-705)/(750+705) and the area between 699 and 939 nm showed excellent predictive results to separate fruit populations into persisting and dropping.
The receiver operating characteristic curves showed a fruit drop prediction accuracy (area under the curve) of >80% at three to five days after treatment for the RCL and KOB. At both locations, metamitron thinned well and showed the best prediction results possibly due to its mode of action as a photosynthesis inhibitor.
However, the effectiveness of the thinning treatment varies each year.
The aim of the study was to predict fruit drop with a hand-held spectrometer after an early fruitlet thinning with plant growth regulators.
In 2023, at the Kompetenzzentrum Obstbau Bodensee (KOB) in southwestern Germany and the Laimburg Research Center (RCL) in South Tyrol, Italy, two apple cultivars (‘Gala’, ‘Braeburn’) received either no thinning or thinning sprays of 6-benzyladenine,
-naphthaleneacetic acid or metamitron between 8 and 15 mm (BBCH71). King and target lateral fruit were scanned before and after thinning with a visible/near-infrared device.The green pigment ratios calculated from the reflectance in the wavelength of 693/674, (750-705)/(750+705) and the area between 699 and 939 nm showed excellent predictive results to separate fruit populations into persisting and dropping.
The receiver operating characteristic curves showed a fruit drop prediction accuracy (area under the curve) of >80% at three to five days after treatment for the RCL and KOB. At both locations, metamitron thinned well and showed the best prediction results possibly due to its mode of action as a photosynthesis inhibitor.
Authors
K. Biegert, S. Modugno, M. Peterlin, C. Andergassen, R.J. McCormick
Keywords
absorption, spectral index, receiver operating curves, plant growth regulators
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