RESPONSE OF ‘VICTORIA’ PLUMS TO CHEMICAL BLOOM THINNING

During the period 1998-2000, thinning trials were conducted using bloom thinners on mature European plum trees at Ullensvang Research Centre in western Norway.
In 1998, unsprayed control and hand-thinned ‘Victoria’ trees were compared with trees treated at full bloom with a single application of 1% Armothin^® or 1.5% ammoniumthiosulphate (ATS). The same program was conducted in the following two years with the addition of a single full bloom treatment with 250 ppm ethephon and a post-bloom application one month after full bloom with the mixture 10 ppm 1-napththaleneacetic acid (NAA) and 75 ppm ethephon.
Generally, thinning treatments reduced crop load and enhanced fruit quality (fruit size, soluble solid content, fruit firmness and ground and surface colour), but the results varied from year to year.
Fruit set was reduced to about half of control values and the percentage of class 1 fruits was doubled compared to the control trees.
All thinning compounds caused some minor leaf injury but no fruit damage.
No differences in the amount of gummosis (internal disorder of the fruits) were observed due to treatments.
Return bloom was improved by thinning.

XXVI International Horticultural Congress: Key Processes in the Growth and Cropping of Deciduous Fruit and Nut Trees

M. Meland

Prunus domestica L., fruit density, yield, yield efficiency, fruit quality, return bloom, thinning

https://doi.org/10.17660/ActaHortic.2004.636.33