CONTROL OF RUSSETING OF GOLDEN DELICIOUS APPLES BY GROWTH REGULATOR TREATMENTS

T. Eccher
Tests were carried out in 1980 and in 1981 in two different localities spraying GA4+7 or a commercial formulation containing GA4+7 and BA on half - trees of Golden Delicious, leaving as check for each tree the untreated half. In 1980 both products were sprayed at 50 ppm of GA4+7 in four weekly applications, the first spraying being applied at the beginning of bloom or 1, 2 or 3 weeks later. In 1981 only GA4+7 was tested at 6, 12 and 24 ppm.

At harvest, the apples on the treated half-plants were picked separately from those on the untreated half; each apple was graded for russeting, and longitudinal and transversal diameters were measured.

The russet percentage of each treated fruit was then calculated as compared with the average russet score of untreated fruits from the same tree.

In the locality where check fruits showed slight incidence of russet, the average russet score of treated fruits was halved as compared with that of the check fruits; in the orchard where russet was heavy on check fruits, russet of treated fruits was about 30 % of the check. Late sprays proved less effective than early ones.

Growth regulator treatments also altered significantly the shape of the fruits which were elongated. GA4+7 treated apples were rather conic while fruits treated with GA4+7 plus BA were oblonged, ribbed and sometimes truncate.

In 1980 growth regulator treatments also severely affected the differentiation of flower buds reducing their number to 35 % compared to the control.

However the concentration employed in these trials were quite high. On the contrary, the low concentrations of GA4+7 used in 1981 prevented russet without reduction of flower buds.

Eccher, T. (1983). CONTROL OF RUSSETING OF GOLDEN DELICIOUS APPLES BY GROWTH REGULATOR TREATMENTS. Acta Hortic. 137, 375-382
DOI: 10.17660/ActaHortic.1983.137.44
https://doi.org/10.17660/ActaHortic.1983.137.44

Acta Horticulturae