INTERACTION OF BENZYLADENINE AND NAPHTALENEACETIC ACID ON FRUIT SET, FRUIT SIZE AND CROP VALUE OF TWELVE APPLE CULTIVARS

In 2003 and 2004, we conducted field studies of the chemical thinning efficacy of the combination of Benzyladenine (BA) and Naphtaleneacetic acid (NAA) in comparison with NAA+carbaryl or BA+carbaryl sprays on 12 apple cultivars (‘Braeburn’, ‘Cortland’, ‘Delicious’, ‘Empire’, ‘Fuji’, ‘Gala’, ‘Gingergold’, ‘Jonagold’, ‘Jonamac’, ‘Liberty’, ‘McIntosh’ and ‘Sansa’). With most cultivars, the combination of BA+NAA gave good thinning and good increases in fruit size indicating that this treatment could be used as an alternative to combinations using carbaryl.
However, with ‘Delicious’ and ‘Fuji’ and to a lesser extent with ‘Braeburn’ the combination of BA+NAA caused many pygmy fruits to be retained on the trees.
The effect was strongest with ‘Fuji’ where more than 50% of the fruit on the tree were pygmies.
The effect appears to be primarily caused by NAA since NAA alone also gives pygmy fruit.
However, it is likely that the cytokinnin effect of BA which inhibits the complete formation of an abscission zone exacerbates the problem.
With ‘Empire’, the combination of BA+NAA was very successful and was much better than NAA+carbaryl which tends to cause stunting of fruit growth.
The BA+NAA combination would be an alternative with ‘Empire’ if carbaryl was removed from the market.
With most of the cultivars, crop value was enhanced considerably with thinning.
The greatest improvements were with BA+carbaryl, but BA+NAA also improved crop value.

X International Symposium on Plant Bioregulators in Fruit Production

T.L. Robinson

Malus × domestica, carbaryl, Sevin, Fruitone, Maxcel, chemical thinning, cropload, yield, fruit size, crop value, pygmy fruit

https://doi.org/10.17660/ActaHortic.2006.727.33