FRUIT QUALITY AND CROPPING OF PEARS I. RESPONSES TO CHLORETHEPHON, NAA AND HAND THINNING.

In the 1989/90 season six-year old ‘Nijisseiki’ and ‘Hosui’ Asian pears trees were part-tree thinned with either chlorethephon (400 ppm applied 15 DAFB) or by hand (leaving one fruitlet at each fruiting site eight weeks after full bloom) in a split plot design with chlorethephon as the main plot and hand thinning as the sub plot.
Chlorethephon reduced fruit set of ‘Nijisseiki’ and ‘Hosui’ Asian pears by 34 percent and 18 percent respectively.
In a seperate experiment whole-tree sprays of chlorethephon (400 ppm applied 15 DAFB) increased fruit fruit set of ‘Comice’ European pears by 51 percent.
Chlorethepon removed one ‘Nijisseiki’ fruitlet per cluster compared to unsprayed controls.
Mean fruit weight of ‘Hosui’ at harvest was reduced by 16 percent due to chlorethephon however, there was no effect of chlorethephon on mean fruit weight of ‘Nijisseiki’. Hand thinning of non-sprayed plots in the part-tree experiment significantly increased mean fruit size of ‘Nijisseiki’ at harvest.
When hand thinning followed chemical thinning however there was no increase in mean fruit size compared to unsprayed controls for this cultivar.
Chlorethephon and hand thinning each increased return bloom of ‘Nijisseiki’ and their combined effects on return bloom were additive.
In a third experiment 400 ppm chlorethephon increased the incidence and severity of flesh spot decay after 12 weeks storage at 4°C. NAA had no effect on fruit set or mean fruit weight of ‘Nijisseiki’ but reduced flesh firmness at harvest and after storage by 6 percent and 7 percent respectively.

VII International Symposium on Plant Growth Regulators in Fruit Production

Steven J. McArtney, G. H. Wells

https://doi.org/10.17660/ActaHortic.1993.329.56