Abstract
Ethephon (2-chloroethylphosphonic acid) was evaluated for its potential use as a flower thinner in several Japanese pear cultivars. In ‘Hosui’, ethephon at 100 or 250 ppm was applied to flower or fruit clusters 1 week before full bloom (WBFB) or 2 weeks after full bloom (WAFB). Ethephon treatment at 250 ppm at 1 WBFB resulted in a strong thinning effect. In ‘Kosui’, ethephon at 100-1,000 ppm was applied to flower or fruit clusters 2 or 1 WBFB, at full bloom (FB), or 2 WAFB. Ethephon treatments of 500 or 1,000 ppm at regardless of treatment timing showed a thinning effect. The thinning effect tended to increase when ethephon was applied at 1 WBFB. However, ethephon treatment of 1,000 ppm at 1 WBFB induced over-thinning. Ethephon treatments at 250 or 500 ppm at 2 WAFB decreased fruit weight at harvest. In ‘Wakahikari’, ‘Shinsei’ and ‘Niitaka’, ethephon at 250 or 500 ppm was applied to flower clusters at 1 WBFB. In these cultivars, fruit set was decreased when ethephon was applied at 500 ppm. It was concluded that ethephon treatment at 1 WBFB showed the thinning effect on ‘Kosui’, ‘Wakahikari’, ‘Shinsei’ and ‘Niitaka’ when applied at 500 ppm, and ‘Hosui’ when applied at 250 ppm. Thus, there seemed to be differences in the thinning effect of ethephon among the cultivars examined. The quality of fruits after these treatments was almost the same as that of control fruits.
