美国 Clemson 大学的研究者,进行了30多年的桃疏除剂的研究,试用了100多种药剂,仅有疏花剂 NPA 和疏果剂3CPA 两种得到了环境保护机构的许可。到七十年代初,这两种疏除剂因在美国某些地区表现不良而停止生产。以后又用乙烯利试验了多年,也因在美国北部某些地区发生药害而停止使用。1974年,又一种 Researchers at Clemson University in the United States conducted research on peach sprouts for over 30 years and tested more than 100 kinds of medicaments. Only the flower-thinner NPA and the fruit-thinner 3CPA were approved by the environmental protection agency. By the early 1970s, these two types of sparse drugs stopped production because of poor performance in some parts of the United States. He later experimented with ethephon for many years, and stopped using it because of phytotoxicity in some parts of the northern United States. In 1974, another one