Ethephon was tested for its ability to delay blossoming in 'Fantasia' nectarine (Prunus persica (L.) Batsch). The effect on harvest date was also examined. Ethephon, at 50, 200, and 400 mg/litre, was applied as a spray either on 5 April or on 25 April 1985. All sprays delayed the onset of blossoming. The delay in reaching full blossom (>90% open blossoms) was 6-15 days for the first spray, and 14-16 days for the second spray. Ethephon, at 200 mg/litre, significantly increased the number of open blossoms on tagged branches. In addition, all ethephon treatments improved initial fruit set; 200 and 400 mg/litre treatments were most effective. Crop yield (in a low-yielding season) was 8 x greater on trees which had received 200 mg/litre ethephon than on non-treated trees. The blossom delay did not result in slower fruit growth, and did not affect the date of harvest maturity
