Growth regulators on European pears : A thesis submitted in partial fulfilment of the requirements of the National Diploma of Horticulture of the Royal New Zealand Institure of Horticulture Incorporated

Abstract

There is no substitute in pear production for good husbandry practices. This is particularly so in producing Packhams Triumph pears which have an erratic cropping behaviour. However the productivity plant growth regulator paclobutrazol (PP333) can improve productivity of existing plantings and assist in the development improve of more efficient growing systems. A comparison of single foliar applications of PP333 (at 500 and 1000 ppm) with sequential foliar applications (at 500 ppm x 2 and 250 ppm x 4) and soil drench applications (at 1 gm a.i. and 4 gm a.i./tree) is made. In the season of application only sequential foliar applications suppressed or slowed down the rate of vegetative extension growth, though this was not a statistically significant result. Sequential foliar applications caused a significant (P<0.01) secondary flowering (return to bloom) response and also secondary fruit set. This response increases seriously the risk of fire blight (Erwinia amylovera) infection into these late blossoms. All PP333 treatments tended to increase yield, but soil drench applications increased crop yields significantly (P<0.05) , without reducing the vegetative vigor of the tree. Fruit quality, shape and size at harvest showed no abnormal side effects of PP333 applications, and long term storage quality remained unaffected.