Submitted to: Plant Growth Regulator Society of America Meeting
Publication Type: Proceedings
Publication Acceptance Date: May 16, 2002
Publication Date: N/A
Technical Abstract: Excess vegetative growth is a major problem in many apple-growing regions, particularly in the eastern United States. Excessive shoot growth increases pruning time and pest levels, and lowers fruit quality. The plant bioregulator prohexadione-calcium (Apogee TM), a gibberellin biosynthesis inhibitor, reduced shoot growth when applied to apple trees. Beginning at petal fall (PF) to 10 days after PF a single spray or multiple low-dose sprays reduced shoot extension growth by 20% to 70%. Timing of the initial spray was more important than rate of application for early growth suppression. Apogee reduced pruning time in mature apple trees, enhanced spray penetration to the center of the tree canopy, reduced aphid populations and reduced the incidence of the shoot blight stage of fire blight. When Apogee was used to control growth in 'Stayman' apple trees, fruit cracking was increased. The multiple effects of Apogee on apple will be discussed.