|Greene, George - PENN STATE UNIV|
|Norelli, John (jay)|
Submitted to: Plant Growth Regulator Society of America Meeting
Publication Type: Proceedings
Publication Acceptance Date: August 1, 2002
Publication Date: N/A
Technical Abstract: Excessive vegetative growth is a major problem for many apple (Malus x domestica) orchards in the United States. The plant growth regulator prohexadione-calcium (Phd-Ca) (Apogee), a gibberellin biosynthesis inhibitor, reduces 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 significant early growth suppression. The degree of growth suppression following foliar sprays of Phd-Ca differed among cultivars. By reducing vegetative growth Phd-Ca 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 Phd-Ca was used to control growth in 'Stayman' apple trees, fruit cracking increased. When Phd-Ca was mixed and applied with a calcium chloride spray, the growth cotrol activity of the Phd-Ca was reduced.