Managing Vegetative Growth of Apples with Prohexadione Calcium can Influence Mid-season Spray Coverage

Abstract

Prohexadione calcium (BAS 125W or Apogee™) is a plant growth regulator being developed to control vegetative growth in apples. Prohexadione calcium acts within a plant by blocking the biosynthesis of growth-active gibberellin. The result is decreased cell elongation; thus, reduced shoot length. Applications of prohexadione calcium beginning when the apple trees have 2 to 15 cm of new shoot growth significantly reduce seasonal vegetative growth. Mid-season measurements of air blast spray coverage using water-sensitive cards show that trees previously treated with prohexadione calcium have greater spray coverage within the tree canopy than untreated trees. Hence, more efficient crop protection can be expected in apple trees treated with prohexadione calcium.