Effect of Prohexadione-Calcium Dose Level on Shoot Growth and Fire Blight in Young Apple Trees

J. L. Norelli, S. S. Miller
2004 Plant Disease  
Norelli, J. L., and Miller, S. S. 2004. Effect of prohexadione-calcium dose level on shoot growth and fire blight in young apple trees. Plant Dis. 88:1099-1106. Prohexadione-calcium suppresses both shoot growth and fire blight in apple. In young apple orchards, there are conflicting requirements to control fire blight and allow sufficient tree growth for tree establishment. Application of prohexadione-calcium to various cultivars of orchardgrown apple trees ranging in age from newly planted to
more » ... ifth-leaf trees indicated that fewer highdose (125 or 250 mg·liter -1 ) applications of prohexadione-calcium provided a better balance between fire blight control and growth in young orchards than multiple low-dose (30 or 63 mg·liter -1 ) applications. The response of early-season shoot growth to prohexadione-calcium treatment dose was linear. However, trees that received high doses of prohexadione-calcium tended to grow more in the latter part of the season, resulting in little or no difference in total seasonal growth between trees that received a few high or multiple low doses of prohexadionecalcium. Enhancement of fire blight resistance by prohexadione-calcium was correlated with shoot growth suppression at the time of inoculation, and the resistance response to prohexadione-calcium treatment dose was linear. Fire blight management strategies that use prohexadione-calcium in young apple orchards are discussed.
doi:10.1094/pdis.2004.88.10.1099 fatcat:eyamln4ynjaljcbdx4h6bqmume