Immediate and residual effects of prohexadione-calcium, with or without ethephon, applied in a low-pH solution on vegetative and reproductive growth in sweet cherry trees (Prunus avium L.)

Abstract

SummaryA single application of either prohexadione-calcium (Ca) at 250 mg l–1, or of prohexadione-Ca at 250 mg l–1 plus ethephon at 180 mg l–1, dissolved in water acidified with 1.0 g l–1 citric acid was applied to young ‘Burlat’ sweet cherry trees (Prunus avium L.). In the year of application, both chemicals provided effective growth control over the entire season, with prohexadione-Ca plus ethephon being more restrictive to growth than prohexadione-Ca alone. This pattern of growth suppression was observed in the dynamics of shoot elongation, mean shoot length, internode length, and total shoot extension. Both chemical treatments increased flower bud set on previous-season shoots. Residual effects (i.e., in the year following treatment, with no additional chemical application) were produced by prohexadione-Ca plus ethephon, which reduced the mean shoot length to 56.6% of untreated control trees, and by both treatments significantly limiting the length of all internodes relative to the controls. No residual effects were observed on the numbers of flower buds in year-2.