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Joann M. McLaughlin and Duane W. Greene

Fruit-bearing limbs of five apple (Malus domestics Borkh.) cultivars varying in degree of biennial bearing were either unsprayed or received five repeat applications of BA at 50 mg·liter-1 with daminozide at 2000 mg·liter-1. BA and daminozide increased early appendage formation of potential flower buds, but this increase was sustained only on `Early McIntosh' and `Baldwin'. BA and daminozide increased return bloom on all treated limbs, with the exception of `Early McIntosh'. The annually bearing cultivars McIntosh and Delicious initiated 20 appendages before the formation of floral parts, while the biennially bearing cultivars Golden Delicious, Baldwin, and Early McIntosh initiated 19, 18, and 22 appendages, respectively. Flower removal before bloom increased appendage formation on the biennial cultivar Baldwin but not on the annual cultivar Delicious. Chemical names used: N -(phenylmethyl) -1 H-purine-6-arnine (BA); butanedioic acid mono(2,2-dimethyihydrazide) (daminozide).

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Joann M. McLaughlin and Duane W. Greene

Combination postbloom sprays of BA at 50 mg·liter-1 and daminozide at 2000 mg·liter-1 were made to limbs of `Early McIntosh' apple (Malus domestics Borkh.) where all of the flowers were either removed before full bloom or allowed to remain. BA and fruit removal increased return bloom, whereas daminozide bad no effect. No treatment had a consistent effect on spur leaf area. Repeat sprays of GA4+7 to `Delicious' apple trees at full bloom (FB) +5, FB + 14, and FB +22 days reduced appendage development and flower bud formation on spurs. One spray of GAd+7 at 150 mg·liter-1 at FB +42 days reduced appendage formation and the percentage of flowering spurs but not as effectively as earlier repeat sprays of GA4+7 at 50 mg·liter-1 When BA at 150 mg·liter-1 was combined with the GA at FB +42 days, appendage formation was increased but the reduction in flowering was not reversed. One BA spray at 50 mg·liter-1 at FB +22 days to `McIntosh' trees increased the number of appendages formed in spurs, but return bloom was not influenced. Chemical names used: (N -phenylmethyl) -1 H -purine-6-amine (BA); butanedioic acid mono (2, 2-dimethylhydrazide) (daminozide); gibberellins A4 and A7 (GA4+7).