Prediction and control of bitter pit in apples. II. Control by summer pruning, fruit thinning, delayed harvesting and soil calcium dressings

TL;DR: Summer pruning and fruit thinning did not seriously affect fruit storage quality and there was some evidence that late picking decreased bitter pit incidence, and liming lessened the incidence of bitter pit slightly after several successive years of treatment.

Abstract: SummaryVarious orchard treatments were investigated as alternative or supplementary measures to routine spraying with Ca(NO3)2 solutions for the control of bitter pit in stored Cox’s Orange Pippin and James Grieve apples. The leaf/fruit ratio was modified by summer pruning and fruit thinning, and picking date was delayed while, in orchards on sandy soils, Ca was applied either as CaCO3 or CaSO4 directly to the soil. Summer pruning produced a slight improvement in the storage quality of larger fruits from unsprayed trees. Spraying lowered the incidence of both bitter pit and breakdown, and reduced external bitter pit to such an extent that no additive effect of pruning was discerned. Fruit thinning at the end of June or in early July did not seriously affect fruit storage quality and there was some evidence that late picking decreased bitter pit incidence. In four trials in Cox orchards on sandy soils liming lessened the incidence of bitter pit slightly after several successive years of treatment. Although...