Effect of Blossom Density and Crop Load on Growth, Fruit Quality, and Return Bloom in ‘Honeycrisp’ Apple

Abstract

<jats:p>From 2003 to 2006, the blossom level and crop load of ‘Honeycrisp’ apple (<jats:italic>Malus × domestica</jats:italic> Borkh.) trees on M.26 rootstocks were adjusted to improve fruit quality and return bloom. The treatments consisted of manually removing flower clusters to 50, 100, and 150 per tree, then at ≈50 d after full bloom, the crop load was adjusted to 3, 6, and 9 fruit/cm<jats:sup>2</jats:sup> trunk cross-sectional area (TCSA), respectively. All flower and crop load adjustment significantly increased TCSA and canopy volume compared with the control. Classic biennial bearing was observed on the untreated control trees and those thinned to 150 blossom clusters per tree and 9 fruit/cm<jats:sup>2</jats:sup> TCSA and was mitigated for trees with 50 and 100 blossom clusters followed by crop load adjustment to 3 and 6 fruit/cm<jats:sup>2</jats:sup> TCSA, respectively. Fruit color the “on” year was always lower on the control trees; no difference was found in the “off” year. The treatments increased fruit weight proportional to crop load except for the 2004 “off” year. This study illustrates that for trees with ≈1 m<jats:sup>3</jats:sup> canopy volume, the combined effects of blossom and crop load adjustment to 100 blossom clusters/tree followed by fruitlet adjustment to 6 fruit/cm<jats:sup>2</jats:sup> TCSA and below will induce consistent annual production for ‘Honeycrisp’.</jats:p>

Partitioning of Dry Matter into Fruit Explains Cultivar Differences in Vigor in Young Olive (Olea europaea L.) Trees

“…These results are in line with previous finding that vegetative growth (i.e., vigor) is reduced by the presence of fruit, which compete for resources (Berman and DeJong, 2003;Castillo-Llanque and Rapoport, 2011;Chandler and Heinicke, 1926;Connor and Fereres, 2005;Costes et al, 2000;Dag et al, 2010;Embree et al, 2007;Forshey and Elfving, 1989;Lauri and T erouanne, 1999;Lavee, 2007;Mochizuki, 1962;Monselise and Goldschmidt, 1982;Obeso, 2002;Rallo and Su arez, 1989;Salazar-García et al, 1998;Stevenson and Shackel, 1998;Verheij, 1972). This is not to say, however, that more abundant fruiting cannot be a consequence, rather than the cause, of reduced vigor.…”

“…This is the case for mature trees of many species (Berman and DeJong, 2003;Costes et al, 2000;Lauri and T erouanne, 1999;Salazar-García et al, 1998;Stevenson and Shackel, 1998), including olive (Castillo-Llanque and Rapoport, 2011;Connor and Fereres, 2005;Dag et al, 2010;Lavee, 2007;Monselise and Goldschmidt, 1982;Obeso, 2002;Rallo and Su arez, 1989). In young trees, the removal of all blossoms or fruits results in dramatic increases in growth relative to the fruiting trees (Chandler and Heinicke, 1926;Embree et al, 2007;Forshey and Elfving, 1989;Mochizuki, 1962;Verheij, 1972). Similarly, earlier and more abundant fruiting (i.e., higher partitioning into fruit) is at least one of the mechanisms involved in the effect of dwarfing rootstocks (Avery, 1970;Preston, 1958) and in some cases, the only mechanism (Lliso et al, 2004), although in other cases, it is probably not the only one.…”

Optimizing Crop Load for New Apple Cultivar: “WA38”

“…Biennial bearing is the natural tendency of some apple cultivars to set a heavy crop load one year ("on" year), and a minimal crop load in the following year ("off" year) [21]. Crop load management techniques (i.e., bloom/green-fruit thinning) were shown to be effective in reducing biennial bearing, as well as enhancing canopy growth, increasing fruit size, and producing consistent high-quality fruit [9,18,[22][23][24]. Also, some disorders like bitter pit can be related to poor crop load management [20].…”

“…Precision crop load management consists of three different steps: winter pruning (flower bud removal), blossom thinning at bloom, and green-fruit thinning during cell division [22]. The culmination of these horticultural tasks should aim to result in an appropriate number of fruit sinks for a balanced carbon supply and optimal fruit size, yield, and quality [25].…”

“…Fruits from lighter cropped trees produced higher-quality fruit and resulted in longer storability [20]. Embree et al [22] noted that "Honeycrisp" can produce consistent high-quality fruit in Nova Scotia (Canada), but only under optimal crop level conditions. Embree et al's [22] results indicated that a crop load level of 6 fruits/cm 2 of trunk cross-sectional area (TCSA) yielded high-quality fruit and mitigated biennial production.…”