Thinning `Fuji' Apple Blossoms with Synthetic Auxins (MCPB-ethyl or NAA) and Ethephon with or without Postbloom Thinning with Carbaryl

Abstract

<jats:p>Three experiments were conducted at two locations, two at Summerland, British Columbia, Canada and one at Corvallis, Ore., to evaluate synthetic auxins (MCPB-ethyl or NAA) and ethephon as blossom thinners for `Fuji' apple [<jats:italic>Malus sylvestris</jats:italic> (L.) Mill var. <jats:italic>domestica</jats:italic> (Borkh.) Mansf.]. These experiments also involved application of carbaryl at 1000 mg·L<jats:sup>-1</jats:sup> in the postbloom period. All blossom thinners were sprayed at 85% full bloom while carbaryl was applied at 11-mm fruit diameter. Within these experiments, MCPB-ethyl at up to 20 mg·L<jats:sup>-1</jats:sup> or NAA at up to 21 mg·L<jats:sup>-1</jats:sup> increased whole flower cluster removal linearly with rate; however, with the Corvallis experiment MCPB-ethyl failed to result in any thinning. Neither auxin treatment consistently reduced fruit set on the remaining clusters, resulting in “clustering”. Bloom-time application of ethephon at 100 mg·L<jats:sup>-1</jats:sup> with NAA further reduced crop load. Carbaryl reduced total crop load by increasing both whole cluster removal and number of sites with a single fruit. Return flowering was not improved by the auxin treatments except where there was very excessive crop reduction. Ethephon or carbaryl promoted return flowering with the carbaryl effect being more pronounced. However, this carbaryl effect was significantly countered by the bloom-time auxin whereas ethephon overcame the negative effects of the auxin treatments. The combined use of ethephon and carbaryl was effective in terms of both crop reduction and return flowering benefits. Chemical names used: 1-naphthyl N-methylcarbamate (carbaryl); 2-chloroethylphosphonic acid (ethephon); ethyl 4-(4-chloro-2-methylphenoxy) butanoate (MCPB-ethyl); and 2-(1-naphthyl) acetic acid (NAA).</jats:p>

The effect of fruit-setting hormones applied at the stage of flowering on the morphological and physiological characteristics of eggplant (Solanum melongena L.) fruit during growth, maturation and storage

“…This result agrees with previous reports where the application of different commercial auxins did not affect the firmness of pepper (Lopez-Elias et al, 2005;Salas et al, 2009), although in other species, e.g. apple (Guak et al, 2002;Curry (2006) and kiwifruit (Bregoli et al, 2006), hormones have been reported to increase fruit firmness. By contrast, in stone fruit species, e.g.…”

Comparing Novel Sweet Cherry Crop Load Management Strategies

“…For many other tree fruit species, crop load is managed by blossom-and post bloom thinning agents to improve fruit quality and reduce fruit number and total sink demand per tree (Westwood, 1993). Indeed, improvements in apple fruit quality (Guak et al, 2002;Lakso et al, 2001) and value (Marini, 2002;Stover et al, 2001) in response to chemical thinning have been reported. Similar results have been reported for peach (P. persica) (Genard et al, 1999;Miranda-Jimenez and Royo-Diaz, 2002).…”

Profiling of phytohormones in apple fruit and buds regarding their role as potential regulators of flower bud formation

“…In previous studies, field trials using synthetic auxin analog NAA for the treatment of apple trees did not support the theory of inhibitory effect of auxins on flower bud initiation. Spraying of apple trees with NAA did not reveal negative effects of this compound on return bloom ( Guak et al. 2002 ).…”

“…2013 , Stopar 2010 , Zabrkić et al. 2011 ) or did not significantly affect return bloom of the experimental trees ( Guak et al. 2002 ).…”