The Effect of Repeat Annual Applications of Prohexadione–calcium on Fruit Set, Return Bloom, and Fruit Size of Apples

Abstract

<jats:p>Prohexadione–calcium (ProCa) is used routinely in orchards to control vegetative growth and to reduce the shoot blight phase of fire blight. This communication reports on multiple-year applications of ProCa with special emphasis on treatment effects on fruit set, fruit size, and return bloom. Increased fruit set was confirmed from high rates of ProCa above 125 mg·L<jats:sup>−1</jats:sup>. The increase in fruit set was attributed primarily to a reduction of abscission during June drop rather than an increase in initial set. ProCa decreased fruit weight in some instances. Part of this reduction could be attributed to increased fruit set. However, the large reduction in fruit weight at harvest could only be explained by a direct effect of ProCa when used at high rates. When ProCa was applied as a concentrate spray at 250 mg·L<jats:sup>−1</jats:sup>, terminal growth was reduced comparable to the application made as a tree row volume dilute spray (1×). However, fruit set was increased when the spray volume in which ProCa was delivered was reduced to 4×. A range of ProCa rates was used on ‘Mutsu’. An initial application rate of 42 mg·L<jats:sup>−1</jats:sup> followed by similar subsequent rates controlled growth comparably to higher initial and total rates, yet low rates had no effect on fruit weight or return bloom. Low rates of ProCa appear to be effective at controlling vegetative growth yet appear to have minimal side effects. High rates, especially those intended to reduce fire blight, come with the risk of increased fruit set and reduced fruit size and return bloom.</jats:p>

Mango Flower Induction in the Brazilian Northeast Semi-Arid With Gibberellin Synthesis Inhibitors

“…plant -1 , increased the fruit mass of 15.7 and 10.8% respectively, as compared to control (Table 1). These results confirm those obtained on other species (Petri and Leite, 2005;Greene, 2008). Low dosages of ProCa, 42 mg L -1 , were more effective in vegetative growth control, whereas higher dosages tend to reduce fruit weight, besides compromising the flowering of the following cycle.…”

Controle do crescimento vegetativo e floração de mangueiras cv. Kent com reguladores de crescimento vegetal

“…Os tratamentos com a aplicação de PBZ isolado e associado com o ProCa reduziram significativamente o comprimento do fluxo vegetativo, em 39,5% e 67,5%, respectivamente, em relação ao controle (Tabela 1). O ProCa, considerado instável e com curto tempo de persistência na planta, em torno de 10 a 14 dias em macieiras, induz resposta rápida na inibição do crescimento vegetativo (ZADRAVEC et al, 2008;GREENE, 2008GREENE, , 2010, e principalmente quando associado ao PBZ, aplicado via solo, permite maior eficiência no controle do vigor das brotações.…”

Development of Peach Flower Buds under Low Winter Chilling Conditions

“…Most of them act as inhibitors to the synthesis of GAs, and some induce the formation of ethylene [159,161]. One of these compounds, ethephon, when applied to the branches and other plant tissues reduces the level of auxins in the branch apical meristems, thereby reducing growth [159,163].…”

“…It acts on the enzyme GA 20-3 , reducing the formation of GA 1 , and has been widely used for vegetative growth control in apple and pear due to the fact of its low toxicity and limited persistence with a low risk to the consumer and environment. However, it has a short duration of activity and more than one application is often necessary [56,159,[163][164][165][166].…”

“…Trinexapac-ethyl significantly reduces the concentration of active GA 1 , inhibiting the action of the 3b-hidroxilase enzyme, and increasing the GA 20 biosynthesis precursor [167]. Although it has been used to control the growth of wheat, sugarcane, and other grasses, its use in fruit crops is still limited, and further studies on its effects are necessary [163].…”