Prohexadione-calcium Inhibits Apple, but not Peach, Tree Growth, but Has Little Influence on Apple Fruit Thinning or Quality

Abstract

In northern Virginia, over 80% of the apple crop is grown for processing. Many trees are propagated on vigorous rootstocks and require much pruning, especially in the tops. To reduce costs and labor needs, many growers prune every second or third year. When trees are not pruned, shading caused by growth in the current season or in nonpruned years is detrimental to pest control, fruit quality, and yield.Several plant growth regulators have been evaluated for their potential to reduce vegetative growth of tree fruits, thereby reducing pruning costs and improving fruit quality. Several reviews (Faust, 1984;Looney, 1983;Luckwill, 1970;Miller, 1988;Williams, 1984) dealing with many of these compounds indicate that most have several effects of greater commercial value than control of vegetative growth.The objectives of the experiments reported here were to evaluate the effects of prohexadione-calcium (3-oxido-4-propionyl-5-oxo-3cyclohexene-carboxylate), formulated as BAS-125 ("Apogee" ® ), on a) vegetative growth of apple and peach trees, b) fruit size and quality, and c) response to thinning chemicals. MATERIALS AND METHODSGeneral. Randomized complete-block designs were used in all experiments. Trees were blocked by location within rows, by rootstock, and/or by flower density rating. All experiments had six blocks except for Expts. 1, 4, 5, and 6. Trees were sprayed with either a low pressure hand-wand sprayer or a Swanson three-point-hitch airblast sprayer with both fans adjusted to one side, which doubled air output and increased nozzle numbers.In several experiments (Expts. 1-4), a 10-fruit sample was collected from each tree at harvest for quality evaluations, which included flesh firmness, soluble solids concentration, starch staining, percentage of red color, and incidence of water core. Flesh firmness of both peach and apple fruit was measured on two sides of each fruit with an Effegi penetrometer (model FT327; McCormick Fruit Tech, Yakima, Wash.) fitted with an 11.1-mm tip. Soluble solids concentration (SSC) was estimated with an Atago hand-held refractometer (model N1; McCormick Fruit Tech), utilizing a composite sample of juice resulting from penetrometer testing for each replicate of each treatment. Each apple fruit was cut in half transversely, and severity of water core was rated on a scale of 0 to 5 (0 = none, 5 = severe). Flesh starch was evaluated by dipping half of each apple in a solution of I 2 /KI for ≈15 s. The degree of staining was rated on a scale of 0 to 5 where 1 = staining of the entire cut surface and 5 = absence of starch (Poapst et al., 1959).In the dormant season (Expts. 1-4), average shoot length of the longest top two shoots, length of the five longest scaffold shoots, total length of shoots longer than 30 cm, weight and basal and terminal shoot diameters of these scaffold shoots, nodes/cm of the basal 40 cm, nodes/cm of the upper 30 cm of shoots, and time required to prune each tree, number of cuts/tree, and pruning weights/cm 2 trunk cross-sectional area (TCSA) per tree were recorded...

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Effect of Prohexadione Calcium on Growth Components and Endogenous Gibberellins Contents of Rice (Oryza sativa L.)

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Pseudomonas syringaeDiseases of Fruit Trees: Progress Toward Understanding and Control

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