Effects of 2,4-D and related substances on fruit-drop, yield, size, and quality of Valencia oranges
AuthorsW. S. Stewart
H. Z. Hield
B. L. Brannaman
Authors AffiliationsW. S. Stewart was Formerly Associate Plant Physiologist in the Experiment Station, now with the Pineapple Research Institute, Honolulu, T.H; H. Z. Hield was Laboratory Technician in the Experiment Station; B. L. Brannaman was Senior Laboratory Technician in the Experiment Station.
Hilgardia 21(11):301-329. DOI:10.3733/hilg.v21n11p301. March 1952.
During 1947 and 1948, in various districts throughout southern California, 29 comparisons were made between fruit-drop from non-sprayed Valencia orange trees and that from trees sprayed with 2,4-D at concentrations from 4 to 48 p.p.m. Application of 2,4-D at low volumes was made six months before drop, as well as after drop had begun. While the average reduction in fruit-drop from the sprayed trees was 35.1 per cent, in some cases it was as high as 64, and in others, as low as 5 per cent.
Studies were also made of the possibility of increasing fruit size of Valencias by use of 2,4-D. In an experiment begun in 1948, 17 different chemicals were applied to Valencia trees at full bloom. Only 2,4-D and 2,4,5-T induced a significant increase in fruit size. Data were obtained from eight additional experiments using actual field-scale applications. Determinations of the effect of the sprays on size and grade of fruit were based on packing house information. As a result of the spray, there was a gain of 28.0 packed boxes of fruit size 220 and larger, and a decrease of 19.8 boxes of fruit size 252 and smaller, per 100 trees sprayed.
Periodic measurements showed that larger fruit sizes resulting from use of 2,4-D were due to an increased growth rate. As fruits grew older, they seemed to become less responsive to 2,4-D. In commercial practice, it is suggested that during the 16-week period after flowering, this diminishing response be compensated for by corresponding increases in the concentration of 2,4-D applied.
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Effects of 2,4-dichlorophenoxyacetic acid and 2,4,5-trichlorophenoxyacetic acid on fruit drop, fruit production and leaf drop of lemon trees. Amer. Soc. Hort. Sci. Proc. 1950b. 55:163-71.
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Stewart W. S., Klotz L. J., Hield H. Z. 2,4-D sprays for control of navel orange drop. Calif. Citrogr. 1947. 33:49 77, 78, 79
Effects of 2,4-D and related substances on fruit-drop, yield, size, and quality of Washington Navel oranges. Hilgardia. 1951. 21(7):161-93.
Stewart W. S., Parker E. R. Preliminary studies on the effects of 2,4-D sprays on preharvest drop, yield, and quality of grapefruit. Amer. Soc. Hort. Sci. Proc. 1947. 50:187-94.
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Also in this issue:Baled vs. cubed alfalfa hay, for ewes and lambs
Effects of relative humidity on Irish potatoes in storage
Effects of irrigation practices on safflower yield in San Jbaquin Valley
Sunken mottle of Honey Dew melons
Chemical attractants for navel orangeworm moths
Irrigation and nitrogen for cotton… a yield surface and optimum combinations on a Panoche loam soil
Insect damage to sesame… and control possibilities