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How to Manage Pests
UC Pest Management Guidelines
Citrus
Increasing Fruit Size with 2,4-D
(Reviewed 7/03,
updated 7/03)
In this Guideline:
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Amount to Use
(g a.e./a = grams acid equivalent/acre) |
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| Variety |
Time |
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| CAUTION: Avoid 2,4-D spray drift to susceptible
plants, which include cotton, grapes, roses, beans, peas, alfalfa,
lettuce, ornamentals, and all broadleaf species. |
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| A. |
VALENCIA
and NAVEL
ORANGES* |
23 g a.e./a in water spray
...or...
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3/16-1/4 inch
(5-6 mm)
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30 g a.e./a in water spray
...or...
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1/4-1/2 inch
(6-13 mm)
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38 g a.e./a in water spray
...or...
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1/2-5/8 inch
(13-16 mm)
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45 g a.e./a in water spray |
5/8-3/4 inch
(16-19 mm)
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COMMENTS: Fruit-sizing sprays require excellent coverage.
May cause an increased roughness of the rind. For Valencia oranges,
also controls mature fruit drop and may slightly delay granulation
in new crop. For navel oranges, may decrease fruit splitting. |
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| B. |
GRAPEFRUIT* |
23 g a.e./a in water spray
...or...
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1/4-3/8 inch
(6-9 mm)
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30 g a.e./a in water spray
...or...
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3/8-5/8 inch
(9-16 mm)
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38 g a.e./a in water spray
...or...
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5/8-3/4 inch
(16-19 mm)
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45 g a.e./a in water spray |
3/4-1 inch
(19-25 mm)
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COMMENTS: Fruit-sizing sprays require excellent coverage.
Also controls mature fruit drop. |
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Note:
(1) Do not apply to trees less than 6 years old. (2) Do not apply
within 7 days of harvest. (3) Do not enter or allow worker entry into
treated area during the restricted entry interval (REI) of 12 hours.
(4) Use an isopropyl ester formulation of 2,4-D containing 3.34 or
3.36 lb of acid equivalent per gallon. These formulations provide
about 1520 g acid equivalent/gal, 402 g acid equivalent/liter, 0.402
g acid equivalent/ml, or 12 g acid equivalent/fl oz. An example for
30 g acid equivalent/acre: (30g) /(0.402 g/ml) = 75 ml. Thus, 30 g
would be contained in 75 ml or 2.5 fl oz of formulation. Apply this
to 1 acre in volumes up to 500 gal. (Added to 500 gal it would be
a 16 ppm solution). If spray volumes exceed 500 gal/acre, follow restrictions
specified on the label. |
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UC IPM Pest Management Guidelines: Citrus
UC ANR Publication 3441
Plant Growth Regulators
C. W. Coggins, Jr., Botany and Plant Sciences, UC Riverside
C. J. Lovatt, Botany and Plant Sciences, UC Riverside
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