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The influence of exogenously
applied 2,4-dichlorophenoxyacetic acid on fruit drop and
quality of navel oranges (Citrus sinensis L.)
D. M. Modise1,
A. S. Likuku2, M. Thuma2 and R. Phuti2
1College
of Agriculture and Environmental Sciences, University of
South Africa, P.O. Box 392, Pretoria. 0003. South Africa.
2Faculty
of Agriculture, Botswana College of Agriculture, P/Bag 0027,
Gaborone, Botswana
*Corresponding author. E-mail:
modisd@unisa.ac.za.
Accepted
10 November, 2008 |
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Orchard
experiments were carried out in Botswana with the objective
of evaluating the effect of 2,4-dichlorophenoxyacetic acid
(2,4-D) on reducing premature fruit drop. Different
concentration levels of the 2,4-D (8, 16 and 20 mg/L were
applied exogenously to mature fruit trees of sweet orange (Citrus
sinensis L.) in the 2004/2005 season. In the 2005/2006
season the 2,4-D treatments ranged from 20 to 40 mg/L
concentration. There appeared a general increase in fruit
drop for the month of October in all treatments but a
decrease in fruit drop was observed in the fruit trees with
16 and 20 mg/L 2,4-D concentration, that is, from
November through February; with the latter showing the least
number of fruits that dropped throughout the execution of
the experiments. The application of 20 mg/L 2,4-D
significantly reduced fruit drop by more than 50% but higher
concentration levels of the plant growth regulator
significantly increased fruit drop. It was also evident
that, small sized fruits were more susceptible to fruit drop
than larger fruits. These findings suggested
that, 2,4-D can be an effective tool to control fruit drop
by enhancing retention, as well as improving the quality of
navel oranges under dry climatic conditions.
Key
words:
Citrus
sinensis
(L),
fruit drop, plant growth regulator,
2,4-dichlorophenoxyacetic acid. |
