Vol. 81 No: 3

Title:
Application of 2,4-dichlorophenoxypropionic acid 2-ethylhexyl ester reduces mature fruit abscission in Citrus navel cultivars

Authors:
M. AGUSTÍ, M. JUAN, A. MARTÍNEZ-FUENTES, C. MESEJO, C. REIG and V. ALMELA

pp: 532-536

Abstract:
2,4-dichlorophenoxyacetic acid (2,4-D) isopropyl ester has been used extensively, since the 1950`s, to reduce mature fruit abscission in Citrus navel cultivars. However, this synthetic auxin is no longer registered for this purpose in the European Union (EU). 2,4-dichlorophenoxypropionic acid (2,4-DP) 2-ethylhexyl ester has been registered in the EU for use in citrus growing and can be an effective replacement for 2,4-D to reduce pre-harvest fruit abscission. Use of the 2-ethylhexyl ester of 2,4-DP sprayed before mature fruit abscission significantly reduced fruit drop in sweet orange (Citrus sinensis L. Osbeck) ´Washington navel` and ´Navelate`. The magnitude of the response depended on the concentration applied. At 15 mg l^-1, the percentage of abscised fruit was reduced by 50-75% compared to untreated trees, depending on the variety and the orchard. Increasing the concentration applied to 50 mg l^-1 did not improve this response.The response to this auxin was as effective as that obtained with 2,4-D applied on the same day at the same concentration (15 mg l^-1). 2, 4-DP treatment had no effect on skin colour or on the internal and external characteristics of the fruit at harvest.

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