Large, protruding navel-end openings of navel oranges (Citrus sinensis (L.) Osbeck) are a major cull factor in the packhouse and make the control of some insects very difficult. Previous work on navel orange trees suggested that the synthetic auxin, 2,4-dichlorophenoxyacetic acid (2,4-D), applied at full bloom at 20 mg·L-1 reduced the diameter of the navel-end opening. In a preliminary study to verify these results under South African conditions, similar results were obtained when 2,4-D was applied at 25 mg·L-1 at petal drop on ‘Palmer’, ‘Robyn’ and ‘Lane Late’ navel orange trees. To determine the optimal timing and concentration of application without any detrimental effects on fruit quality, 2,4-D was applied at 15, 25 or 35 mg·L-1 at either full bloom or petal drop to ‘Washington’ navel orange trees in the following season.
Rootstocks and Plant Water Relations affect Sugar Accumulation of Citrus Fruit via Osmotic Adjustment
The aim of the study is to determine how rootstock types affects sugar accumulation in Citrus fruit. This was tested by using controlled water-deficit stress during phase II of fruit growth, that causes active osmotic adjustment by increasing the solute concentration in fruit due to sucrose being hydrolyzed to fructose and glucose.
The efficacy of applying biocontrol agents, chemical fungicide and nematicide as protective treatments against the soilborne parasites, Fusarium spp. (Fusaria) and citrus nematode Tylenchulus semipenetrans Cobb was evaluated. The experiment took place under field conditions in a citrus orchard cultivated with 16-year-old sweet orange (Citrus sinensis L.) osbech cv. Valencia trees grafted on sour orange (C. aurantium L.) rootstock during the growing season November 2006/ October 2007. This orchard is located at Bader district, Behera governorate, Egypt. The populations of soil fauna and flora under trees canopy were examined just before treatment, and 1, 3, 6, 9 and 12 months after the treatment application. A visual inspection for the appearance of symptoms related to Fusarium or nematode infection on treated and untreated citrus trees was carried out periodically every two weeks throughout the experimental period.