25 Mar 2025
Mandarin

Canopy position affects pigment expression and accumulation of flavedo carbohydrates of ‘Nules Clementine’ Mandarin Fruit, thereby affecting rind condition

Because photosynthesis provides the required carbohydrates for fruit development and respiration releases the stored energy from these carbon compounds, interalia during postharvest storage, it is therefore important that fruit tissues have an adequate carbohydrate concentration at the start of the postharvest period to ensure optimal storage life. In addition to photosynthate supply from leaves, the chlorophyll-containing flavedo of citrus (Citrus sp.) fruit (outer, colored part of the rind) has the ability to fix CO2 through its own photosynthetic system. In this experiment, spanning three seasons, the three main sugars (sucrose, glucose, and fructose) were quantified in the flavedo of ‘Nules Clementine’ mandarin (Citrus reticulata) fruit during Stages II and III of fruit development. Flavedo was sampled from fruit borne on the inside (low light intensity) or outside (high light intensity) of the tree’s canopy. In one season, the photosynthetic and respiration rates of fruit borne in the two canopy positions were measured pre- and post-color break (March and April, respectively).

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28 Feb 2025

Influence of deficit irrigation in phase III of fruit growth on fruit quality in ‘lane late’ sweet orange

The aim of this work was to apply one strategy of deficit irrigation (DI) to improve the final fruit quality in 10-year-old ‘Lane late’ sweet orange grafted on Carrizo citrange (Citrus sinensis L. Osb. x Poncirus trifoliata L.). The experiment was carried out over 2 years in an experimental orchard located in Torre Pacheco (Murcia, south-east Spain). The deficit irrigation treatment consisted of the stopping of irrigation in phase III of fruit growth (1st October–28th February). The irrigation cut-off in phase III reduced the midday stem water potential, the plant water status being heavily influenced by rainfall. In both years, the DI treatment did not alter fruit yield although mean fruit weight was slightly reduced.

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24 Jan 2025
Shade cloth over citrus

FINAL REPORT: Integrated pest management under nets in the Western Cape

We investigated the incidence of citrus pests under netted and in open orchards. Two sites with paired netted and open orchards in the Western Cape were used in the study, one near Porterville and one near De Doorns. Netting differed in the extent of coverage and maintenance of tears. The study found that pests differed more between sites than between open or netted orchards. The differences between pests in netted and open orchards was more pronounced when netting reached to the ground and was repaired regularly.

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25 Nov 2024

Fruit thinning chemical agents improves fruit size and quality in ‘kinnow’ Mandarin

‘Kinnow’ mandarin (Citrus reticulata Blanco) fruit needs to be thinned to increase the availability of photosynthates used to increase fruit size, fruit quality, profitability and can also help to overcome alternate bearing. This study evaluated ‘Kinnow’ fruit thinning using three chemical agents with different levels of concentration i.e. naphthalene acetic acid (NAA) @ 0.2, 0.3, 0.4, and 0.5 gL 1; 3,5,6 trichloro 2 pyridyloxyacetic acid (3,5,6 TPA) at TPA at 0.2, 0.5, and 0.7 gL 1, and ethephon @ at 0.4, 0.5, and 0.6 gL 1, in Pakistani orchards just after the June fruit drop for two growing seasons 2017 19. Fruit weight was increased due to chemical thinning application when compared with the respective controls.

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21 Oct 2024
Post harvest citrus

Alternative methods for the control of postharvest citrus diseases

The postharvest diseases of citrus fruit cause considerable losses during storage and transportation. These diseases are managed principally by the application of synthetic fungicides. However, the increasing concern for health hazards and environmental pollution due to chemical use has required the development of alternative strategies for the control of postharvest citrus diseases. Management of postharvest diseases using microbial antagonists, natural plant-derived products and Generally Recognized As Safe compounds has been demonstrated to be most suitable to replace the synthetic fungicides, which are either being banned or recommended for limited use.

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21 Oct 2024
Girdling

Influence of girdling on the seasonal leaf nutrition status and fruit size of Robinson Mandarin

This study was undertaken to investigate the effects of single and double girdling applications on the fruit yield, commercial size, quality, photosystem II (PSII), leaf chlorophyll and leaf nutrition content of 22-year-old Robinson mandarin (Citrus reticulata). Girdling treatments were performed at anthesis (when 60% of the flowers were opened) with approximately 5 mm trunk diameter in 2014. The fruit was harvested in 2014 at the optimum harvest time (in December) for fruit yield, properties and size. Evaluations of leaf mineral content, chlorophyll concentration and fluorescence measurements were performed at monthly intervals.

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21 Oct 2024
Navel Sweet Orange

Optimal timing of application of 2,4-D on ‘Navel’ sweet orange reduces the size of the navel-end

‘Navel’ sweet orange [Citrus sinensis (Osbeck)] fruit with large, open, or protruding navel-ends are predisposed to splitting and navel-end rot, and provide an entry point that hampers the control of insect pests. A reliable method to reduce the size of navel-ends, without compromising tree health or fruit quality, would provide multiple benefits.The objective of this study, was to determine the optimal timing and concentration of foliar spray treatments with the synthetic auxin, 2,4-dichlorophenoxyacetic acid (2,4-D), to reduce the size of the navel-end on ‘Newhall Navel’ and ‘Washington Navel’ sweet orange fruit. The effects of 2,4-D treatment on fruit yield, tree health, and fruit quality, were also assessed.Treatments were applied to ‘Newhall Navel’ trees at a rate of 25 mg l–1 2,4-D at 2-weekly intervals, starting at full bloom (FB), and continuing until 4 weeks after 100% petal drop (PD). On ‘Washington Navel’ trees, 2,4-D was applied at 15 mg l–1, 25 mg l–1, or 35 mg l–1 at FB, or at 100% PD.

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