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26 Oct 2022
Climate change on Citrus
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The Future of Citrus Fruit: The impact of climate change on citriculture.

Current citriculture is threatened by climate change. The increase in temperature, together with other adverse climate phenomena, is modifying the environmental conditions in the regions where citrus varieties are currently being developed. The detrimental effects of these adverse environmental factors on citrus physiology and production, such as drought or augmented soil salinity, will likely increase because of elevated temperatures, which will jeopardise crop production and, in extreme cases, even plant survival.

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26 Oct 2022
Citrus Pests
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Sustainability in Brazilian Citriculture: Three Decades of Successful Biological Control of Insect Pests

Citrus insect pests has grown worldwide, concerning entomologists and farmers especially because of the high demand for food that makes it to our tables. The use of pesticides brought several issues, such as the negative impacts on the human health, pollution, and insect resistance. In this context, more environmentally-friendly strategies have been demanded by governments and consumers. In this review, we present three remarkable examples of pest management in Brazil that involved many researchers from different expertise areas to develop more sustainable strategies to reduce the damages to citrus production.

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30 Sep 2022
Washington Navel Orange
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Effects of NAA and GA3 Sprays on Fruit Size and the Incidence of Creasing of ‘Washington’ Navel Orange

‘Washington’ navel orange [Citrus sinensis (L.) Osb.] orchards in Israel suffer from creasing – a physiological disorder of the fruit, leaving the fruit unsuitable for the fresh fruit market. Many ‘Washington’ navel orchards tend to bear small size fruit with low market value. This paper presents two experiments, in which the effects of naphthaleneacetic acid (NAA, 300 mg·L-1) on yield, fruit size, fruit quality and the incidence of creasing of ‘Washington’ navel orange were examined. The NAA effects were compared to those of gibberellic acid (GA3, 20 mg·L-1) – the common treatment for creasing reduction. In the first experiment, 36% of the fruit of the control trees suffered from severe creasing. The NAA sprays in May (at 18-mm fruitlet diameter) and in June (at 30-mm fruitlet diameter) reduced the incidence of creasing to 9 and 6% respectively, while the GA3 spray at August reduced the incidence of creasing to 17% of the fruit.

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29 Sep 2022
Citrus Flowering
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Gibberellic acid in Citrus spp. flowering and fruiting: A systematic review

In Citrus spp., gibberellic acid (GA) has been proposed to improve different processes related to crop cycle and yield. Accordingly, many studies have been published about how GA affects flowering and fruiting. Nevertheless, some such evidence is contradictory and the use of GA applications by farmers are still confusing and lack the expected results.

This review aims to collate, present, analyze and synthesize the most relevant empirical evidence to answer the following questions: (i) how does gibberellic acid act on flowering and fruiting of citrus trees?; (ii) why is all this knowledge sometimes not correctly used by farmers to solve yield problems relating to flowering and fruit set?

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31 Aug 2022
Girdling Branches
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Delay of early fruitlet abscission by branch girdling in citrus coincides with previous increases in carbohydrate and gibberellin concentrations

Current evidence in citrus indicates that gibberellins (GAs) are main determinants of early fruit set while subsequent growth of developing fruits is mostly dependent upon carbohydrate availability. In this work, branch girdling performed at anthesis in Satsuma mandarin (Citrus unshiu (Mak.) Marc.) cv. Okitsu transitorily reduced early abscission rates (12–32 days after anthesis, DAA) delaying initially the process of natural fruitlet drop. The effects of girdling on growth, gibberellin (GA) and carbohydrate concentrations in developing ovaries and fruitlets were assessed during this initial growth stage (0–69 DAA). In girdled branches, abscission rate reduction was preceded by elevated concentrations of carbohydrate and GA in developing ovaries and fruitlets.

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21 Jul 2022
Leaf Abscission
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Abscisic Acid Reduces Leaf Abscission and Increases Salt Tolerance in Citrus Plants

This paper describes the physiological effects of abscisic acid (ABA) and 100 mM NaCl on citrus plants. Water potential, leaf abscission, ethylene production, photosynthetic rate, stomatal conductance, and chloride accumulation in roots and leaves were measured in plants of Salustiana scion [Citrus sinensis (L) Osbeck] grafted onto Carrizo citrange (Citrus sinensis [L.] Osbeck · Poncirus trifoliata [L.] Raf) rootstock. Plants under salt stress accumulated high amounts of chloride, increased ethylene production, and induced leaf abscission. Stomatal conductance and photosynthetic rates rapidly dropped after salinization.

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23 Jun 2022
Valencia
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Effect of Different Rates of Sulphur Fertilization on Fruit Yield and Leaf Mineral Composition of ‘Valencia’ Oranges in the Subtropical Environment of South Africa

Although sulphur is one of the essential nutrients for plant growth with a crop requirement similar to phosphorus (P), this nutrient element has received little attention because it is supplied in insecticides, fungicides, manure and from the atmosphere. With the relaxation of this requirement, and restrictions on sulphur dioxide emissions by industries it has become apparent that sulphur deficiency is widespread throughout the world. The majority of farmers submitting samples for soil and leaf nutrient analysis do not request a sulphur (S) test. This is due to the fact that farmers are still under the impression that there is enough sulphur in the soil.

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23 Jun 2022
Foliar Fertilizer
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Properly Timing Foliar-applied Fertilizers Increases Efficacy: A Review and Update on Timing Foliar Nutrient Applications to Citrus and Avocado

Foliar fertilization efficiently meets the nutrient demand of tree fruit crops during periods when soil conditions (low or high temperatures, low or excess soil moisture, pH, salinity) render soil-applied fertilizers ineffective, when nutrients (e.g., phosphate, potassium, and trace elements) become fixed in the soil, and when tree nutrient demand is high. Applying nutrients directly to leaves ensures that the metabolic machinery of the tree is not compromised by low availability of an essential nutrient. It should be noted that phloem mobile nutrients applied to the foliage are translocated to all tree parts, even feeder roots.

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