24 May 2024
Citrus flower

Demonstration of a Change in Nitrogen Metabolism Influencing Flower Initiation in Citrus

Changes in the leaf NH3-NH4 + content were monitored during floral induction in Citrus. Five-year-old rooted cuttings of ‘Washington’ navel orange (Citrus sinensis) were induced to flower by subjecting the trees to 8 weeks of low temperature, 8-h day (500 μE m−2 s−1) at 15–18°C/16-h night at 10–13°C and by transferring them afterwards to 12-h day (500 μE m−2 s−1) at 24°C/12-h night at 19°C. Maximum bloom occurred 4 weeks after the transfer to the warmer temperature. The number of flowers and the NH3–NH4 + content of leaves increased significantly (p < 0.05 and P < 0.01, respectively) with the length of the low temperature treatment. Sixteen-year-old ‘Frost Lisbon’ lemon trees (Citrus limon) on ‘Troyer’ citrange rootstocks (C. sinensis × Poncirus trifoliata) under commercial production were subjected to water-deficit stress of increasing severity.

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25 Jan 2024

A Cost-Benefit Analysis for Crop Load

Generating profits in difficult conditions is one of the key drivers for sustainability in agriculture.

In recent years, some citrus producers have struggled to realise good returns as the industry faced a plethora of challenges. These challenges include, but are not limited to the cost of fertiliser, chemical, and fuel that rose rapidly because of the invasion of Ukraine, record freight rates and a decline in market prices.

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24 Jul 2023
Clemgold

ClemenGold International shares its citrus

Around 1,000 tonnes of citrus is to be distributed to disadvantaged communities this year Leading South African citrus company ClemenGold International has said that it is teaming up with a relief organisation to deliver some 1,000 tonnes of citrus to help alleviate the plight of people in some of the country’s poorer communities. “Caring for the communities surrounding our partner farms and packhouses has been a value upon which we’ve acted since the establishment of our business,” explained Adéle Ackermann, marketing manager for ClemenGold International.

“Fruit is our business and donating Vitamin C-rich citrus is a logical way of contributing towards helping communities to thrive.” The company has announced a partnership with SA Harvest, a registered non-profit and leading food rescue and hunger relief organisation, whereby 1,000 tonnes of citrus will be donated during the 2023 season.

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24 Jul 2023
Orange Tree

Winter storms affect Cape growers

With the latest of a series of winter storms sweeping over the South African Western Cape region, citrus and other fruit growers are facing a difficult period of recovery. For the last ten days all citrus harvesting in the Oliphant’s River Valley, the most important region supplying summer citrus to the US, has been suspended. Infrastructure in the Valley and in other parts of the Western Cape has been damaged, with key roads washed away and communities in rural regions flooded.

The winter storms in these regions have been described as the worst since 2008 when floods rose to record levels in places. It comes when significant volumes of South African citrus are due to be discharged in the US later this week, marking the real start of the marketing season. Significant volumes have also been shipped by containers since April. Industry leaders said that before the storms started enough fruit had been packed for the first three vessels, but that their departure could be delayed.

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24 Jul 2023
Brown Rot

Postharvest Strategies for Managing Phytophthora Brown Rot of Citrus using Potassium Phosphite in Combination with Heat Treatments

Phytophthora brown rot, caused by several species of Phytophthora, is an economically important disease of citrus in areas with rainfall during the late stages of fruit development. Recent export restrictions of California orange fruit to China due to the presence of brown rot caused by the quarantine pathogen Phytophthora syringae have mandated more rigorous disease management. We evaluated postharvest applications with the phosphonate fungicide potassium phosphite in combination with heat treatments. In timing studies, potassium phosphite at 1,500 mg/ml was most effective when applied within 18 h after inoculation of orange fruit with P. citrophthora, reducing the incidence of decay by >96% as compared with the control. Potassium phosphite was also highly effective in inoculations with P. syringae. Heated water treatments at 60°C were consistently and highly effective in reducing the incidence of brown rot after inoculation with P. citrophthora, whereas treatments at 55 or 50°C were more variable and generally less effective.

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27 Jun 2023
Flooding

Citrusdal community bands together to get back on their feet after flood

Rain is still falling over Citrusdal where food has had to be flown in by helicopter to stranded inhabitants after the town’s entrance road was washed away, and now the remaining electricity line has also fallen victim to the flood.  It is expected that the rain will ease off from Wednesday. In the port of Cape Town very high swells have meant that vessels couldn’t enter the harbour; there are currently three vessels waiting to come into port.

Repairs to the town bridge over the Olifants River which was washed away are underway, including correcting the course of the swollen river.

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25 May 2023
Boron Stress on Citrus

Citrus Physiological and Molecular response to Boron Stresses

Since the essentiality of boron (B) to plant growth was reported nearly one century ago, the implication of B in physiological performance, productivity and quality of agricultural products, and the morphogenesis of apical meristem in plants has widely been studied. B stresses (B deficiency and toxicity), which lead to atrophy of canopy and deterioration of Citrus fruits, have long been discovered in citrus orchards. This paper reviews the research progress of B stresses on Citrus growth, photosynthesis, light use efficiency, nutrient absorption, organic acid metabolism, sugar metabolism and relocation, and antioxidant system. Moreover, the beneficial effects of B on plant stress tolerance and further research in this area were also discussed.

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