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.
Eriophyoid mites (erios for short) are the smallest of all mites, with adults around 0.5 mm long. Their small size makes it difficult to spot them in the field, even with a good hand lens. They are sporadic pests that cause serious damage during outbreaks. Usually, erios are found because of the symptoms they cause – bud deformation, rusting or galling, depending on the species. Some erio species live on plants without causing symptoms at all.
Citrus is the main fruit tree crop in the world and therefore has a tremendous economical, social and cultural impact in our society. In recent years, our knowledge on plant reproductive biology has increased considerably mostly because of the work developed in model plants. However, the information generated in these species cannot always be applied to citrus, predominantly because citrus is a perennial tree crop that exhibits a very peculiar and unusual reproductive biology.
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.
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.
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.
The goal of this research was to identify the role essential nutrients play in the physiology of tree crops, and then to apply the nutrient as a foliar fertilizer to stimulate a specific metabolic process at phenological stages when nutrient demand is high. This approach has proven successful. A single winter prebloom foliar application of nitrogen as low-biuret urea [0.16 kg N/tree (0.35 lb N/tree)] to 30-year-old ‘Washington’ navel orange (Citrus sinensis L. Osbeck) trees during flower initiation significantly increased yield and fruit number per tree for each of 3 consecutive years (P ≤ 0.05). The number of commercially valuable large size fruit also increased significantly with yield increases (r² = 0.88).
Summer Citrus from South Africa (SCSA) has entered its 25th shipping season with the first fruit arriving in the US towards the end of May.
Despite recent heavy rainfall in the Western Cape and in Citrusdal, where SCSA’s growers are primarily located, the group said it was reorganising after days without electricity, and a lack of access to citrus groves and some roads.
Despite the challenges and a minor setback with timing, SCSA promised that high-quality fruit was on the way weekly for the rest of the summer.