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Tzaneen, South Africa

Blakey R.J.,Westfalia Technological Services
Postharvest Biology and Technology | Year: 2016

There is considerable financial incentive for avocado (Persea americana Mill.) growers in South Africa to begin harvest as soon as the minimum fruit maturity has been reached. The need to quickly process a large amount of samples for maturity determination pre- and postharvest using a user-friendly instrument provided motivation this study. ‘Fuerte’, ‘Hass’ and ‘Carmen®-Hass’ fruit were included in the calibration of the portable near-infrared spectrometer. The calibration included fruit from three seasons and the external validation included fruit from two further seasons. With this portable NIR spectrometer, it was not possible to develop a calibration model to accurately measure the maturity of avocado fruit non-destructively (‘Fuerte’: R2 = 0.654, RMSECV = 2.62, RPDCV = 1.23, ‘Hass’ and ‘Carmen®-Hass’: R2 = 0.400, RMSECV = 2.94, RPDCV = 0.79). A model incorporating all three cultivars, with the fruit peel removed, provided comparable results to the commercial method when using at least four fruit per sample (R2 = 0.732, RMSEP = 1.83, RPD = 1.14). The measurement of a single fruit took 30s, and could be conducted pre- or postharvest. © 2016 Elsevier B.V.

Carvalho C.P.,La Selva Research Center | Velasquez M.A.,La Selva Research Center | Van Rooyen Z.,Westfalia Technological Services
Agronomia Colombiana | Year: 2014

Colombia has become an important producer of ‘Hass’ avocado in the last three years; however, a minimum dry matter content has not been established as a maturity index for harvest. The aim of this study was to determine the correlation between oil percentage and dry matter content in order to establish a minimum harvest index for ‘Hass’ avocado fruits grown in Colombia. Samples were collected for maturity determinations over three years of ‘Hass’ avocado fruit cultivation from fifteen different orchards in the department of Antioquia in order to determine the dry matter and oil percentage of fruits throughout the season. A simple linear relationship between oil content and dry matter was thus established. The equations for all of the studied orchards presented a good correlation coefficient, ranging between 0.70 on the Cartucho orchard in the municipality of Retiro and 0.99 on the Gacamayas and Paraiso orchards in the municipality of Entrerrios and Retiro. Using the minimal oil standard of 11.2% as a reference, the orchards that were found to have a high dry matter percentage at harvest were Cartucho in Retiro (26%), followed by Piedras Blancas and Santa Cruz in the municipality of Venecia (25%); while the ‘Hass’ avocado fruit from the Cebadero orchard in Retiro, Coconi in the municipality of La Ceja and Guacamayas in Entrerrios reached this oil standard at 22% dry matter, which could be a commercial advantage. Based on these oil content results, a minimal dry matter index of 23.5% was proposed as a harvest maturity indicator for ‘Hass’ avocado grown in Colombia. This harvesting index will need to be refined over time and with the addition of samples from more regions and climatic data profiles. © 2014, Universidad Nacional de Colombia1. All rights reserved.

De Graaf J.,Westfalia Technological Services
Journal of Economic Entomology | Year: 2010

Sternochetus mangiferae (F.) (Coleoptera: Curculionidae) is a quarantine pest of mango, Mangifera indica L., in South Africa. The aim of the study was to test cultural and chemical control measures in a systems approach for risk mitigation of S. mangiferae in South Africa. A large-scale experiment, using a randomized block design with three replicates, was undertaken on 'Tommy Atkins' mangoes in South Africa. Five treatment combinations were applied over two seasons: 1) untreated control; 2) sanitation and physical removal of egg-infested fruit (P+S); 3) thiamethoxam, P+S; 4) thiamethoxam, fipronil, P+S; and 5) thiamethoxam, two fenthion applications, P+S. A weekly random sample of eight fruit from 40 trees per orchard was taken from 5 wk to harvest over two harvest periods. In total, 57,600 fruit were sampled. In a separate experiment, the same variety was used to test the efficacy of covering fruit with paper bags over one season in a completely randomized design. In both trials, all the pests were recorded from internal and external fruit inspections. In trial 1, results after the first season showed >98% control in the three chemical combination treatments. In the second season, treatment 2 provided 19% and treatment 3 99.9% control, whereas no fruit were infested with S. mangiferae in treatments 4 and 5. Trial two showed that fruit bagging significantly reduced S. mangiferae infestation. The data showed that a systems approach for S. mangiferae control in South Africa can be effective and that bagging can be an effective organic control option. © 2010 Entomological Society of America.

Trakunyingcharoen T.,Chiang Mai University | Cheewangkoon R.,Chiang Mai University | To-Anun C.,Chiang Mai University | Crous P.W.,Fungal Biodiversity Center | And 4 more authors.
Australasian Plant Pathology | Year: 2014

Fungal species of Botryosphaeriaceae have a cosmopolitan distribution and are important pathogens of a wide range of plant hosts. This study aims to use phylogenetic inference to review the geographical distribution of botryosphaeriacous species that have been associated with diseases of mango (Mangifera indica) globally. The phylogenetic analyses were performed based on the combined sequence datasets of the internal transcribed spacer (ITS) region of the nuclear rDNA and a partial region of the translation elongation factor 1-alpha (EF1-α) gene. The phylogenetic study revealed seven clades with distinct morphological characters from several countries, including Australia, Brazil, Egypt, Iran, Mali, Peru, South Africa, Taiwan and Thailand. Lasiodiplodia theobromae appears to be a dominant species on mango with the largest geographical distribution, whereas L. crassispora and Barriopsis iraniana have only been reported on mango in Brazil and Iran, respectively. These finding indicate that most of the species reported from mango are not restricted to specific geographical regions, although some genera appear to have a limited distribution. © 2014 Australasian Plant Pathology Society Inc.

Louw C.E.,Westfalia Technological Services
Acta Horticulturae | Year: 2013

Fruit fly larvae developing in mango fruit flesh affect marketability on local markets, while influencing producer-consumer relationships adversely. Fruit flies are also considered a phytosanitary pest, influencing the export of mangoes to foreign markets and limiting access to potential new markets. The key to successful control is effective monitoring, with early detection important to prevent the establishment of populations in the field, and to prevent unnecessary applications. Fruit flies in South Africa are usually monitored with a various fruit fly attractants and traps, monitoring the traps constantly to determine the first increase in population numbers, at which stage chemical control commences. In order to establish the accuracy of various traps and attractants commercially available in South Africa for predicting probable fruit infestation levels, Westfalia Technological Services conducted field trials in the 2007/2008 and 2008/2009 mango growing seasons. Traps were placed in the orchards prior to the first population build-up and monitored weekly, up to the time of the commercial harvesting date. Fruit were sampled with each assessment in order to determine fruit infestation levels. The results showed that the majority of traps were effective in attracting adult fruit flies, with population numbers increasing progressively towards the end of the mango season as more tree-ripening fruit were present in the orchard. None of the traps used, however, correlated strongly with fruit infestations and the traps were therefore considered ineffective in indicating probable fruit infestation levels. © ISHS 2013.

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