In plant disease control, the use of very effective aqueous remedies (i.e. fungicides, biocontrol agents, GRAS chemicals, etc.) sometimes yield disappointing results whereby growers suffer economic losses. In these cases, disease control failure is often attributed to insufficient application of the remedy. In this research focus area, various conventional and novel application technologies are evaluated and optimised in citrus orchards and packhouses in order to ensure biologically effective residue loading onto susceptible plant parts, without exceeding allowable maximum residue levels. Concomitant aims involve addressing cost and time efficiency aspects of application methods, whereby production and environmental costs are directly influenced. The methodology employed involves a proprietary deposition assessment protocol using fluorometry, digital photography and image analyses, as well as residue analysis and biological efficacy tests.
Citrus Black Spot (CBS) is a cosmetic disease of citrus fruit. However, its causal organism, Phyllosticta citricarpa, is regarded as a quarantine organism in certain export markets. The South African citrus industry is the second largest exporter of fresh citrus fruit in the world, and therefore CBS is an economically important disease given the market access implications it poses. In this research programme at USPP, the epidemiology of this disease is studied to understand and predict its behaviour under climatically diverse conditions. This will allow improved control programmes, but will also assist in ongoing market access deliberations. Additionally, population genetics of P. citricarpa will be studied on a global scale in order to ascertain the global movement of this organism and the relative importance of sexual and asexual reproduction under diverse climates.
Soilborne pathogens and pests of citrus such as Phytophthora, Pythiumand Fusarium spp. along with the citrus nematode, threatens sustainable long term citrus production. This research focus area studies preharvest management of these pathogens in the orchard and then also postharvest in the packhouse. Research include pathogen characterisation, evaluation and optimisation of current remedies and the development of novel management options using GRAS chemicals and novel technologies.
