Programme leader: Dr Paul Fourie
Fungicide application technology
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
programme, 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
Epidemiology of Citrus Black Spot
Citrus Black Spot (CBS) is a cosmetic disease of citrus fruit.
However, its causal organism, Guignardia citricarpa, is
regarded as a quarantine organism in certain countries. 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 G. 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.
Gray-Lee Carelse - Pathogenicity and chlorine sensitivity of Pythium species associated with citrus nurseries in South Africa.
Soné Reens - Pathogenicity and fungicide sensitivity of Neucosmospora and Fusarium species associated with citrus in South Africa.
Tertia van Wyk - Implementation and validation of reduced volume agrochemical applications in the South African citrus industry using novel technology.
Lize van der Merwe - Evaluation of new postharvest fungicides for the control of Phytophthora brown rot.
Gideon van Zyl - The use of adjuvants to improve fungicide spray deposition and control of Alternaria brown spot in citrus.