South African wheat producers should guard against over-application of fungicide, according to Dr Tarekegn Terefe, senior researcher at ARC-Small Grain, Bethlehem. The unnecessary use of fungicides can harm the environment and result in the emergence of fungicide-resistant strains. Farmers should also rotate between fungicides from different chemical groups, he writes.
Fungicides are widely used by South African wheat producers against foliar diseases. Common diseases treated with them include leaf rust, stripe rust, stem rust, powdery mildew, Septoria tritici blotch (STB) and Stagonospora nodorum blotch (SNB). Because genetically resistant cultivars may not be available, or because of new pathogen strains that break down resistance, fungicides will remain an important part of local wheat production.
For example, the emergence of new stripe rust races in 1998 and 2005 resulted in the outbreaks of this disease on previously resistant wheat cultivars such as Hugenoot and PAN 3191.
New stem rust races that are virulent on the resistance gene Sr31 were detected for the first time in South Africa in 2009 and 2017. Similarly, several leaf rust races that resulted in the breakdown of resistance genes such as Lr37 were identified locally in recent years.
MINIMISE FUNGICIDE USAGE
When previously resistant cultivars become susceptible due to the emergence of new races, fungicides are used to control these rust diseases.
Despite this, disease control options other than fungicides should be considered first. This includes the use of resistant cultivars. Fungicides should be used as a component of an integrated disease control strategy, not in lieu of it. Resistant cultivars have proved to be highly successful in combating foliar diseases; it is therefore wise to use these cultivars and cut down on fungicide use.
The cultivars commercially available in South Africa present varying levels of resistance to foliar diseases, especially wheat rusts, which can result in significant yield losses. Therefore, using two or more cultivars that have the highest levels of resistance to disease in a specific region will minimise the risk of disease outbreaks.
Esta historia es de la edición July 19, 2019 de Farmer's Weekly.
Comience su prueba gratuita de Magzter GOLD de 7 días para acceder a miles de historias premium seleccionadas y a más de 9,000 revistas y periódicos.
Ya eres suscriptor ? Conectar
Esta historia es de la edición July 19, 2019 de Farmer's Weekly.
Comience su prueba gratuita de Magzter GOLD de 7 días para acceder a miles de historias premium seleccionadas y a más de 9,000 revistas y periódicos.
Ya eres suscriptor? Conectar
Syngenta Seedcare celebrates a decade of innovation
Syngenta's ambition is to enable their customers' investments to grow in healthy soil from treated seeds to young plants through innovation and collaboration, writes Magda du Toit.
Agri workers shine at Western Cape awards
Lindie-Alet van Staden, a garden and olive orchard manager at L’Ormarins Wine Estate in Franschhoek, was crowned as the Western Cape Prestige Agri-Worker of 2024 at a gala event recently held near Paarl.
Small and large farmers recognised at grain awards
The annual Grain SA/Syngenta awards ceremony bears testimony to the quality of farmers in the grain industry.
Growing partnerships: Fedgroup's flexible and innovative approach
Janine Ryan spoke to Warren Winchester, general manager of impact investing at Fedgroup, about why the company became involved in agriculture, and what it offers farmers and their immediate communities.
Why fish farms fail, and how to avoid becoming a statistic
The popularity of launching fish farms is not matched by their success. Leslie Ter Morshuizen, owner of Aquaculture Solutions, explores the factors that cause most of these businesses to go under.
Where history and modernity meet in a luxurious setting
Brian Berkman kept his eyes peeled for ghosts in the oldest continuously run hotel in South Africa, but all he found was a fabulous two-night stay.
THE HITCHING POST
I'm a stylish elderly lady with a radiant glow and a good sense of humour that keeps me young at heart.
Cutworms: check the weeds on your fields!
Zunel van Eeden explains why understanding the ecological interplay between cutworms and weeds is crucial for effective pest management. Producers should disrupt the life cycle of cutworms to minimise crop damage.
Does high-density grazing mimic grazing patterns of game?
In their paper on high-density grazing in Southern Africa, professors Angelinus Franke and Elmarie Kotzé from the Department of Soil, Crop and Climate Sciences at the University of the Free State say high-density grazing systems may not accurately reflect natural ecosystems. Roelof Bezuidenhout reports.
Global grain outlook: 2024/25 marketing season
In its latest summer crops report, the Crop Estimates Committee says South African farmers intend to plant 4,47 million hectares of summer grains and oilseeds in the 2024/25 season, up 1% from the previous season. As South Africa exports maize and soya bean, Annelie Coleman reports on the latest trends in the international grain and oilseed markets, amid fluctuations in weather conditions and ongoing armed conflicts.
