Summary of research by Minette Havenga| Ph.D. Genetics, MSc. Plant Pathology
Only a few sexual structures (chasmothecia) were observed in 1996-1999 in Stellenbosch. Since 2015, high numbers of chasmothecia are common on leaves at the later stages of the growing season in Western Cape vineyards. Asexual and sexual reproduction require different conditions, yet the primary inoculum for the infection is unknown. The biology and pathology of this fungus must be investigated to be able to understand what strategies can be implemented to improve the efficacy of management practices and subsequently reduce the number of fungicide applications. These include the role of post-harvest spray application on the reduction of inoculum source, the role of leaf litter and level of reduced fungicide sensitivity in different vineyards in order to effectively control the pathogen.
- Table and wine vineyards in Western Cape and raisin vineyards in Northern Cape are being surveyed to understand the geographical spread of the sexual state in South African vineyards. Symptomatic plant material including leaves, bark and bunches are sampled or sent in by other researchers or consultants from January until leaf fall. Please contact us if you have disease plant material that we can survey in this time.
- To get a better understanding of the life cycle, we are currently monitoring four vineyards in main wine and table grape areas in the Western Cape to determine the time of chasmothecia formation, when it matures, washes down to the bark and when spores get released. Additionally, the role of leaf litter as a potential source of inoculum for overwintering structures are also assessed.
- To understand the potential effect of a post-harvest spray application, we sample from vineyards on the day of application and two weeks after application to assess the effect on chasmothecia and its viability after treatment and the subsequent reduction in inoculum. If you are applying any treatment after grapes have been harvested and before leaf fall, please contact us.