Recent heavy rainfall in the Western Cape has yielded both positive and negative outcomes for vineyards in the region.
Rainfall levels across Western Cape’s winegrowing areas varied, ranging from 79 mm in Paarl to 28 mm near Darling (refer to the rain distribution graph for specifics). This precipitation arrives following an exceptionally dry winter and spring, resulting in lower groundwater levels than usual.
Conrad Schutte, Vinpro’s Consultation Services Manager, explains, “Producers had to commence irrigation earlier and more frequently than usual to meet vineyard requirements. Frequent instances of load shedding have significantly impacted irrigation schedules, particularly in intensive irrigation zones, where vineyards cannot receive sufficient irrigation. The current vine growth phase involves berry cell division, making it susceptible to stress, particularly water stress, which detrimentally affects the process. This leads to smaller berry sizes and a corresponding decrease in total yield per hectare.”
The recent days’ rainfall has been a welcome relief for groundwater replenishment, alleviating pressure on irrigation timetables, and fostering berry growth and crop sizes. Additionally, the rainfall contributes to the rise of dam levels, enhancing irrigation potential for the remainder of the season.
Nevertheless, the significant rain also amplifies production risks, particularly the emergence of fungal diseases due to increased water presence, elevated humidity, and temperature.
Schutte notes, “Recent weather patterns, featuring rain followed by hot and humid conditions, have favored primary and secondary infections, notably powdery and downy mildew on vineyards. Most producers adhere to preventive fungicide spray protocols and should reapply these after the rain subsides and access to vineyards is restored. However, the elevated risk of infection while berries and bunches are drying requires monitoring, and the effectiveness of spraying programs can only be evaluated in the coming weeks.”
Isolated hailstorms in Paarl, Worcester, and Robertson have caused sporadic damage, impacting canopies and bunches, although it’s still early in the growing season. Appropriate treatment should allow damaged grapes on bunches to dry up with minimal consequences on the overall crop size. Reports of damage to vineyard infrastructure and facilities, including roads and buildings, have also surfaced and are currently under repair.
Schutte emphasizes, “The rain will stimulate continued vegetative growth in actively growing vines. In such cases, canopy management practices must be implemented to control shoot growth. Clearing fruit zones and breaking leaves for optimal lighting and airflow can aid ripening and assist in fungal disease control.”
