Sodium arsenate has been the treatment for the xylem-limited fungal grapevines trunk disease (GTD) in Europe until its ban in 2003. Since then, many vineyards in Spain resorted to using the injection of fungicide and sealing of pruning or cutting wounds to mitigate the condition. As GTD is challenging to detect its early infection, there has never been an effective preventive measure until the symptoms occur, and often it is too late to prevent any loss in plant vigour and productivity. Some viticulturist resort to chipping open the trunk of the grapevine to investigate “suspected” trees, but it is a tedious, cost and time-consuming effort (photo Fig 1a, 1b, 1c).
In a two-season program in 2016 and 2017, a protocol combining OCC colloidal nutrient and hydrogen peroxide as a spray program was developed with the viticulturist to apply the mixture directly on the trunk of vines (photo Fig 2). Once after winter pruning, once after summer trimming. The colloidal nutrient was able to bring the oxygen molecule emitted from hydrogen peroxide and penetrate directly into the vascular system to contain the fungal pathogen.
This preventive measure has proven to be successful as no symptoms of GTD was detected in the subsequent seasons, and previously infected grapevines have recovered from the disease after one season of application (Fig 3).
The canopy is the first and most vulnerable infection area as wounds from cutting, and pruning occurs at the canopy. When infection occurs, it is also the most severely infected area.
Spray the entire canopy with OCC colloidal nutrients with 5% concentration of hydrogen peroxide or fungicide (with 30% reduction from label’s recommended dose) periodically would avoid infection, and allow the canopy to recover if infected.
Trunk & Roots
GTD is a disease that transmits through the vascular system of the plant. Hence a healthy vascular system is essential to minimise the risks of infection through the entire plant.
OCC colloidal nutrient can penetrate through the trunk and bark surface into the vascular system.
Spraying the entire trunk, in particular, the lower portion of the trunk and soil surrounding it will mitigate the disease in the rootstock as well.
OCC colloidal nutrient in combination with 5% hydrogen peroxide can mitigate harmful soil-borne fungal pathogens and nematodes, while not harming beneficial fungi such as Trichoderma sp. Hence, regular irrigation with the mixture will ensure root health and also prevent soil-borne diseases.