ASSESSING THE RISK OF PHYLLOXERA SURVIVAL DURING WHITE GRAPE PROCESSING
Dispersive stages of grape phylloxera, particularly first instars, can be inadvertently transferred on several potential vectors including post-harvest grape products such as juice. Fermentation of red grape juice for at least 72 h will kill phylloxera or filtering will prevent first instar transfer. White juice is processed differently to red juice, has different physiochemical properties and undergoes a range of treatments prior to filtering. Tartaric acid may be added to ensure pH is within a range of 3.0-3.4. At various stages in the white wine-making process sulphur dioxide is generally added, as either potassium or sodium metabisulphite. At maturity Baumé is usually between 10 and 12.5° depending on variety. Cool temperatures are generally used for white grapes with fermentation occurring at 10-16°C or lower, clarification occurring below 15°C and cold stabilization occurring at -4 to +2°C. The impact of pH, Baumé, white juice, sulphur dioxide and cold temperature on first instar phylloxera mortality was tested and results are described. In the absence of a food source first instar grape phylloxera survived up to 21 days in some treatments, including water at low temperature, which could also pose a quarantine risk.
Powell, K.S., Bruce , R.J. and Korosi, G.A. 2014. ASSESSING THE RISK OF PHYLLOXERA SURVIVAL DURING WHITE GRAPE PROCESSING. Acta Hort. (ISHS) 1045:49-58
phylloxera, quarantine, white juice, sulphur dioxide, cold temperature, Baumé, acidity