Dry heat as a disinfestation treatment against genetically diverse strains of grape phylloxera

Background and AimsGrape phylloxera, Daktulosphaira vitifoliae (Fitch), causes damage to ungrafted European grapevine, Vitis vinifera L. worldwide. In Australia, 83 phylloxera genetic strains exist in distinct zones and the primary management strategy is quarantine. While moving viticultural machinery, particularly harvesters from a phylloxera infested zone, dry heat treatment at 40 and 45 degrees C for 75 and 120min, respectively, is recommended. Methods and ResultsFirst instars of six root-feeding phylloxera, G1, G4, G7, G19, G20 and G30, were subjected to dry heat treatment at 22, 35, 40 and 45 degrees C for 75, 90 and 120min. For G20 and G30, first instars were subjected to 40 degrees C for 135min in a separate treatment. Across the six phylloxera genetic strains, no phylloxera survived treatment at 45 degrees C for 75min. First instars of G1, G4, G7, G19 phylloxera did not survive treatment at 40 degrees C for 120min. For G20 and G30 phylloxera, however, 100% mortality at 40 degrees C was achieved only when time of treatment was increased to 135min. The development of surviving phylloxera on excised V. vinifera cv. Chardonnay roots was influenced by the temperature of the dry heat treatment. ConclusionsResults validated the effectiveness of dry heat disinfestation protocol of 45 degrees C for 75min across diverse phylloxera genetic strains. The alternative protocol of 40 degrees C for 120min was not effective across all phylloxera strains and a duration of 135min is recommended. Significance of the StudyThis study highlights the relative sensitivity of genetically diverse phylloxera to heat treatment and duration of exposure.