The management and financial implications of variable responses to grapevine leafroll disease

Grapevine leafroll-associated virus 3 (GLRaV-3) is a worldwide pathogen of Vitis negatively affecting wine production. In red berry cultivars grown in New Zealand, the foliar changes to GLRaV-3-infected vines inform decisions on vine removal (roguing). However, roguing does not always contain GLRaV-3 spread presence an insect vector like mealybug, Pseudococcus calceolariae. Virus incidence and mealybug abundance data collected annually over 7 years were modelled under differing scenarios ascertain support for roguing. simulated 1 ha vineyard planted 2500 mature Merlot vines, simulations 20 evaluated effectiveness roguing, ‘rogue + 2’ (concurrent symptomatic plus both within-row neighbouring vines), inefficient (50% rogued), ‘no-action’. The model used variable initial (0.4, 5, 10, 15 20%), low, median high densities (6, 26 75 mealybugs per 100 leaves, respectively). Roguing was optimal response GLRaV-3, independent incidence, but results density dependent. At low density, relative other responses tested, sustained lowest annual least need plant replacement estimated average costs loss income. densities, remained most favourable control less effective incurred higher. Thus, vineyards affected by achieving economic sustainability relies integrating efficient with management.