(Stuff) - A South African professor specialising in plant research has congratulated the New Zealand wine industry for executing a world-first in developing an innovative strategy to deal with leafroll virus in vineyards. Vines infected by leafroll virus turn a reddish purple colour before their leaves roll down, producing smaller fruit clusters and a lower brix (sugar level) at harvest. The disease does not kill the vine, but it can be spread by infected nursery stock or mealybugs.