The ecology and control of mealybugs in Auckland vineyards

Abstract

Mealybugs have been recorded as pests on grapevines in New Zealand since the late nineteenth century. Control measures have included cultural techniques, releases of natural enemies, and applications of chemicals, but none has succeeded in giving adequate long term control of the insect. A questionnaire circulated to grape growers in the Auckland district in 1978 showed that mealybugs were still the predominant insect pest on grapevines, in the region, and so a study was initiated to determine possible control measures based on a knowledge of the insect in Auckland vineyards. The ecology of mealybugs was studied on vines at Kumeu and Riverheao, 30 km. to the north west of Auckland. Populations were found to develop through three generations per season on the foliage. Development of the first two generations were well synchronised by the rapid spring growth of the vine, but synchrony was lost in the third generation when the age structure of the mealybug population stabilised. Adult female mealybugs reproduced under the bark in the early part of the season but by Christmas there was sufficient shelter in fruit bunches and within the inner foliage canopy for reproduction to occur throughout the vine. Numbers of mealybugs on foliage were correlated with numbers on fruit, but the variation was too great to allow significant predictions of mealybug levels on fruit from numbers on leaves.