Host Plant Quality Factors That Influence the Growth and Development of Oxyops vitiosa, a Biological Control Agent of Melaleuca quinquenervia

The Australian weevil Oxyops vitiosa was released in 1997 in Florida as a biological control agent of Melaleuca quinquenervia. The larvae of this agent are flush-feeders, found only on the growing tips of their host. Knowledge of this restriction to feeding on the growing tips and other nutritional requirements may assist in the establishment and dispersal of this species. Therefore, O. vitiosa survival was assessed when neonates were fed M. quinquenervia leaves from branches that had dormant buds or emerging bud leaves. Additionally, the influence of leaf quality from different sites and within sites was determined by the feeding of neonates emerging bud leaves collected at three sites and from three leaf qualities (poor, intermediate, and high). Within-site leaf qualities were described in the field by leaf color and in the laboratory by percentage dry mass and nitrogen. Larval survival was lowest when fed leaves from branches that had dormant buds. Associated with this low survival were high leaf toughness and percentage dry mass. When larvae were fed emerging bud leaves, most of the variation in larval survival and performance was attributed to differences in within-site plant quality. Generally, the highest-quality leaves had relatively low percentage dry mass and high percentage nitrogen. Larval survival generally decreased when fed the poor-quality leaves, and in one site, the intermediate-quality leaves. Larvae required less time to develop to adults when fed the high-quality leaves. Development time increased in females but not in males when the larvae were fed the poor-quality leaves. Adult biomass of both females and males generally increased when the larvae were fed the high-quality leaves from two of the three sites. The results indicate that the larvae of O. vitiosa are restricted to feeding on flush foliage with low toughness. Additionally, variations in foliar percentage dry mass and nitrogen influence larval survival and performance. This knowledge benefited the development of mass-production nursery sites and the selection of suitable release sites, which facilitated the establishment of this biological control agent.