Field Colonization of the Melaleuca Snout Beetle (Oxyops vitiosa) in South Florida

The Australian melaleuca snout beetle, Oxyops vitiosa Pascoe, a biological control agent of Melaleuca quinquenervia (Cav.) S. T. Blake, was first released in south Florida during spring 1997. Field-emerged adults appeared 3 months later, which affirmed survival of pupae despite occasional flooding. Releases at 12 other locations totaled more than 1500 adults and 6700 larvae by June 1998. Populations established at nine sites in Dade, Broward, Lee, Collier, Palm Beach, and Glades Counties. Habitats with short hydroperiods, intermediate stages of melaleuca invasion, and dry winter conditions engendered field colony development, whereas releases failed at aquatic sites. Even small releases (60 adults) produced populations at favorable sites. Abundant young foliage facilitated establishment, whereas soil type seemed unimportant: colonies developed at typical “glades” sites characterized by organic soils and at pineland sites with sandy soils. Larvae predominated during October to May, coincident with flushes of plant growth. In contrast, only adults remained during summer, except at a site that was periodically mowed. The new growth induced by mowing supported a persistent year-round larval population. This demonstrated that population trends are influenced more by plant phenology than by climatic conditions, possibly reflecting adaptation to the nonseasonal climatic oscillations (El Niño) of Australia. Transect sampling estimated the population at more than 2000 adults and 22,000 larvae, 1 year after release of 3300 larvae. Numbers swelled to almost 80,000 adults and over 15,000 larvae by June 1999 and to nearly 83,000 adults and 137,000 larvae by January 2000. Weevils dispersed throughout the 8.1-ha site but remained concentrated near release plots during the first 18 months. Ease of establishment and slow dispersal suggests an optimal strategy of many small releases at carefully selected but widely dispersed sites. Adults and larvae were subsequently relocated to other areas, and O. vitiosa is now widely established in southern Florida.