Infection of Anastrepha ludens (Diptera: Tephritidae) larvae by Heterorhabditis bacteriophora (Rhabditida: Heterorhabditidae) under laboratory and field conditions

Laboratory and field experiments were performed to determine the efficiency of the entomopathogenic nematode Heterorhabditis bacteriophora against third instar larvae of the tephritid fruit fly Anastrepha ludens. Infection was affected by low (6%) and high ( 12 - 24%) soil moisture; the highest prevalence of infection was observed at 9% moisture. LC50 values were estimated under laboratory conditions at densities of 0.16, 0.26 and 0.64 larvae/cm(3) of sand in containers of different depths ( 2, 5 and 8 cm) at 10% moisture, and larval ages ( third instar, early versus late stadium). Third instar A. ludens were significantly more susceptible to infection early in the stadium than late in the stadium, irrespective of host density (LC50 similar to 15 infective juvenile nematodes/cm(2) soil surface). Infection of late stadium third instars was significantly reduced at low density. Application of 115 and 345 infective juvenile nematodes/ cm(2) ( representing one and three times the laboratory LC50 at the lowest host density, respectively), in experimental plots in a commercial mango orchard, resulted in 46.7% ( range of SE: 45.2 - 48.1) and 76.1% ( SE: 74.8 - 77.3) infection, respectively. We conclude that H. bacteriophora merits further study as a natural enemy of Anastrepha spp. in tropical regions of the Americas.