AbstractA field study was performed in southern Alberta, Canada, to assess the native wasp, Trichomalopsis sarcophagae (Gahan), as a potential biocontrol agent for house fly, Musca domestica L., and stable fly, Stomoxys calcitrans (L.). The wasp was readily reared in large numbers, which allowed for the cumulative release of an estimated 4.63 million wasps into three commercial feedlots during the 2-year study. Each of several releases predictably and repeatedly enhanced parasitism of sentinel house fly pupae, whereas parasitism remained low in three paired control feedlots where wasps were not released. Releases every 2nd week had a disproportionately greater effect than releases every 2nd month. In 1998, 1.2 million wasps were released into treatment feedlots resulting in the recovery of 3 952 T. sarcophagae from 31 500 sentinel pupae (0.13 wasps/pupa). In 1999, 3.43 million wasps were released into treatment feedlots, with the recovery of 37 763 wasps from 47 720 sentinel pupae (0.79 wasps/pupa). Hence, a 2.8-fold increase in the number of wasps released in 1999 resulted in a 6.1-fold increase in the recovery of wasps. This result supports industry recommendations of regular, repeated releases of wasps every 2nd or 4th week versus one or infrequent releases throughout the summer. There was no evidence that releases augmented overwintering populations of the wasp in subsequent years. These results provide proof-of-concept for the mass-rearing and release of T. sarcophagae as an inundative biocontrol agent for the control of pest flies in cattle confinements. Further studies will be required to assess the effect of T. sarcophagae releases on natural populations of pest flies.
Poultry Litter Ash Rate and Placement Affect Phosphorus Dissolution in a Horticultural Substrate1