Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 21, 1997
Publication Date: N/A
Interpretive Summary: House flies and stable flies are often produced in large numbers on live- stock and poultry farms. Fly outbreaks reduce farm profitability, cause public health and legal concerns for farmers, and are a source of socio- logical friction at the rural-urban interface. Traditional fly control using insecticides is no longer effective and runs counter to public demand dto reduce insecticide use in agriculture. Non-insecticidal fly control methods are needed to develop integrated fly control programs. Parasitic wasps that attack fly pupae currently hold the greatest promise as practi- cal fly-control tools. Many species of these parasites occur outside the U.S. but we lack objective criteria for evaluating whether or not to import them. This study was part of a larger project to develop a set of testing standards so that knowledge-based decisions can be made about importation and release of foreign species of fly parasites. Temperature effects on survival and development times of a Brazilian parasitoid, Spalangia gemina were compared with the two most important native species, Spalangia camer- oni and Muscidifurax raptor. These tests were done under constant and vari- able temperature conditions. S. gemina was very similar to S. cameroni, although S. cameroni was more tolerant of temperature extremes. Two mathe- matical models of development rates were compared; a simple degree-day model and a non-linear biophysical model. The biophysical model was more precise, but the simple degree-day model was satisfactory for predicting development times under realistic temperature conditions. S. gemina is pre- dicted to perform well in enclosed poultry facilities throughout the year, and in outdoor situations such as feedlots in early summer and fall.
Technical Abstract: Development rates were determined for three pteromalid parasitoids of house flies under constant temperatures from 15 to 35 degrees C. Muscidifurax raptor Girault and Sanders was the fastest developing species, with females completing development in 13.8 days at 32.5 degrees C to 66.5 days at 15 degrees C. Spalangia gemina Boucek females completed development in 20.8 days at 30.0 degrees C to 161 days at 15.0 degrees C, whereas S. cameroni Perkins females completed development in 20.6 days at 30.0 degrees C to 155.5 days at 15.0 degees C. Male development times were 90.3% those of females for S. gemina, and 92.7 and 88.6% those of females for S. cameroni and M. raptor, respectively. Parasitoid survival was very low at 35 degrees C for all species, and no Spalangia survived constant exposure to 15 degrees C. Exposure to these lethal temperatures for shorter periods indicated that the parasitoids can tolerate them well under conditions more typical of the field. Development rates were modelled using the biophysical algorithm of Sharpe and DeMichele and a degree-day model. These models were tested for their ability to predict development under fluctuating conditions (24-36 degrees C). Neither model was superior for all three species because of interspecific differences in the parasitoids' responses to high temperatures. Agreement between predicted and observed develop[ment times for all three species was achieved by small empirical adjustments of a key parameter in the biophysical model.