|Phorid flies, Pseudacteon spp. (Diptera: Phoridae), are one of many biological control agents of Solenopsis spp. (Hymenoptera: Formicidae) fire ants in their native South America. More than twenty species of phorid flies are known to parasitize fire ants, of which, five species (Pseudacteon cultellatus, Pseudacteon curvatus, Pseudacteon litoralis, Pseudacteon obtusus, and Pseudacteon tricuspis) have been released into Alabama. Three species, P. curvatus, P. litoralis, and P. tricuspis are currently established in Alabama and were the focus of this dissertation.
Diurnal flight patterns of P. curvatus, P. litoralis and P. tricuspis were monitored in Alabama in 2010, and again from 2012-2013. During the study periods, the Pseudacteon species were co-established. These data were compared to data collected in 2002, when both P. curvatus and P. tricuspis were established but were not yet inhabiting the same areas. Both P. curvatus and P. tricuspis were active mid-day. The data collected in this study provide evidence that P. curvatus may be more successful than P. tricuspis when the species are co-established.
Seasonal abundance of P. curvatus and P. tricuspis was monitored between 2012 and 2013. This study was important in order to determine any differences from the patterns observed in South America. By finding the highest periods of abundance, researchers will be able to target that time of year for future studies on Pseudacteon phorid flies. A total of 7,284 P. curvatus individuals were collected during this study.
Pseudacteon curvatus was most abundant between June and August of 2012. Pseudacteon tricuspis was found only in June and September of 2012, and a total 23 P. tricuspis individuals were collected over these dates.
Alabama is the only state where P. litoralis is established, but it is only found in high numbers in a remote location of Wilcox County. The location of this species makes it difficult to study without significant funding. In order to monitor the outward spread of this species, two new trapping methods were tested against the currently used method. If successful, these new methods would allow for data to be collected in a more efficient manner. The tray trapping method, which is the method currently used to collect for P. litoralis in the field, was more successful than both new trap types tested.
Percent parasitism data were collected between July and October 2013 in Alabama where P. curvatus and P. tricuspis were co-established. During this study, only P. curvatus were collected. A mean parasitism rate of 0.059% was observed for P. curvatus, which was similar to the observed rates in Florida when only P. tricuspis was established.
These studies provide important and unique observations of the interactions among Pseudacteon spp. once co-established in the United States. The data suggest that current protocols may need to be altered in order to increase the likelihood of success of the biological control program.