Evaluating factors that influence the release efficiency of natural enemies for control of Brownbanded (Supella longipalpa (F.)) cockroaches

Abstract

Several factors that influence the ability of Anastatus tenuipes Bolivar y Pieltain and Compeiia merceti (Compere), two egg parasitoids of Brownbanded (Supella longipalpa (F.)) cockroaches, to find their host were evaluated in three Texas A&M University rooms. Simultaneous releases of A. tenuipes and C merceti produced parasitism levels of 48%, while releases of A. tenuipes produced parasitism levels of 43%. In contrast, releases of C merceti resulted in parasitism levels of only 9%. Moreover, A. tenuipes was able to locate 67% of the sentinel sites, whereas C merceti located only 24% of the sites. Increasing the number of parasitoids from 100 to 250 to 400 females per room significantly increased the parasitism levels of sentinel oothecae. When both A. tenuipes and C merceti were released at the highest density level, over 60% of the sentinel oothecae were parasitized. Releases of 250 and 400 A. tenuipes females produced parasitism levels of 44% and 52%, respectively. When 400 C merceti females were released, only 15% of the sentinel oothecae were parasitized. The effect of increasing the number of release locations within a room depended on the species. When 250 A. tenuipes females were released at 1, 2 or 4 locations within a room, the mean parasitism levels of sentinel oothecae were 57, 55 and 54%, respectively. When 250 C merceti females were released per room, parasitism levels were significantly higher when releases were made at four locations (33%) than when they were released at one location (24%). Two types of sentinel oothecae, live and freeze-killed, were used to monitor parasitoid releases. Neither species showed a preference for a specific host type; however, the number of progeny emerging from live and freeze- killed hosts differed. Significantly more A. tenuipes progeny emerged per ootheca from live parasitized hosts (6.7) than from freeze-killed parasitized hosts (0.6). The number of C merceti progeny that emerged per host from live (8.9) and freezekilled hosts (7.8) was similar. Results from this study indicate that A. tenuipes is better cockroach parasitoid than C merceti.