A NOVEL TECHNIQUE FOR THE ELIMINATION OF POPULATIONS OF THE ORIENTAL COCKROACH, BLATTA ORIENTALIS L. (DICTYOPTERA: BLATTIDAE) USING (S)-HYDROPRENE DELIVERED FROM SIMPLE POINT SOURCES

Abstract:
Two mixed-age (semi-natural) populations of the Oriental cockroach Blatta orientalis were established in identical artificial domestic environments contained in steel freight containers. Each population was allowed a 10 week period of acclimation, during which the populations were monitored using Roatel traps. Subsequently, one population was treated with two point sources (filter papers) impregnated with 750mg of the insect juvenile hormone analogue S-hydroprene and 150mg of the anti-oxidant butylated hydroxy toluene (BHT). The other (control) population was exposed to point sources impregnated with BHT only. Each source was suspended from the ceiling under a cockroach-proof guard to ensure that physical contact with cockroaches could not occur. Treatments were repeated at six monthly intervals throughout the experiment. Changes in these populations were monitored for approximately two years by trapping every two weeks with live catch Roatel traps. On each occasion, trapped cockroaches were counted, the sexes of adults determined, and adults were examined for external deformities. Trapped nymphs were assigned to 1 of 3 arbitrary size categories (small, medium or large). Subsequently all trapped insects were released back into their respective containers. In addition, at monthly intervals, 20 adult females were randomly selected from the trapped insects and confined with several trapped males until ten oothecae had been produced. The viability and numbers of nymphs emerging from these oothecae was recorded. During the first 5 months of the experiment both populations showed a general increase. Subsequently, the control population increased substantially and then remained high for the duration of the experiment. After an initial small increase, the population in the hydroprene treated environment gradually declined and was eliminated after approximately 30 months. In the hydroprene treated container the percentage of adults exhibiting deformities exceeded 90% after 10 months and ootheca production was halted in this population at the same time. This inhibition of reproduction resulted in the eventual eradication of the population. These results suggest that hydroprene point sources could provide an extremely simple, and effective control technique for cockroaches infesting hospital, industrial, food manufacturing and domestic premises.