Toxicological effects of pyriproxyfen and chlorfluazuron (IGRs) on Monomorium pharaonsis (Hymenoptera: Formicidae) in laboratory and field

Abstract

The present study was examined the effect of certain IGRs (pyriproxyfen & chlorfluazuron) on the Pharaoh ant workers Monomorium pharaonis (L.). Artificial medium (peptone, glucose, and agar) was chosen according to palatability test, for trapping Pharaoh ant workers. Pharaoh ant samples were collected from three different areas (Abbassia, Heliopolis and Nasr-city) both indoors and outdoors, treated with different conc. of IGRs 0.1%, 0.5% and 1% for pyriproxyfen and 0.001%, 0.01% and 0.1% for chlorfluazuron both indoors and outdoors. The potential of insect growth regulators was estimated in natural nests (field), the percentage reduction in workers was determined for eight weeks after the treatment at interval of one week. Samples collected from Abbassia were more tolerant than those collected from the other two areas at low conc. of both IGRs (0.1% pyriproxyfen & 0.001% chlorfluazuron). While workers collected from Nasr-city were more susceptible than workers collected from Heliopolis and Abbassia at high conc. of both IGRs (1% pyriproxyfen & 0.1% chlorfluazuron). In comparing the two IGRs used in the same conc. (0.1%), it was found that chlorfluazuron was more effective than pyriproxyfen. The highest mortality (100%) was reached after about 8 – 10 days of treatment by chlorfluazuron, while it was reached after 16 – 22 days of treatment by pyriproxyfen in laboratory. In field tests, baits containing 1% pyriproxyfen, the percentage reduction of workers reach 85.5% after 8 weeks of treatment, while baits containing 0.1% chlorfluazuron, the percentages of reductions in workers was 95.2%.