Ishaaya, I., Dept. of Entomology, ARO, Volcani Center, Bet Dagan, Israel
Yablonski, S., Dept. of Entomology, ARO, Volcani Center, Bet Dagan, Israel
Ascher, K.R.S., Dept. of Toxicology, ARO, Volcani Center, Bet Dagan, Israel
Casida, J.E., Pesticide Chemistry and Toxicology Laboratory, Dept. of Entomological Sciences, University of California, Berkeley, CA, 94720, United States

Ethyl [2-(4-phenoxyphenoxy)ethyl] carbamate (RO 13-5223) at a dietary concentration of 100 mg kg-1 synergized the toxicity of the trans- and cis-isomers of permethrin and cypermethrin in inhibiting the growth (measured as gain in larval weight) of Tribolium castaneum and Musca domestica vicina. With both species the synergism factor for cis-cypermethrin with 100 mg kg-1 synergist was 1.5- to twofold for RO 13-5223 and about fourfold for piperonyl butoxide. Synergism was more pronounced with first instar than with fourth instar T. castaneum larvae. Methoprene was not a pyrethroid synergist with T. castaneum larvae, so the synergistic effect of RO 13-5223 appears to depend on its structural features and not its insect-growth-regulator activity. Joint application of RO 13-5223 and pyrethroids resulted in a dual effect on both T. castaneum and M. domestica: increased inhibition of larval growth due to pyrethroid synergism, and progeny suppression — expressed by larval and pupal mortality — due to RO 13-5223 juvenilizing activity. © 1984, Springer Science + Business Media B.V.. All rights reserved.