Action and pharmacokinetics of a novel insect growth regulator, halofenozide, in adult beetles of Aubeonymus mariaefranciscae and Leptinotarsa decemlineata

Topical application of halofenozide on adults of the Colorado potato beetle (CPB), Leptinotarsa decemlineata, and Aubeonymus mariaefranciscae (AMF) ex hibited its effects in a different way in the two coleopterans. In CPB, the fecundity was strongly affected, whereas the main effect in AMF was a dras tic decrease of the progeny survival. The rate of penetration of labeled ha lofenozide through the cuticle followed a similar pattern in CPB and AMF, w hereas the rate of excretion was much more rapid in AMF. The extremely slow excretion of the product in CPB suggested that this fact must contribute t o the prolonged action of halofenozide on fecundity at its highest dose of 20 mu g per adult. Retention of halofenozide in the reproductive system of males of AMF and CPB was low, whereas high levels of radioactivity were rec overed in females (ovaries + eggs). Comparing females of both coleopterans, CBP retained a higher amount than AMF. Moreover, treated CPB adults showed a rapid cessation of oviposition due to distorted ovaries, detrimental ooc yte growth, and loss of oviposition due to the fact that yolk protein synth esis and/or incorporation into eggs was reduced. In AMF, the development of the progeny was strongly affected, and more than 80% of first-instar larva e died after egg hatching in the first 25 days after the treatment, due to premature molting and inhibition of ecdysis. Cross sections of intoxicated first larval instars of AMF originating from adults that were topically tre ated with halofenozide showed the presence of a double cuticle and these la rvae could not shed the old cuticle. Arch. Insect Biochem. Physiol. 41:201- 213, 1999. (C) 1999 Wiley-Liss, Inc.