Bulletin of Entomological Research

Table of Contents - 1999 - Volume 89, Issue 03  

Review Article

Indirect effects of ivermectin residues across trophic levels: Musca domestica (Diptera: Muscidae) and Muscidifurax zaraptor (Hymenoptera: Pteromalidae)

K.D. Floatea1 c1 and A.S. Foxa1

a1 Agriculture and Agri-Food Canada, Lethbridge Research Centre, PO Box 3000, Alberta, T1J 4B1, Canada

Abstract

Common house flies, Musca domestica Linnaeus, were reared to pupation with exposure to ivermectin, washed, and then exposed to parasitism by Muscidifurax zaraptor Kogan & Legner. Pupae exposed to ≥ 0.25 ppm ivermectin produced 63% fewer parasitoids than did control pupae. Pupae exposed to 0.01 ppm ivermectin produced 23% more parasitoids. Exposure to 0.10 ppm ivermectin had no detectable effect. Treatments did not affect the developmental time of male or female F1parasitoids. Treatments did not affect the production of adult F2 progeny by F1 females, nor the sex ratios of these offspring. This study documents an indirect effect of ivermectin residues across trophic levels. It identifies altered host quality as another mechanism by which faecal residues of ivermectin may affect insect activity in dung of treated cattle. The importance of this phenomenon under field conditions is undetermined.

(Accepted March 14 1999)

Correspondence:

c1 * Fax: (403) 382 3156 E-mail: floatek@em.agr.ca