Effects of a Juvenoid Pyriproxyfen on Reproductive Organ Development and Reproduction in German Cockroach (dictyoptera: Blattellidae) H. Fathpour, A. Noori, and B. Zeinali

The German cockroach, Blattella germanica, is one of the most common pest species, and is a carrier of many pathogen and allergen factors in humans. Thus, regarding public health, the control of this insect is quite important. Dietary use of hormone analogues, especially juvenoids which disrupt reproductive organ development, is a relatively new method to control cockroaches. In this study, the effect of dietary juvenoid pyriproxyfen was investigated on these insects. The control groups received a regular diet with no juvenoid and each of the treatment groups received 10, 30, 50, 100, or 300 ppm of pyriproxyfen in their diets, respectively. For each dose, 15 fifth-instar nymphs were used and the experiment was replicated three times. Each of the experimental repeats had a separate control group. The treatment period was 14 days, then the insects were fed with a regular diet until they emerged into an adult. At this stage, the treated adults were kept with an untreated opposite sex until the formation of the first egg capsule. Use of pyriproxyfen was found to be effective in inducing abnormalities in wing formation such as divergent, curly wing and giant nymphs. Furthermore, dietary use of this juvenoid caused the sterility of the insects due to incomplete development of the internal reproductive organs. Various morphologic abnormalities like deformation and degeneration were observed in the ovaries and accessory glands of sterile insects. Histological investigation of testis and ovaries in infertile insects indicated a degeneration of ovarian follicle cells, defective vitellogenesis, hypertrophy of testis walls, spermatogenesis disorder and a decrease in the numbers of spermatocyts and spermatozoa. The external genitalia of the sterile insects in both sexes were not significantly altered compared with the controls.