Population growth of Dermatophagoides farinae Hughes (Acari: Epidermoptidae) suppressed by methoprene and hydroprene.

Insect growth regulators are synthetic chemicals that mimic the function of hormones that occur naturally in arthropods. Two such insect growth regulators, methoprene and hydroprene, were tested to determine effects on growth of laboratory populations of the American house dust mite, Dermatophagoides farinae Hughes. Adults and immature mites were treated with four concentrations of each chemical in contact and diet-incorporation bioassays. Data were collected after 30 and 90 d of exposure to the treatments. Both compounds significantly suppressed population growth when compared with acetone controls at concentrations of > or = 5%. Methoprene was more effective than hydroprene in diet-incorporation bioassays and was slightly more effective for the first 30 d of the contact assays. A second set of contact and diet-incorporation assays was done using one concentration (7.5%) of methoprene and hydroprene to determine the effect of these compounds on population dynamics of D. farinae. In this experiment, population numbers were evaluated at weekly intervals for 13 wk. The average number of mites in the untreated control population increased by more than 10 times the original inoculum during the experiment while the number of mites in the treated containers did not increase significantly. This trend was similar for both contact and diet-incorporation bioassays although the average number of mites per container was significantly higher when the treatments were incorporated in the house dust mite diet than when applied directly to the substrate.