Repellent and lethal effects of seven chemicals on house dust mites, Dermatophagoides farinae Hughes (Acari : Pyroglyphidae) and Tyrophagus putrescentiae (Schrank) (Acari : Acaridae)

Abstract

Repellent and lethal effects of 7 chemicals on house dust mites, Dermatophagoides farinae Hughes (=Df) and Tyrophagus putrescentiae (Schrank) (=Tp), were evaluated with mite-rearing culture and mite individuals. Papers, treated with phenyl salicylate and (1R, 2R, 4R)-born-2-yl 2-thiocyanoacetate (=IBTA) at a dosage of 0.05g(AI)/m^2,inhibited >80% of Df and Tp from creeping up from the mite-rearing culture. Benzyl benzoate and diethyltoluamide (=deet) at 0.5g/m^2 also indicated >80% repellent rates against 2 mite species. However, the repellent rates of fenitrothion for Tp and that of bis (2,3,3,3-tetrachloropropyl) ether for Df were less than 60% even at 5g/m^2. IBTA at 5g/m^2 demonstrated the longest residual activity, showing >90% repellent rates for 65 days. Fast-acting effect was evaluated by observations of mite individuals on the chemical dry film at a dosage of 0.002g/16(cm)^2. Benzyl benzoate, IBTA, deet for Df and deet for Tp immobilized >90% of the test mites within 30 min. From the symptoms and behavioral changes of the mites on the chemical dry film, the test chemicals were classified into knock down type and immobilizer type. It was found that benzyl benzoate, IBTA and deet immobilized the mites, but a few were knocked down. It was suggested that there were different intoxication mechanisms in the test chemicals.