Contact and fumigant toxicity of oriental medicinal plant extracts against Dermanyssus gallinae (Acari: Dermanyssidae).

The acaricidal activity of methanolic extracts from 40 oriental medicinal plant species and a steam distillate of Cinnamomum camphora towards poultry house-collected adult Dermanyssus gallinae De Geer was examined using direct contact and vapour phase toxicity bioassays. Results were compared with those of 15 acaricides currently used. In filter paper contact toxicity bioassays using adult D. gallinae, C. camphora steam distillate (0.0051 mgcm(-2)) was the most toxic material, followed by extracts from Asarum sieboldii var. seoulens whole plant, Eugenia caryophyllata flower bud and Mentha arvensis var. piperascens whole plant (0.0063-0.0072 mgcm(-2)), based upon 24h LD(50) values. The acaricidal activity of these four plant preparations was almost comparable to that of profenofos (LD(50), 0.003 mgcm(-2)) but less effective than dichlorvos (LD(50), 0.0004 mgcm(-2)). The toxicity of Illicium verum fruit and Lysimachia davurica leaf extracts (0.09 mgcm(-2)) was almost comparable to that of benfuracarb, prothiofos, propoxur and fenthion (0.053-0.070mgcm(-2)). In vapour phase toxicity tests, these plant preparations were more effective in closed containers than in open ones, indicating that the mode of delivery of these plant extracts was largely a result of action in the vapour phase. Plants described herein merit further study as potential D. gallinae control agents.