Impacts of bioactivitses of extracts from yellow azalea, Rhododendron molle G.Don on larvae development of Ostrinia furnacalis.

Antifeeding, poisoning and growth inhibition properties of Rhodojaponin Ⅲ (Abbr. R Ⅲ) and ethyl acetate (EtOAc) extracts of flowers from yellow azalez, Rhododendron molle G.Don on the 3rd instar larvae of Ostrinia furnacalis Guenee were reported. The values of AFC 50 (median antifeeding concentration) of R Ⅲ and EtOAc extract were 77 02 and 384 30 mg/kg diet with column shaped diet method, but were 15 60 and 255 44 mg/kg diet with body weight method, respectively. After 4d treat\|ment with 2000 mg/kg R Ⅲ and 200 mg/kg EtOAc extract, 86 67% and 66 67% mortality were obtained, as well as 2 99 and 3 85d for LT 50 (lethal median time) on 15th day after treatment respectively. After 15d treatment with R Ⅲ and EtOAc extracts the vgalues of IC 50 (medium inhibitory growth concentration)were 9 30 and 39 64 mg/kg diet, respectively. The measure method and action characters of R Ⅲ and EtOAc extracts such as postingestive effects, were also discussed.