The toxic effects of neem extract and azadirachtin on the brown planthopper, Nilaparvata lugens (Stål) (BPH) (Homoptera: Delphacidae).
Extracts of neem (Azadirachta indica A. Juss) are used in the developing world for many purposes including management of agricultural insect pests. The effects of different neem extracts (aqueous (NSKEaq), ethanol (NSKEeth) and hexane (NSKEhex)) on mortality, survival and weight of the brown planthopper, Nilaparvata lugens (Stål) (BPH) (Homoptera: Delphacidae) third and fourth nymphal instars were investigated. When fed rice plants treated with neem derivatives in bioassays, the survival of BPH nymphs is affected. Comparisons were made with the pure neem limonoid, azadirachtin (AZA) to ascertain its role as a compound responsible for these effects. AZA was most potent in all experiments and produced almost 100% nymphal mortality at 0.5 ppm and higher concentrations. When higher concentrations were applied, the effects appeared shortly after treatment and mortality was higher. Many insects died after remaining inactive for several days or during prolonged moulting. At lower concentrations, if moulting was achieved, disturbed growth and abnormalities were then likely to occur in the moulting process. Nymphs that were chronically exposed to neem extract showed a reduction in weight (45-60%). The results clearly indicate the simple NSKE (aqueous, ethanolic or both), containing low concentrations of AZA, can be used effectively to inhibit the growth and survival of BPH.
Senthil Nathan
Sengottayan
S
Plant Environment Division, Honam Agricultural Research Institute (HARI), National Institute of Crop Science (NICS), Rural Development Administration (RDA), #381 Songhak-dong, Iksan, Chonbuk, 570-080, Republic of Korea. senthilkalaidr@hotmail.com
Choi
Man Young
MY
Paik
Chae Hoon
CH
Seo
Hong Yul
HY
Kim
Jae Duk
JD
Kang
Seok Min
SM
D000818:Animals; D031601:Azadirachta / Q000737:chemistry*; D006430:Hemiptera / Q000187:drug effects* / Q000254:growth & development; D036701:Limonins / Q000737:chemistry / Q000633:toxicity*; D015394:Molecular Structure; D009758:Nymph / Q000187:drug effects; D010936:Plant Extracts / Q000633:toxicity*
D036701:Limonins; D010936:Plant Extracts; C010329:azadirachtin