Directorate of Rice Research, Rajendranagar, Hyderabad-500 030, Andhra Pradesh.
Nrem oil spray adversely affected growth of first instar nymphs of brown plantho-pper Nilaparvata lugens (BPH). But the residual effect was relatively poor. Neem oil exhibited moderate concentrption dependent adverse effect on growth and survival of eight day old BPH nymphs and their progeny. Nrem oil spray showed oviposition deterring effect against BPH at 12% or higher concentration but the egg production was not significantly altered even at 50% concentration. Neem oil spray even at 1% concentration showed growth disruptant effects against first instar nymphs of green leafhopper Nephotettix virescens (GLH) while 25% or higher concentrations were required for adverse effect on egg production. The toxicity of monocrotophos was significantly increased by neem oil against BPH but not so against GLH. Field studies indicated poor efficacy 01 neem oil against whorl maggot Hydrellia philippina, rice hispa Dicladispa armigera, stem borer Scirpophuga incertulas and gall midge Orseolia oryzae.
