Insect Antifeedants And Growth Inhibitors From Azadirachta Indica And Plumbago Zeylanica

Abstract

Solvent extracts of dlfferent parts of the neem tree (Azadlrachta lndica A. 3uss)
\nwere bioassayed for thelr antlfeedant properties agalnst flrst- and thlrd-instar
\nlarvae of Mythimna reparata. Fraction 'C', obtalned from an ethanollc extract of
\nthe shade-drled neem seeds (Hyderabad, India) was the most effective phagodeterrent
\nunder glasshouse, laboratory and, to a 11mlted extent, fleld conditions.
\nFractlon 'C' was further purlfled to fractlon 'M', whlch was subjected to column
\nchromatography (silica gel) result~ng In IG fractions, AI-l to AI-14. Fractions
\nAI-9, AI-10 and AI-11 were found to be b~olog~calalyc tive, reduclng leaf feedlng
\nand larval weight consrderably. None of the treated larvae whlch fed on leaf
\ndlscs treated wlth the fractions and extracts 'C' and 'M' could pupate. The retentlon
\ntlme of the malor component of AI-10 on a p BONDAPAK C18 10 u, 3.9
\nmm ID, 30 cm column (hlgh performance liquid chromatography) was close to
\nthat of azadlrachtln. Spectral lnvestlgatlons revealed that this major component
\nof A1 1s dlfferent from the antifeedants reported earher from A, indica and Melia
\nazedarach. It has been des~gnated as vepaol (the Telugu name for neem IS vepa),
\nand some aspects of 11s structure are discussed. Studles relatlng to the effectiveness
\nof fraction 'G' on the oriental rmyworm, Mythrmna reparata, and other sorghum pests are presented.