Biochemical activity of centipedegrass against fall armyworm larvae

Abstract

Centipedegrass,Eremochloa ophiuroides (Munro) Hack, severely inhibits growth of the fall armyworm larva,Spodoptera frugiperda (J.E. Smith). Fresh centipedegrass extracts and extract fractions were deposited on Celufil, incorporated into meridic-based diets and bioassayed against neonate larvae of the fall armyworm in the laboratory. The methanol extract (F₁) caused the greatest reduction in larval weight. When F₁, was partitioned between méthylene chloride and water, the activity was transferred to the water-soluble fraction (F₅), which, when further fractionated using preparative C-18 reverse-phase chromatography, yielded active F₇ and F₈ fractions. Gas chromatograph-mass spectrometry and high-pressure liquid chromatography (HPLC) showed F₇ to be 95% caffeoylquinic acids with chlorogenic acid as the major constituent. HPLC analysis of F₈ revealed maysin [2″-O- α-L-rhamnosyl-6-C-(6-deoxy-Xylo-hexos-4-ulosyl)luteolin] and other luteolin derivatives. Chlorogenic acid and other caffeoylquinic acids, maysin, and other luteolin derivatives are the major factors responsible for the antibiotic resistance of centipedegrass to larvae of the fall armyworm.