Crude extracts of root of the resistant pasture plants lucerne (Medicago sativa) and Lotus pedunculatus contain strong feeding deterrents for third instar Costelytra zealandica and Heteronychus arutor larvae. Purified saponins isolated from active crude lucerne root extract markedly reduce grass grub feeding and have an ED of 0.019%. Black beetle larvae are even more sensitive to the material. Separate and chemically distinct feeding deterrent fractions, active against the two insects, have been isolated from Lotus pedunculatus root. The role of feeding deterrents in mediating the non-preference of these insect pests for lucerne and Lotus is discussed.
