Screening white clover for resistance to grass grub in a controlled environment

Abstract

Controlled environment conditions were used to compare growth of individual third instar grass grub (Costelytra zealandica) larvae on white clover (Trifolium repens) lines and genotypes. There were repeatable differences in weight gain of grass grub larvae between different white clover lines in one soil with the highest weight gains being on ‘Grasslands Kopu’ grown in Opiki humic silty clay loam. However, selection of genotypes supporting high or low grub weight gains and re‐screening them for grub weight gains was not successful. Root type had no effect on grub weight gain, but the differences in weight gain between two soil types was of comparable magnitude to that observed for line differences. Weight gain correlated negatively with feeding deterrent activity and positively with soluble sugar content of root extracts.

Keywords:

• Trifolium repens
• white clover
• Costelytra zealandica
• grass grub
• resistance
• variation
• controlled environment
• larval growth