An ‘Insecticide test plot’ technique for early detection of pasture damage by grass grub,Costelytra zealandica(White) (Coleoptera: Scarabaeidae)

Abstract

A technique is described in which fensulfothion insecticide was applied in mid-late summer to plots of pasture for early detection of damage by grass grub (Costelytra zealandica). A trial which tested this technique on three sites near Riversdale, Southland in 1985 showed that there was an inverse relationship between grass grub density and the number of days before pasture damage became visible. The best time to establish the insecticide plot for early warning of potential grub damage was January. Further trials in 1986, where test plots were established in January over a range of sites with different grass grub densities, demonstrated that the technique would allow farmers to recognise a potential loss of pasture as a result of grass grub up to 6 weeks before they would otherwise have done so, and take remedial action or modify their pasture management to compensate.