grass grub

A population of hedgehogs (Erinaceus europaeus L.) in pasture land in Canterbury was found to vary between less than four and eight per hectare. Feeding habits were studied through stomach contents and analysis of faeces. Grass grub beetles (Costelytra zealandica) and porina moths (Wiseana cervinta), both important pasture pests, were relatively important food items. Estimates of the number of grass grubs eaten in relation to their density and that of hedgehogs in pastures show that hedgehogs are potentially capable of consuming 10-40 percent of adult populations.

Two of New Zealand's most important insect pests, grass grub and porina, are endemic species which have successfully colonised improved pastures. Population densities of these insects within this new environment are far greater than in the native plant systems in which they evolved. Within these high populations diseases have flourished, and high numbers of diseases are recorded from each of these pests. These include bacteria, fungi, nematodes, viruses and protozoa.

Withdrawal of the use of cheap, persistent organochlorine insecticides in New Zealand pastures has shifted the emphasis of insect pest control to non-chemical methods during the last 10-15 years.