Towards greener pastures—Pathogens and pasture pests

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. Diseases have been frequently associated with population collapses in both grass grub and porina, and the role of diseases in natural population regulation is discussed. Insect diseases can also be applied artificially and can have a useful role in pest management.