Ecological approaches to insect control: Control of pasture insects in New Zealand
- Entomology Division, D.S.I.R., Nelson
The control of noxious elements in the pasture insect complex has, with the rapid growth of world human population, assumed an often dangerous urgency. New Zealand, because of its great dependence on grassland farming, is less able than many countries to tolerate competition between insect and sheep or cow for available pasture. In our attempt to synthesise, largely from climax forest, a community favouring domestic livestock, we have compounded an environment eminently suited to two indigenous insects, the grass grub (Costelytra zealandica (White)) and the porina caterpillar (Wiseana spp.). It is axiomatic that the degree of stability of a community is proportional to its complexity: In the highly simplified environment of our exotic pastures, diversity has been reduced to a point where the population density of component species oscillates and where, when one or more of these component species is in conflict with our intentions, it becomes a pest.
I shall attempt to broadly review the extent of our knowledge and our ignorance of the biology and ecology of C. zealandica; for the deficiencies apparent in our study of this species are basic to an understanding of the other pasture pests with which we must contend.