The adult of this grub is a beetle which is commonly called the grass-grub beetle or the brown beetle. This species is the most serious insect pest in New Zealand. The larvae feed on roots of grasses. Before Europeans modified the New Zealand environment by changing large tracts of land to pasture land of exotic grasses, the grass grub lived on the roots of native grasses, but has now successfully adapted itself to the introduced grasses and is capable of destroying them. It occurs throughout New Zealand, and all the pasture lands in the country could be destroyed or seriously damaged by the ravages of this insect. Control measures are adequate, however, and good results are being obtained by the application of insecticides to the pastures. There is one generation per year. Larvae hatch from December to March and grubs are actively feeding in the soil from this time until the following September. Adults occur from October to January. Adult beetles are pest insects in their own right because they are phytophagous and eat the foliage of many crops. They fly at dusk and early evening, and populations can be so large that serious defoliation of seedling crops and apple trees, etc., can occur.
by Roy Alexander Harrison, D.SC., Senior Lecturer in Agricultural Zoology, Lincoln Agricultural College.