GRASS GRUB CONTROL

Abstract

Farmers throughout New Zealand agree that grass grubs, or the larvae of Odontria zealandica, are the most serious insect pests of pasture. Though damage is not conspicuous every year in established pasture, there is usually a certain amount of annual thinning out of valuable fodder plants and their replacement by weeds such as plantain, dandelion, mouseeared chickweed, and weed grasses such as sweet vernal and hair grass. It is difficult to estimate losses involved in this way except by close inspection of pastures or by a fall in farm returns. For example, one dairy farm in the Waikato produced over 80001b. less butterfat this :year than last, and yet it was only after a careful mspection that it was found that these pastures-though they looked uniform from a distance- had deteriorated by approximately one third. Though no definite sequence of grass grub damage can be predicted, it is common for an infestation to build up over a period ranging from 1 to 8 years, with damage becoming progressively worse from an original patchy effect till the pasture is more or less uniformly infested.