Costelytra giveni

Scarabaeidae  : Melolonthinae

The bane of farmers in New Zealand. This native species has become well adapted to the exotic pastures on which our farming is based. During 1950- 1990 much research was done on its life history, population structure and its damage to pastures. Many insecticides were trialled and DDT became one of the main controlling chemicals. This was finally taken off the market in 1970's but its degradation products and those of other insectides (organophosphates etc) still lie in the soil and affect the quality of the meat of sheep and cattle. It was also used in horticulture. Now the damage by "the grassgrub" the larva of C. giveni is controlled by cropping and rotation methods, or just tolerated and its cost is absorbed within the economic system. Canterbury was particularly prone and lowland and highland farming is still affected by this beetle's presence. It has been argued that the distribution of this beetle has been extended by the replacement of native grassland with pastures and the combination may have displaced other species of Costelytra which have not been reported as causing damage. Those other species may suffer in conservation as they would be considered by most people as just another grass grub. This could easily happen as damage to plum trees in North Canterbury was blamed on the "grass grub" rather than the actual beetle, the very similar looking Odontria nitidula. This may well have been the case in other horticultural areas. Only a few South Island records are shown. It is abundant also in the North Island. It may be some time before the name change becomes normal usage by others. The name change was necessary due to a misidentification many years ago.

Text updated: 10/04/2017