World-Wide Search For N.Z. Pasture Pests Parasites

Press, Volume CI, Issue 29728, 23 January 1962, Page 19

World-Wide Search For N.Z. Pasture Pests Parasites

~Th* Press" Special service

NELSON, January 22.

A world-wide search is being carried out for natural parasites to attack the two w’orst New Zealand pasture pests, grassgrub and oxycanus (porina).

Suitable parasites, according to Dr. W. Cottier, director of the entomology division of the Department of Scientific and Industrial Research, could eliminate the need for insecticides and remove the possibility of harmful residues in meat and dairy products.

But both grass grub and porina are native New Zealand species and appear to have no effective natural enemies in this country. Related species overseas, however. are attacked and some-

times largely controlled by parasites.

“The search is being carr.ed out with the aid of the Commonwealth Institute of Biological Control," said Mr B B Given, officer in charge of biological control at the division laboratories in Nelson.

“This institute, with headquarters in Ottawa, has stations in Pakistan, India, California, Switzerland and

the West Indies. An exploratory station in southern Chile is almost entirely supported by New Zealand. “Scientists from the institute who are looking for parasites for, say. grass grub will collect parasites from

related species around the world and submit them to us for trial.”

But insect parasites are usually very specific and can live on only one or two closely related species. Searching for suitable parasites for New Zealand native insects is thus rather a hit-or-miss business.

For grass grub and porina. most of the searching is in South America, where insects occur which are fairly similar to the unique New Zealand species.

For this reason all tests on parasites are made under very strict quarantine, although the possibility of their causing any harm other than to the species to be attacked is usually remote.

The institute is looking for parasites for other pests beside grass grub and porina. although these are of the most immediate economic importance. Parasites for the clover casebearer, a caterpillar attacking clover and reducing the seed yield enormously, have been found in Europe and sent to New Zealand for testing. The potato tuber moth and the Argentine stem weevil, two other pests of economic importance, may be eventually controlled by biological means if searches overseas are successful. Great care must be taken that any insects or diseases introduced in this project will not attaelt New- Zealand rosaceous fruit plants as well. Initial tests will be made overseas before introduction.