Parasites For Pasture Pests

Press, Volume CVII, Issue 31542, 2 December 1967, Page 10

Parasites For Pasture Pests

yyiDESPREAD and Intensive investigations by a team of biologists in South America to find possible means of solving New Zealand’s grassgrub and porina caterpillar problems by the use of predators and parasites are described in a recent report of the Commonwealth Insttiute of Biological Control.

The institute to part of the Commonwealth Agricultural Bureaux, of which New Zealand is a member, and the institute gave special attention to New Zealand’s two major pasture insect pests after the recommendation by New Zealand of such a project and the allocation of special additional funds, above New Zealand’s normal membership contribution, to promote the investigations. Interest in biological control of grassgrub and porina in New Zealand has been enhanced by the considerable increase in the pests’ depredations in the last season, particularly in Canterbury and Maryborough; by the increasing evidence of the insects’ developing resistance to D.D.T.; and by the ever-pre-sent risks, with chemical control,, of residues in produce, •nd the consequent strict control of the formulations used and the methods and times of application.

South America seemed to be a promising area for the search for an answer to New Zealand’s pasture insect pest problems because of the similar largely temperate southern hemisphere climate of its major pastoral countries such as the Argentine. Patagonia, and Chile, and because of the incidence there of somewhat similar soil-inhabiting insects suspected to be subject to parasite predators. Allocation of special scientific staff to intensify investigations in South America has made possible widespread field collection and study of pasture insect pests and their predators and parasites, and the institute’s principal laboratory at Trinidad is conveniently placed for co-opera-tion in the work. Close liaison has been established between the laboratory and headquarters of the Entomology Division of the Department of Scientific and Industrial Research at Nelson, and there is a regular interchange by air freight of promising material from South America for testing and controlled release in New Zealand, and of grassgrub and porina lavae for testing in Trinidad. .< In the last two yars some

60,000 insects of four species parasitising related pest species in South America have been introduced to New Zealand.

Intensification of investigation of the possibilities of the pests’ control by disease organisms and of the introduction and evaluation of potential parasites and predators was a principal recommendation adopted by the Government and announced by the Minister of Agriculture and Science, Mr Taiboys, after recent representations by the Departments of Agriculture and Scientific and Industrial Research on combatting the increasing threat of the pests to primary production. “Though we have had no success with the South American introductions yet,” said Mr I L. Baumgart, Assistant Director-General of the Department of Scientific and Industrial Research, who is New Zealand's liaison officer to the Commonwealth Agricultural Bureaux, “our support of the intensive work by this special team of biologists there has undoubtedly been worth while, as will be our intensified attention to the ecology and biology of the pesto by our Entomology IM vision.

“The division is working in the closest co-operation with the investigators in the field in South America and with the laboratory in Trinidad, so that there is a growing fund of knowledge of what our problems and requirements are and' what are potentially likely fields of inquiry in South America. The recent report shows how rapidly investigations have been intensified and how , widespread they are. and some promising developments are recommended for further testing. “Any appreciable degree of biological control of our major pasture insect pests that we eould achieve would be a tremendous boon,” said Mr Baumgart. “Present ehemieai methods of control are an appreciable part of farm costs in many districts, and if control methods are inefficient or ineffective, loss of production can be heavy, and in some seasons disastrous.

“Biological control of pests has been studied by our entomologists for many years, and we have had some successes, such as the introduction of parasites against the white butterfly, the diamondbacked moth, the oak leaf miner and the woojfry aphis.

However, it would be unwise to expect spectacular or early success with control of our pasture pests which present special problems, since they are native insects. Painstaking investigations and exhaustive tests are inseparable from such projects. Successes are not frequent, but they can be spectacular.

“The rate at which the special team in South America is accumulating knowledge likely to be pertinent to our problems, and the range of testing developed between our laboratories and theirs, cannot do other than enhance our prospects of a biological solution, if one exists.”