THE GRASS GRUB

Otago Daily Times, Issue 23894, 23 August 1939, Page 17

THE GRASS GRUB

DESTRUCTION OF PASTURE LAND RESEARCH DEPARTMENT'S ACTIVITY STATEMENT BY DR D. MILLER Dr D. Miller. Assistant Director of the Cawthron Institute and Director of the Division of Entomology of the Research Department at Nelson, who is at present in Dunedin in the course of his survey of the grass-grub and grass-caterpillar problems in Canterbury and Otago, made the following statement concerning his work to a Daily Times reporter last night. « " The Government and the Cawthron Institute are fully awake to the importance of the grass-grub and grasscaterpillar problem, and my souther visit is preliminary to a conference with the Director-gene-ral of Agriculture and the Acting-Sec-retary of the Research Department in Wellington on Thursday next. . " I consider that the grass-grubs and grass-caterpillars constitute what can be looked upon as the major entomological problem of this country since the foundations of our primary industries—that is pastures in relation to meat and wool—are in jeopardy in that many thousands of acres of pasture land (at least 80,000 in the Ashburton County alone) have been reduced to so much' rubbish by these two insects this season; and, most especially, at a critical period of the year. Other Insect Peats "By this, I do not wish to belittle in the least the almost equal influence of the diamond-back moth and the white butterfly upon the crops supplementary to the fattening of sheep; the latter insect, through the outstanding work of Mr J. Muggeridge, is under control from the farmers' point of view, while his current researches hold considerable hope of the former being eventually subjugated. "The grass grub and grass caterpillar problems are not for the entomologist alone. They involve many factors beyond his province and constitute one that demands team work—the association with entomologists of the fields staff of the Department of Agriculture, the staff of the Grasslands Division of the Plant Research Bureau, the field staff of the fertiliser industries, and the staff of those concerned with irrigation where that is being developed. Alljof these, I find, are deeply interestea in the matter.

" From the data at present available, I think that control, or at least a sufficient measure of relief to the unfortunate farmer, will be found eventually in a practicable modification of farm practice combined with the introduction and establishment of suitable parasites. On the first I cannot offer an opinion at the moment as that lies within the field of the pasture and farm ecologists and not in that of the entomologists. But in regard to the latter I might be permitted to offer an opinion; though I do not want to be swamped with letters from farmers asking the Cawthron Institute to send a supply of parasites for the immediate solution of the problem. We cannot wave the magic wand; the work is a big job and a long range problem. Parasites from Abroad "Both the grass-grubs and grasscaterpillars are insects native to New Zealand. Consequently one looks first to what parasites attack these insects in this country, and, finding none, looks overseas to regions that are biotically most closely related, and where similar pests occur. "With the grass-grubs we find that they have a free hand in New Zealand in that they are in no way subjugated by" any insect parasite. In the ,case of the grass-caterpillars we find one or two native parasites which obviously have but little controlling influence. "By looking further afield we find that certain channels of profitable inquiry open up to us in our next door neighbour, Tasmania, as well as in another Pacific biotic relative—the ChilePatagonian region. In Tasmania there exist similar grass-grub insects and a population of parasitic forms, unknown in New Zealand, that prey upon grassgrubs, but about which we in New Zealand know little at present. Tasmanian Aid "A somewhat similar insect to the grass-caterpillar occurs in Tasmania, but, like the caterpillar in New Zealand, it has a natural parasite that is ineffective—indeed, we nave sent "our parasites to the Commonwealth, and I fear with little effect. I have had word, however, from Dr J. Evans, the Tasmanian Government Entomologist, that he expects to visit New Zealand in November to discuss the several insect problems of interest to both countries. In the ChilePatagonian region one finds both grassgrubs and grass-caterpillars strangely similar to those of New Zealand During my expeditions to South America, I naturally gave some attention to the subject, and found that parasites existed there in the case of both types of insects. Being engaged at the time on the piri-piri (bidibidi) insects, however, I was not able to devote detailed attention to a study of the problem, but, nevertheless, secured sufficient data to show the possibilities of the situation in so far as New Zealand is concerned. These are matters that will be dealt with at the Wellington conference on Thursday. "I have to express my appreciation for assistance given me during my southern visit to Mr R. B. Tennent, director of the fields division of the Department of Agriculture, and to his staff; Mr McPherson, of Ashburton, and Mr Woodcock, fields superintendent at Dunedin. from whom I have secured data of incalculable value."