D.D.T. BAN Passing Of Old Friend

Press, Volume CIX, Issue 32221, 13 February 1970, Page 8

D.D.T. BAN Passing Of Old Friend

Tn the removal of D.D.T. from the farming scene in New Zealand at the end of June this year, farmers in Canterbury might well feel that they are losing an old friend.

People have differing views about D.D.T. In recent years even some farmers have been let down by it as there has been an increasing incidence of grubs that have shown resistance to the old insecticide, and in earlier days too it did not always give the lengthy period of protection claimed for it. sometimes because of poor mixing of the insecticide with superphosphate. But for all of that D.D.T has contributed materially to Canterbury's farming prosperity in the last 26 years and authoritative speakers in looking at the upsurge in production on Canterbury farmlands in recent years have frequently acknowledged the part that D.D.T. has played in this process.

Back in 1946. in discussing the grass grub and porina problem in farmlands, it was noted in the farm pages of this newspaper that a detailed survey of the damage down by grass grub had been made about five years earlier by A. H. Flay and H. E. Garrett and published in the “Journal of Science and Technology ' Their estimate was that grass grub cost farmers about £600,000 a year in Canterbury alone and that on a medium land farm the cost was about 6s an acre a year over a seven-year cycle.

Damage in the autumn and winter of 1952 was put at £4m in Lincoln College s “Annual Review.” In 1965. Mr J. M. Kelsey, officer in charge of the Lincoln sub-station of the Entomology Division of the Department of Scientific and Industrial Research, was quoted in “The Press” as saying that if grass grub could be eliminated from sown New Zealand pasture lands it would be worth an extra £32m in extra agricultural production. Speaking at the same time the director of Mr Kelsey's division, Dr J. M Hoy, said that the high level of production from New Zealand pasture lands at that time

was linked with a high standard of grass grub control and the long term effects of a reduction in D.D.T. use on production could be considerable.

This was in the yeai' after an earlier move restricting the use of D.D.T. At the end of June, 1964, it was no longer permissible to use D.D.T. in dust forms and these were replaced by prills or pelleted form of D.D.T. super. There was some relaxation of this ruling in 1967 when after the most serious attack of pasture pests in years in the province use of oiled wet mix D.D.T. super was allowed subject to permit and pending the introduction of granular D.D.T super. An early reference to the use of D.b.T. against grass grub and porina caterpillar, is contained in “The Press" of July 3, 1948, when it was

quoted from the annual re port of the Entomology Division that investigation of all aspects of the grass grub problem in New Zealand was a major long term activity of the division. Reference was made to the work being done at the special entomological substation at Ashburton and it was reported that experiments with insecticides had been undertaken against grubs and beetles. In respect of the former no final conclusions had been reached, but it had been shown that a very marked control of beetles could be obtained. For example, in a field experiment carried out in conjunction with the Department of Agriculture, DDT. had been used with good results. D.D.T. had also been verv effective with porina

A little later Mr Kelsey, as officer-in-charge of the Ashburton station, was quoted as saying that the results were definitely promising with D.D.T. for grass grub control but some points still to be cleared up. One of the points he made was that there was a possibility that some of the new insecticides might cause a taint in animal fats. A little less than five years later a bulletin issued by the Department of Scientific and Indstrial Research and quoted in “The Press” noted that D.D.T. had a wellestablished place in South Island farming as indicated by the rapid increase in the

acreage treated since 1950, when recommendations for its use had first been released. The use of D.D.T. in South Island farming, it was stated, was justified not only because it killed grubs and caterpillars, but also because without it superphosphate was- completely waited in areas of heavy grub and caterpillar infestations. Having been associated with the use of D.D.T. for pasture pest control since the start, Mr Kelsey, who is a great admirer of the old material, says that it is still the most reliable, safest and cheapest method of pasture pest control, and he even foresees the day when D.D.T. will come back again.