Residues And Pasture Pest Control

Press, Volume CII, Issue 30278, 2 November 1963, Page 6

Residues And Pasture Pest Control

Since about two months ago when “The Press’’ reported that the Agricultural Chemicals Board was recommending to the Government further restrictions on the use of D.D.T. involving the withdrawal of dry and wet-mix D.D.T. superphosphate mixes, farmers in the province have beerf giving increasing thought to the possible impact of these measures on the productivity and profitability of their farms.

At a meeting in Ashburton this week farmers from all parts of the province gained a little more information about the reasons for the pro. posed restrictions and the possible alternative materials that will be available to them tb protect their pastures.

While no-one at the meeting said plainly that use of wet and dry-mix forms of super would be prohibited from January 1 and that in the immediate future DDT prills would be the only practical form of control of grassgrub and porina, there was so much talk about these being the practical results of the measures envisaged, that it would be extremely surprising if the Government ultimately took any other action.

But in the light of the information available to the meeting that no alternative form of control yet available is as good or nearly as economical as DDT super, the meeting quite naturally sought a stay of the proposed regulations for a year so that there would be time to find the very best and most effective alternative procedures. and further, in the knowledge that the prills are slow in acting, the meeting also urged that in any transitional period from use of wet and dry mixes to prills, use of wet mix should be continued.

A significant aspect of the meeting was its acceptance of a resolution stating in part that it was recognised that something had to be done about the residue problem resulting from DDT.

Earlier the meeting had heard Mr C. Hilgendorf, a member of the Meat Board, who incidentally claimed to be one of the first and largest users of DDT and he hoped to be one of the last, say that when a few years ago the United States rejected meat from New Zealand on account of DDT and dieldrin residues, the Americans had been persuaded to give this country time to get rid of its residues The Government had then undertaken to do its best to eliminate residues from meat exports. Exporters at that same time had contended that they were likely to lose a great deal of money as a result of the rejection of meat shipments for residues and the board had agreed temporarily to indemnify them from loss, the exporters paying a levy of l-20th of Id a pound on export meat. But each year operators reported that they were still getting tests showing some D.D.T. This year the board had considered that the number of tests showing high D.D.T. content were too large and, in fact, there was even some indication that there had been an increase in the number of tests showing residues. Under the circumstances the board felt that it could not continue the scheme to indemnify exporters unless something quite definite was done about D.D.T. residues It was not the board's job to say how this should be done but it was necessary that D.D.T. residues should be eradicated from meat. Mr Hilgendorf said that 70.000 to 80.000 tons of beef worth about £ 20m were going to the United States. There seemed to be no likelihood of New Zealand’s beef being sent elsewhere. In the view of some exporters, if New Zealand beef did not go to the United States the price would drop to about £5 per 1001 b. It was the American market that made beef reasonably profitable and he did not think that this country could afford to lose that market

One of the main contentions of Mr R. Odinot. registrar of the Agricultural Chemicals Board, was that New Zealand had to work within the framework of internationally - established tolerances for chemical residues. For D.D.T. in the United States this was, for instance, 7 parts per million, but it could be revised down to only 2 parts. The board collectively could not accept responsibility for what was happening in New Zealand at present, he said. There were about 10m acres of pasture of which about Im acres had been treated on average during the last five years. Last year 1200 tons of DDT had been used in 75,000 tons of DDT super, of which half had been dropped out of aircraft and drifted over the country. “We cannot allow this to continue or recommend that DDT super be used in the manner in which it has been used in the past,” he said. He proposed that necessary changes should be made now. while time was available, at the same time maintaining production as far as was possible.

Mr J. M. Kelsey, officer in charge of the Lincoln substation of the entomology division of the Department of Scientific and Industrial Research, who has probably had more to do with the introduction of DDT for control of grassgrub and porina on New Zealand farmlands than anyone else, significantly recalled a test carried out by the director of the Dairy Research Institute which showed that correctly applied, under ideal conditions, DDT super need not constitute a hazard to primary produce. In this case where dry mix super was applied to long wet pasture and cattle were grazed on it immediately there was a residue of 182 parts per million in butter, but where it was applied to dry short pasture about three inches long and cattle were withheld from the pasture for three weeks, there was no residue in the butter. He added, however, that just under seven inches of rain had fallen during the three weeks.

Mr Kelsey indicated that from studies made of farmers’ methods of controlling grassgrub and porina 75 per cent of those who used DDT super used it only when damage from the pests showed up. Those who used these methods and continued to do so if only prills were available would be in for a dhock, he said. In trials at Halkett,* Mr Kelsey said, even after 14 inches of rain in four months no growth could be cut from plots treated with prills whereas there was six to eight inches of growth on plots treated with wet and dry mix super. However, over 15 months the prills had given good results, he said, though still not as good as wet and dry mix, but this might be due to a deterioration in pasture composition in the initial stages. He had no doubt that if prills were applied to good pasture in the absence of grassgrub or porina there would be good results. Of alternative materials available for control, Mr Kelsey said that diazinon, heptachlor and telodrin all gave quite a rapid kill and were initially better under trial than D.D.T., but they did not maintain this advantage and were not now as good as D.D.T. There was also the possibility of side effects with some of the possible alternatives. Telodrin, for instance, had a marked effect on earthworms. Diazinon, although it was one of the quickest to show up, had to be

• used at 21b of active I ingredient under Canterbury conditions and only lasted in the soil for four months and while this was advantageous from a residue point of view, now after one such treatment a pasture was significantly inferior to an untreated plot. There had been a similar result with another organophosphate material and before the use of these alternatives was recommended to farmers he would like to see the possibilities of side effects on pastures cleared up. Commenting about the effectiveness of prills. Mr Odinot agreed that there could be a time lag of two to three months and up to six months before they became active. - and if there was a possibil- • ity of farmers finding them--1 selves so placed that they t could not ensure protection of r their pastures as a .result of 1 the implementation of new 1 recommendations, he said that - there could be a case for 3 seeking an extension of time, r Mr Odinot said tliat dip- . terex, an organophosphorus 1 compound offered promise as a possible material for bridg--1 ing the gap between the withr drawal of D.D.T. super and ' replacement by prills. Mr . Kelsey agreed saying that it s had given quite good ret suits at Halkett without pas--1 ture deterioration. ‘ The present capacity of ? plants at Nelson and Hamil--1 ton provided for the produc- ’ tion of 6000 tons of prills a } year, said Mr Odinot, which • at 21b of active ingredient to the acre would enable the ? treatment of 840,000 acres but J production could be stepped - up to 10.000 toms or sufficient 1 fdr treatment of 1,250,000 ■ acres. At the same time, Mr Odt inot said, one granulation » plant in Hawke's Bay could ’ produce 40,000 tons of granulated DDT super ani nually. A possibility that . was being looked at as a f means of bridging the gap t caused by the possible with--1 draiwal of wet and dry mix i super was the raising of the . concentration of part of 1 the granulated super proi duced by this plant by two, i three or four times so that . it could be sent to the South r Island for further mixing in . South Island works for use 1 by South Island farmers, r Mr Kelsey said that a comr pany in Nelson was also 1 making a DDT super concen--5 trate. : When it was proposed that • special consideration should I be given to Canterbury in s restricting the use of DDT ‘ superphosphate, Mr Odinot ! said that almost every dist trict could come forward s with an insect problem of ■ equal importance. Asked whether he had any ’ evidence that Canterbury ■ was a bad offender in having 1 residues in its export pro- ' duce, Mr Odinot said he had : been assured by the direch tor of the meat division of 1 the Department of AgriculJ ture that Canterbury was no > better or worse than any ; other district. ] Mr Hilgendorf said thait . while it did appear that the I Americans were a little more I fussy about New Zealand , meat than their own. there ’ was in the Meat Board’s opinion no evidence that they r were using DDT residue levj els to exclude meat from . their country. i The meeting decided to s urge Federated Farmers to > press for manufacture of i granulated super. Mr Kel--1 sey said that this would be worth while to ensure that i the super they applied would , in fact land on their own s properties.