Drift Major Factor In D.D.T. Problem

Press, Volume CII, Issue 30269, 23 October 1963, Page 15

Drift Major Factor In D.D.T. Problem

(From Our Own Reporter) WELLINGTON, October 22. “Even if all fanners stuck to the regulations governing the use of D.D.T. on pastures, they could be causing damage unwittingly through drift beyond their control,” said Mr L. J. Matthews, technical adviser to the Agricultural Chemicals Board, today.

He was replying to criticism from Dr. R. A. Harrison, senior lecturer in agricultural zoology at Lincoln College, who, speaking at the Ashley Dene held day last week questioned the competence of the Agricultural Chemicals Board to bring down constructive regulations on the use of agricultural chemicals.

"While we have drift tn the application of chemicals." said Mr Matthews, “we cannot make a prosecution, because investigation of numbers of cases of suspected wrong use of DDT. has shown that the farmer whose produce was affected had not used the particular material "The farmer's claim that he had not used the material could weU be substantiated, as 42 per cent of an application of dry mix DDT will drift, and in a two-knot wind from a spinner topdresser DDT drifted up to detectable distances of 200 ft from the target ” Few people realised, said Mr Matthews, that one teasnoonful of D D T. to an acre of dairy pas'ure was suffic ent to cause contamination of produce.

Referring to Dr. Harrison's s atement that "perhaps the chemists are not able to pick up the residues correctly." Mr Matthews said that present techniques could detect a$ little as one-thousandth of a microgram of contamination, so that t!< analytical procedure was unlikely to fail to pick up residues. “We could never reach the stage where day-by-day analysis could be done of a farmer's produce.” said Mr Matthews. It was therefore essential to remove the factor of drift

If chlorinated hydrocarbons were restricted to a pelleted form, drift would be cut out or minimised, and offending persons supplying contaminated produce to factories and meat works could be prosecuted. Expert Advice Dr. Harrison asked whether the Agricultural Chemicals Board had taken the advice of entomologists Mr Matthews said that fellow-mem-bers with him on the pasture insecticides committee, which advised the board, w ere Dr W. Cottier, director of the Entomology Division. Department of Scientific and Industrial Research. Nelson: Mr J Kelsey. Entomology Division, Department of Scientific and Industrial Research. Lincoln: and Mr G A. H Helson. chief advisory officer < entomology). Department of Agriculture. Wellington.

This committee, after examining trial evidence on drift of DD T. superphospha:e. brought down a recommendation. adopted by the board, that if residues of chlorinated hydrocarbons in animal fats were serious enough, the application of these insecticides to pasture should be limited to pelleted formulations

Alternatives Referring to Dr. Harrison's statement ‘-bat after January 1 it was likely that only the use of DDT. prills would be permitted. Mr Matthews said that committees of the board representing agricultural chemicals manufacturers. aerial applicators fertiliser manufacturers, and other interested bodies were called to dscuss the proposals. Alternatives to prills were granulated D DT-super-phosphate and a concentrated granulaited D.D.T. which could be incorporated in ordinary superphosphate. It was known tha< pellets did not act as quickly as dry

and wet mix D.D.T.-super-phosphate in dry conditions, but under normal rainfall the difference was not so apparent.

Dr. Harrisoti could be assured that other materials were being looked at, including an organic phosphate compound, diazinon. Its effectiveness was apparent from its extensive use as a sheep dip, and Lt was so safe that against pasture pests it might be applied in granular form even while paddocks were being grazed. Present indications were that this material would be available at prices competitive with those of other pelleted materials

The Agricultural Chemicals Board called on the bes: advice available in the country before considering legislation. said Mr Matthews. It was realised that after two years in operation the existing regulations were not protecting New Zealand’s export primary produce because it was now known to what extent drift occurred with wet and dry mix D.D.T.