Granulated D.D.T. For Grass Grub Control

Press, Volume CVI, Issue 31345, 15 April 1967, Page 10

Granulated D.D.T. For Grass Grub Control

The main hope for the control of grass grub and porina lay in the use of granulated D.D.T. super, Mr J. M. Kelsey told the Under-Secretary for Agriculture (Mr D. J. Carter) and Federated Farmers’ representatives at Ashburton this week.

Mr Kelsey, who is officer In charge of the Entomology Division’s Lincoln substation, said trials had shown it was giving a more effective response than D.D.T. prills. But he said that there were no fertiliser works in the South Island able to meet the general demand for granulated D.D.T. super, although the three farmers’ fertiliser works in the North Island had gone over entirely to granulated super output. Earlier in the day, Mr Carter, Mr Kelsey, Department of Agriculture officers and Federated Farmers’ representatives had visited five properties in the Carew, Ealing and Hinds districts, where pastures had serious infestations of grass grub and porina. One property is faced with reducing its ewe flock by 300. During the inspection Mr Kelsey identified D.D.T. prills which had failed to dissolve although applied a year ago. At a meeting in Ashburton later, Mr Kelsey said the porina and grass grub damage was worse than had been thought. So far as porina was concerned, the situation was fairly clear-cut, three materials for control being readily available. Grass grub was by far the hardest proposition. “The answer to the question of whether we have a solution is yes, but at a cost,” he said. At 21b an acre, D.D.T. prills had failed at Carew last year, but in February last his division put down 21b of granulated DJ).T. super in a trial at Halkett, and there was now a response. “I think our objective should be to get this granulated D.D.T. super,” Mr Kelsey said. "The residue, we are told, is no greater than with D.D.T. prills.” Asked by Mr Carter if there eould be a reversal of the situation next year, if condi- ' tions were not favourable to grass grubs, Mr Kelsey said : that in trials covering 22 1 years there were only two 1 occasions when there was a 1 sudden cessation of the grass grub population. ] On present knowledge of i trial plots, the grass grub 1

i population next year was ■ more likely to be up than , down. [ To Mr C. P. Whatman, • senior advisory officer of the Department of Agriculture at , Ashburton, Mr Kelsey said he ' could not give a dear-cut : answer as to whether granulated super would have to be ’ put on in the spring to get re- ; suits. At Halkett there was a response in four weeks although the rainfall, at 4in, was a little more than usual. But granulated D.D.T. super, ’ applied in February, should give protection the same season. Mr Kelsey said that although he and other officers had been working for 22 years on the grass grub problem, they stll did not know a lot about the build-up of grass grub. At present answers were being sought about the economy of the grass grub problem—how it affected the farmer—what was the buildup in the grass grub population in a given paddock year by year, what was the percentage of a paddock infested each year, and what was the position in the average light Canterbury soils. Mr Kelsey said it was very hard to make an accurate forecast of the grassgrub situation. Last year’s infestations were a contradiction of forecasts made a year earlier.

The D.D.T.-resistant areas would probably not be more than 5000 acres in Marlborough, Canterbury and North Otago, but there were also anomalies here. On one place at Carew one paddock had been a proved D.D.T. failure, but an adjacent paddock did not fail until this year. The first property visited was that of Mr R. A. N. Penney, of Carew. It was here that Mr Kelsey Identified undissolved prills. Mr Penney said there was not a paddock on his property which was not infested to some extent He had tried every available method of control. Severe damage had not occurred until dry-mix D.D.T. had been banned.

Mr Penney showed the party a five-year-old pasture and a three-year-old pasture, both of which had been top-

dressed with the prill form of D.D.T. last year. Answering questions from Mr Penney, Mr Kelsey said that if birds followed the cultivation it was possible to reduce grass grubs from 60 a square foot to one a square foot, but unfortunately this also got rid of the earth worms. To achieve this reduction of grass grubs would require five grubbings. If five to seven grass grubs a square foot were carried over into a wheat crop there could be considerable damage. Mr Kelsey thought the main problem with Mr Penney’s three-year-old pasture was the failure of the D.D.T. pellets to break down. Mr Penney said that in the 12 years he had been on his property this would be the first year he had not increased his stock numbers. This year he would have 170 of his 660 acres in crop, but this was really sheep country and he could not go on cropping. Another Carew fanner, Mr R. J. Bush, said be took up 540 acres on his own account in 1960. From 1200 ewes and 400 hoggets, plus a little crop, be had built up to 1500 ewes and 500 hoggets, but he could not go much further. The whole of his property received D.D.T. every two years. Up until two years ago, he was putting on lewt of super an acre, but had increased it to 2cwt with extrastrength D.D.T.

One of the most spectacular infestations was seen on the property of Mr L. M. Watson, at Ealing. A pasture put down in the autumn of 1964 looked as though it had been lifted with turf harrows. Mr D. K. Mackenzie, who deputised for Mr Watson, said super with D.D.T. prills had been applied in 1965, and again last autumn. This year 440 acres had been sprayed for porina, and 200 acres treated with lindane pellets.

Mr D. G. Reith, who farms 600 acres at Ealing, said he had patches of grass grub right through his farm- It was twice as bad as last year. “That is the general pattern,” commented Mr Whatman. “It showed up last year, and the big build-up is evident this year. What could it be like next year?” The party again saw very severe damage to pasture on the property of Mr G. Sugrue, at Hinds. When Mr Sugrue and his brother took over the place three years ago they embarked on an extensive development programme, raising the ewe flock from 1600 to 2700.

Speaking on their behalf, Mr B. P. Royds said that be-

cause of the severe grus grub damage it was planned to put in 100 acres of wheat, but it wu recognised that they should not grow wheat on such light country. Four hundred acron of the 1140-acre property had been cultivated by one man alone last year. This year there would be a further 60 and some contract labour would be required. Mr Royds said there would be no profit in wheat at 35 bushels an acre so on the 60acre paddock inspected by the visitors the owners would be involved in an expenditure at £6OO getting it back to grass again. Because of the serious effects of gnu grub, the property wu faced with selling off 300 ewes. Discussing granulated D.D.T. super later in Ashburton, Mr Kelsey said the present product from the North Island works wu much better than the earlier product which contained a proportion of fine D.D.T. which gave a high residue.

Mr Carter said it weald be reasonable fer the Government to assist farmers to get granulated D.D.T. super. This wu not an offer on his part, but a hope, and he would discuss the matter further in Wellington. These infestations meant a less to the farmers. They also meant a loss to the Government which wu concerned to beep up export income.