Australian Grub Spreads

Press, Volume CVIII, Issue 31772, 31 August 1968, Page 10

Australian Grub Spreads

While confirming this week that over-all grass grub and porina damage had been much less in the province this winter, Mr J. M. Kelsey, officer in charge of the Lincoln sub-station of the Entomology Division of the Department of Scientific and Industrial Research, said the Australian grass grub was definitely spreading.

The important feature of this pest was that it had the ability to destroy quite well established stands of lucerne —it could completely destroy the crowns of lucerne plants. It also cleaned up weeds and storksbill was one of its favourites. In the last six years, Mr Kelsey said, it had spread

from Banks Peninsula and the Waiau districts to Tinwald in Mid-Canterbury and as far as the foothills. It liked the Lismore silt loam but not the heavier soils.

Counts had shown as many as 60 to 68 grubs to the square foot and they had been reducing pasture growth by well over 50 per cent Mr Kelsey said that like porina the Australian grass grub was a leaf feeder so it could be expected that materials applied to the plant leaf would kill it but this has not been the case. Not one of some 22 materials used in two trials last year had worked, and this year more materials had been added so that some 36 were now being tested in four trials, including the two laid down last year. The effect of these materials would be assessed In the next few weeks. It had, however, been shown in farmer application, said Mr Kelsey, that D.D.T. could be effective against the grub in the second year after

its application. This had been demonstrated on the Ellesmere spit Mr Kelsey said the over-all picture of ordinary grass grub in Canterbury this year was that it was of less consequence than for the last two years, although there were still odd areas, such as in the West Melton district, where it continued to be a serious problem. Here the growth in some pastures had been reduced by 50 per cent and in some cases much more. The decline in porina this season seemed to be even more marked than in the case of grass grub, he said.