What sort of chemical for barley grass?

Press, Volume CXII, Issue 33004, 25 August 1972, Page 8

What sort of chemical for barley grass?

For several years all the work of the Department of Agricuture and the chemical firms had been done with selective control of barley grass in mind, Mr A. G. Wasmuth, of May and Baker (New Zealand) Ltd, told the conference of the New Zealand Weed and Pest Control Society in Christchurch last week, and if his paper raised doubts about this concept then he would feel he had done his job.

Mr Wasmuth reported to the conference on a survey that he had organised aimed at determining the attitude of the average New Zealand farmer to the barley grass problem and he used this information to back up his doubts about selective control of the weed grass.

Some 166 farmers were Involved in the survey and of these 53 were in Canterbury. Slightly more than half of the farms were devoted solely to sheep and a similar percentage were greater than 500 acres in areas.

It was found that generally the area infested by

barley grass was quite small — 34 per cent of the farms had about an acre infested and 36 per cent between two and five acres, and only 21 per cent more than 10 acres affected.

At the same time half of the farms had the weed only in clumps — in fence lines and in stock camps etc. — while half had a general over-all infestation involving stock camp areas as well as a general invasion of most pastures. When the farmers were

asked what their criterion was for a satisfactory barley grass herbicide, 15 per cent felt that weed selectivity in pastures alone was of major importance, 43 per cent wanted 100 per cent control even at the expense of selectivity, and 43 per cent required both selectivity and control. "The answers to these 3uestions obviously reflect le unsatisfactory state of control obtained by herbicides that have been used up to the time of the survey and indicate the standards expected for any future barley grass weedkiller,” Mr Wasmuth said. Mr Wasmuth then suggested that in the predominant clump situation — they existed on 100 per cent of farms — where there was 90 per cent of barley grass, selective control was not so important and work should, in fact, be directed to doing what would result in the most benefit.

However, not all of his listeners agreed with this proposition and it was

noted that if everything was taken out by a chemical something had to be put back and Dr M. J. Hartley, the secretary of the conference, who as a scientist at Ruakura agricultural research centre, contributed papers on the subject, said that she would not like ,to see much ryegrass removed.

Mr Wasmuth and other speakers, however, agreed that an over-all management approach to the problem was needed, with the use of chemicals being one of the tools in this. Mr M. L. Smetham, of Lincoln College, for instance, noted that Mr Wasmuth had said that the cause of stock camps, a favourite area for infestations, had to be removed, and so he said that the practice of feeding hay in one paddock all the winter must be eliminated. However, it was also noted that elimination of the weed from such areas could in theory, at least, prevent the spread of the weed grass to other areas. Reporting on trials in the Waikato in which lambs were grazed on barley grass infested pastures and areas that had been sprayed, Dr Hartley said that the increased production obtained on the sprayed areas had more than offset the cost of chemical treatment, and she felt that people with a heavy infestation could really not afford not to spray.

The growth rate of the lambs on the sprayed areas was greater in spite of reduction in dry matter production, and Mr G. C. Atkinson, who was associated in the studies, and Dr Hartley, said that this probably reflected the effect of a change in pasture composition towards clover dominance and possibly the low palatability of barley grass.

The growth rate of the lambs on the barley grass

infested control areas was severely checked from January through to March, being associated with a high level of eye damage. The damage to livestock was possibly even more severe than farmers realised, said Dr Hartley, who showed slides of lambs whose eyes had been penetrated by barley grass seed. “During late January and throughout February many of the control lambs were completely blind and were a pitiful sight,” the two workers said in their paper. In another paper, based on another Waikato trial, the two discussed the damage caused to lambs by barley grass. The relationship between weight gains or losses and the amount of barley grass in the pasture indicated that barley grass had depressed lamb growth rate. Post mortem examinations on four lambs selected at random showed high levels of internal parasitism. Thus the ill thrift was probably aggravated by parasitic worms in spite of dosing before the trial and at each subsequent weighing. If the effect of the barley grass was expressed indirectly by way of worm infestation, this suggested either that barley grass being unpalatable and laxly grazed allowed greater worm survival, or that a predominantly barley grass diet reduced the lamb’s vigour ' and its resistance to the parasites. The physical damage with the finest grass, especially to the eyes, also seriously depressed lamb growth rate. The number of seeds found in the fleeces was surprisingly low considering the amount of barley grass present, and Mr Atkinson said in response to a question that a moderate infestation of barley grass gave as much damage in pelts as a heavier infestation. There was an observed relationship between wool characteristics and seed content, they said. The finer wools picked up more seed than the coarse wools. The Down type carried more than the Border Leicester type, with the Romney being intermediate. A positive correlation was shown between wool characteristics and pelt damage. However, the data indicated a lessening of pelt damage with the finest wools (525, 565) and if this result was confirmed it might imply that, although the fine wool would pick up more seed, these seeds did not reach the skin.