WEEDS IN STREAMS

Press, Volume CII, Issue 30115, 26 April 1963, Page 19

WEEDS IN STREAMS

Experiment Of

Chemical

The Department of Agriculture will be asked by the Christchurch Drainage Board to experiment with weedkillers in one or more of the streams controlled by the board.

Mr H. F. Page, the chief engineer (operations), reported to the board that more experimental work was required to flowing streams before there could be any certainty on the effeettvenesand treatment costs with the weed-toller, a chemical called diquat. The works committee warned that the weed-killer was a contact kilter, so aerial application might cause destruction of grassed areas near the river. The North Canterbury Catchment Board had had good kills in drains with flows of three to five cusecs, the committee’ said. A trial on the Halswell river, where the flow was 32 cusecs, was not successful, but this might have been because the type of weed was resistant to the concentration used.

The board was als< advised by a private company that the nuisance in the tidal reaches of the Heathcote and Avon rivers resulted from loose floating weed and household refuse which was carried back upstream by the incoming tide and which never got clear away into the Estuary. The company suggested that three comparatively simple booms at strategic points to allow the debris to pass but to prevent its retetm would solve the problem. Mr Page said there was some merit in the idea, and the board granted £2OO towards the cost of setting up an experimental working boom and a detailed study.