FARM AND DAIRY

Waihi Daily Telegraph, Volume XXXVII, Issue 9204, 2 April 1938, Page 4

FARM AND DAIRY

RAGWORT CONTROL RUAKURA EXPERIMENTS SUPERINTENDENT'S REPORT

Important research work into the ways and means by which ragwort can be successfully controlled is now being carried out at the Ruakura Farm of Instruction and the following comprehensive survey of the work that is now occupying the attention of research workers at the farm was

given by Mr P. Smallfield, Fields Superintendent of the Department of Agriculture, to the first meeting of the Farm Advisory Committee at Ruakura last week.

Although sodium chlorate has been used for a number of years to control ragwort, it. has been found that under field conditions, and as commonly applied, it does not give a complete kill. The reappearance of a number of small plants following applications of chlorate are usually due to regrowth from roots which have been incompletely killed and not necessarily from seed from neighbouring farms. Although sodium chlorate has this limitation there docs not appear to be any other weedkiller that will as economically carry out the necessary defoliation of ragwort plants. The first experiment was to trace by chemical means the path of sodium chlorate through the plant tissues. Chemical tests for chlorate are based on its oxidising ..properties and these tests are also given by the oxidiing enzymes present in tlva plant. Hence chlorate could not be traced chemically, but fortunately this was counter-balanced by the fact that chlorate injury in ragwort roots gives a red colouration and could lie traced by observation. The next stage was to see how the plant was affected by chlorate. When rozette plants, 15 inches in diametor, were treated with 0.7 grain of chlorate in a 5 per cent, solution, the chemical was absorbed fairly gencr-

ally by the leaves and transported by the conducting tissue to the roots where it appears in the cortex, and not in the conducting tissue. The l chlorate travelled down the roots for a distance of six inches in the 14 days following treatment and within the next fortnight there was only a flight further spread. All portion'; of the plant above ground and the affected parts of the roots gradually rotted away till there was no sign of the plant. The remaining lengths of root were perfectly healthy, and in time many of them grew into new plants. Thus, six months after treatment, the original plant was replaced by, perhaps, a dozen young plants. LATER EXPERIMENTS

In later experiments, the amount of chlorate was increased from 0.7 to 20 grams (one gram is 1-2 S of the ounce) and some of the plants receiving these larger doses are recovering. The difficulty in obtaining complete root kills in the Ruakura ragwort nursery was, in part, attributed to the loose, cutilvated soil, which favoured an extensive root development, plants being obtained with a root spread of over seven feet. Consideration of these points led to the plants being sprayed in blocks instead of individually, and also to more emphasis being placed on lipid (rials.

In general, ragwort in pastures has not such an extensive root system and preliminary examination of some of (he plants in pasture already treated suggests that they will have better i root kills than those in the nursery The more compact soil, the mass of grass and clover roots, and the smothering effect of the pasture will make it more difficult for the remaining live roots to regenerate now plants. Considerable attention is being paid to this and a number of plants in Ruakura pastures have been 'treated with quantities of chlorate varying from 5 to 100 grams. In j rlaee of the plants there are now j dead patches which will later be top- j dressed to facilitate grass dominance and the choking out of any remaining live ragwort roots.