POTATO CULTIVATION.

Manawatu Herald, Volume XL, Issue 1859, 1 August 1918, Page 1

POTATO CULTIVATION.

PREVENTION OF BLIGHT. RAVAGES LESSENED BY DEEP PLANTING. Writing to the Christchurch Press Mr William Martin, Director of Agricultural Instruction, Christchurch, says: — “I would like to reply to a number of articles occurring in both the Press and Weekly Press, in which I am credited with discovering the fact that deep planting is a preventitive against the ravages of potato blight. First, I would like to say that I claimed no such discovery, for I am well aware that this is a fact of long standing. What really took place is this; In a recent report to the Education Board I drew attention to the fact that many children and teachers had discovered hat few, if any, tubers at a depth of six inches or more showed signs of being affected with blight. This to them was a real discovery, and I mentioned it as evidencing that useful information was being gained at first hand by the children of the schools. “Now that the subject has been ventilated, it is, perhaps, advisable to add a brief note. Deep planting does reduce the ravages of blight in the tubers themselves, but for obvious reasons deeper planting under field conditions is not advisable, even if possible. However, if the rows are spaced well apart (28in. to 30in.) it should be possible to mould up deeper than is practised by many farmers in this district, and the same end can be achieved. But dee]) planting is neither a remedy nor a preventitive against the tops being damaged or rained by blight. The only wise procedure is to spray, the leaves with Bordeaux Mixture (4-1-40 strength) about Christmas, and if the weather be damp, again at intervals of a fortnight and three weeks, 1!' every leaf could in practice be coaled with spray the crop would be quite immune from blight, but as this is hardly possible, it is only possible* to claim Unit the blight will affect the crop in inverse proportion to the care taken in spraying. Small users can buy small tins of Bordeaux Basle ready to dissolve in water. At a symposium of Canterbury potato growers, held tit Willowbridge in 1013. which it was my privilege to address, it was the unanimous opinion of forty growers that 1 Ik* worst results to be feared if the crops tire sprayed and well moulded up. is at most a loss of 30 per cent., whilst most agreed that in the absence of blight, spraying resulted in an increase of two to live tons in the crop, due to a thickening of the outer skin of the leaf, with a consequent lengthening of the growing period. Personally. J do not flunk that the tubers are ever affected by spores tailing on the ground, unless in the ease of damaged potatoes, or potatoes completely exposed to the air. Twice I have attempted to affect tubers by dusting spores on soil just covering the tubers and lying loose, and also directly on the tubers, and no infection resulted in either case.. I imagine that tubers are usually affected as a result of the myceium of the fungus, following the course of (he digested sap as it travels from the leaves, but this view is still disputed. I propose to arrange for more extensive tests during the coming season. 1 suppose I need not remind your readers that the “blight” consists of multitudes of tiny parasitic plants (fungi) that live on the potato plant, and secure, their nourishment at its expense, and that rapid spread of the blight in damp weather is due to the enormous rate at which these plants produce spores which germinate on the moist leaves of other plants. When a crop is badly affected, it is customary, and, probably, a wise procedure to cut the tops off, and thereby prevent the blight travelling down the stems into the tubers.