HOW TO OVERCOME THE POTATO DISEASE.

Daily Telegraph (Napier), Issue 3549, 23 November 1882, Page 4

HOW TO OVERCOME THE POTATO DISEASE.

Mr J. L. Jensen, director of Bureau Ceres in Copenhagen, lias published a valuable pamphlet on " How to Overcome the Potato Disease by a simple, easy Method of Cultivation." The pamphlet is mainly directed to British fanners. Mr Jensen states that in this country 1,400,000 acres are devoted to potato growing, and quotes the opinion of Professor T. Baldwin that the loss on the 850,000 acres of potatoes in Ireland in 1879 ■was nearer £8,000,000 than £6,000,000. The damage to the whole European crop, he states, must be reckoned by scores of millions of pounds, and continues:—'But these extraordinary great losses may henceforth be diminished in a very considerable degree, and even the most violent attacks under the most favourable circumstances for the development of the disease may, as a rule, be almost neutralised.' And to teach this is the purpose of his paper. Mr Jensen says it is useless to fight the enemy—the fungus peranospera infestans—m the open field, • but,' he says, ' the fight may be fought successfully after the manner of a siege.' Two sets of experiments were made in the experiment fields of the Agricultural Institute to Copenhagen, to test how the tubers were affected according to the depth of their covering with jsoil. First experiment —Uppermost tubers, of which 49 per cent, sick, depth iin to 3in ; middle tubers, 7121b., of which 22 per cent, sick, depth 2in to 3in; lowermost tubers, 5-951b, of which 8 per cent sick, depth 3in to 6in. Second experiment — Uppermost, 5.501b., of which 82 per cent sick, depth -Sin to 2in ; middle, 51b, of which 30 per cent, sick, depth 2in to 3in ; lowermost, 361b, o£ which 3 per cent, sick, depth 3in to 6in These appear to have led to the adoption of Mr Jensen's remedy. He recommends that the potatoes be planted in a low drill, 30 inches apart, and three or four inches high, ■with a flat top of ten or twelve inches wide. According to answers from 150 growers, potatoes planted in drills of this kind gave a yield of nine per cent, more than potatoes planted in the ordinary drill. But Mr Jensen's plan is, about the time the disease appeal's —which should be carefully watched for —to throw up another moulding upon the base of the flat-topped drill. He places the tops of the potatoes at an angle of 45 degrees •with the water level, so that the spores of the fungus do not run down tho stem to the tuber, but fall into the space between the drills, and become comparatively harmless. The extra earthing, which he calls ' protective moulding,' is performed by a plough, which is furnished with mouldboard, supplied with triangular plates or ■wing?, which are adjustable to the width of the drills. In front of tho share a pair of goosefoot-shaped irons are placed for scuffling and pulverising the soil, as it is important that the soil be fine, and that the top? of the drills be freed of weeds before the protective moulding is done. Experiments were tried in 19 different localities in Denmark, Jutland, the ilslands of Funen and Zealand; and the average disease in 11 irregular experiments was by moulding in the usual -way fiat 16.6 per cent.; less flat, 14.0 per cent.; by protective moulding, imperfect, 11.4 per cent. ; and by perfect moulding 10.4 per cent. In the eight regular experiments which were made under prescisely similar conditions, except the moulding, ' the disease,' Mr Jensen tells us, ' has on an average been diminished from 23"4 or 18'7per cent, to V 4 percent.' These experiments were taken during a period when the rainfall at the experimental stations was about 66 per cent, greater than customary in Denmark, and about 42 per cent, greater that the average rainfall in western England and Ireland. Not the least interesting feature of Mr Jensen'a paper is the part devoted to tiny creatures of the earth.. It ■was thought that insects, grubs, worms and similar aimated little things which have their dwellings and walks in the ridges or hills of earth about potatoe plants, conducted to the spread of the disease, and Mr H. Dreyer investigated this matter, under Mr Jensen's directions, with the following results :— ' The average disease of the potatoes was, for all cases without worms, &c, 22 per cent.; with the worm, 35 per cent.; with two worms, 46 per cent ; with three worms, 58 per cent; and with four ■worms, 71 per cent. ;' increasing at the rate of 12 per cent, for each worm added. Mr Jensen carries his advice to the protection of the tuber against after disease, and states that ' the lifting ought not to take place before at least two or three weeks after all the leaves are perfectly withered. The more this is neglected, the greater is the risk run of having the produce spoiled if there be any disease at all in the top, and this will, as a rule, be the case.'