FACTS FOR FARMERS. THE POTATO ROT.

Waikato Times, Volume VI, Issue 311, 12 May 1874, Page 2

FACTS FOR FARMERS. THE POTATO ROT.

Titc generally accepted theory of the potato disease is that it is caused by a minute fungus — Peronospira infestaus — a fungus which affects tho potato leaf, stem, aud tuber. Let us assume that these, as are all other vegetables, are made up of cells, small closed cavities of microscopic size, roundieh or long, according to tho part of tho plant in which they may be. A cross-cut of either tho leaCatem, or tuber would appear under tho microscope iriuch like a honeycomb, it being liko that, made up in cells. This being in brief the structure of tho plant infested, let us consider tho fungus. The. potalo rot fungus is a minnte, microscopic plant, but a plant for all that as much as the potato itself is. It lives in the cells alrondy mentioned, and runs from one to the other, being nourished by their contents and substance. After a while, the mycelium having become sufficiently strong, it throws up reproductivo organs, corresponding to, though unlike in appearance to, mushrooms, and this is the visible mould or rot that is seen in tho item and leaf of the potato. The fungus has two ways of propagating. First, by the mycelium or spawn, which branches and spreads in the tissues of the potatoe, just as tho root of cot:gh-grass will spread through the soil. It lives on tho already prepared food in the plant, and needs no leaves, while the smallest portion of it will go on and grow and rnpidly multiply, and the fungus is ptopog^ted in- this way just as- we multiply a plant of a higher order by cutting of tho root or stem. The rust, blight, or rot, as it appears above the surface of the stem or leaf, is, when examined by the microscope, a collection of club-shaped threads, which ultimately produce an exceedingly minute dust or spores which in the fungus answer the purpose of scedi. Ihese spores are »o small that they can be carried about in tho air, or be transported unobserved while lodged on other bodies. From what baa been said, it will bo seen that in the potato-rot fungus we have to deal with an exceedingly subtle enemy. It cau, in tho first place, work great damage inside of the tissues of the plant before its ravages ore apparent, and it is propagated by spores or dust so minute as to escape detection. Tl/is being a brief history of the fungus, which science bas made out in- much greater detail, it will bo asked, What y«medy has scienco to , offer ? We are sorry to be obliged to reply, None. Some months Wince Lovd Cathcavt offered a prizo of £100 for the best essay on ' the potato disease and its prevention,' and in December lust, Messrs Charles Whitehead, John Algernon Clarke, William Carruthers, and H. M. Jenkins, the udges appointed by tha Royal Agricultural Society of England, to examine the competing essays presented their report at a meeting of the Society's Council. Among 94 essays, not one has been found worthy of au award ; in fact, had anybody really succeedad in combating tho disease, he would probably havo dono better with his discovery than by describing th« modus operand i for £100. The causes most , frequently set forth in the manuscripts were degeneration of the tuber, fungus on the tuber, superabundant moisture and wet weather. Peronotpera infestans attacking the leaves and stems of the plant, electrical action, and unhealthy condition of the plant, induced by the use of certain manures. The prinoipal remedies recommended were the cultivation of new varieties, use of disease-proof torts, employment of lightning conductors, application of hme as a manure avoidance of specified, manures, steeping or kiln-drying the' tnber beforo planting, dressing tho, haulm with sulphur, chlorine, &c, cutting off the tops on the first appearance of diaensp, growing the potatoes in small dumps or hillocks, bending down the haulm bo as not to to drip over the roots' and tying up the haulm to stakes, or cultivating sortt having erect stalks. Evidence in somo essays contradicted in nearly all enses alleged results stated in others. Tho judges have recommended the society to grant a handsome sum of money for tho purpose of inducing some competent mycologist to undertnke nn investigntion-of the hfo history of the "potato fungus (Pcronaspera inftstans) in tho interyal between the injury to the potato plant and the re-appearance of the fungus in tho following yoar. Also that valuable prizes should bo offered for the best disease-proof early and Inte potatoes, the nnard to be made after^ toting the competine sorts and their produco during thi'fe sentohs. The generally accepted theory described above, which we believe originated with Dr Julius Kulin, viz. : That the disease is caused by the fungus JPeronospera ittfestans has however, many opponent. Ton Schultzenstein is of opinion the cause of the blight u a withering or dying of the cellular tisiue and the vessels, and that it is only along with tho

chemical decomposition of tbe decayed parts at a later stn that the fungus makes its appearance. It is, too, a^sei^ that fungus growths rarely if ever ippear on healthy orM isms ; but this notion has been often refuted, and c scarcely be held as true. A curious fact has, however, be^ recently mentioned, which, shows that after all there may something in Yon Scholtzenstein's theory. A number | potatoes were left on the ground exposed to the sun, as wits thought they were all diseased- On examining thetrl few days afterwards about half were found to hare hi acted on by sunlight m tbe usual manner, being turned; dark #reen, while the remainder submitted lo exactly t same influence, retained their pale and sickly hue T would seem to show that some great change had been effect in tho constitution of the tubers ; and on examination tin which had greened were found sound, but the others wi all diseased. The editor of the English Mechanic and World of Scie offers the following suggestions : — " The different results c tamed in similar experiments in potato culture, the dive and conflicting opinions of those who hare studied the matt together with the utter inability to point out a remedy those who hare tho best right to our attention, have mvolv the whole subject in obscurity. Few pf us. can believe tl: if disease and its cause were really understood wo shoi fail so lamentably in grappling with it. There is good we in this direction for the Royal Agricultural or the Ro Horticultural Societies. Cannot they try experiments* raising new sorts, by crossing S. tubernum with anotl member of the Solanace®, and so, mayhap imp'avt some pi perty which will make the potato proof against the attad of the fungus.. There is hope that something may be accol plished by this means towards stamping out the disease j the new American sorts, which have hitherto been but ill aftecttd, giro an earnest that if m mudh skill, care, and d terprise are brought te hear on the potatoes have be] been lavished on florists* flowers, we may eventually obta a tuber as- greatly improred i» th» hardiness- and healthinj u tho flower* are in beauty." I