Potato Stem Rot.

Taranaki Daily News, Volume XLVII, Issue 7727, 1 February 1905, Page 3

Potato Stem Rot.

The following clipping, taken from The Field of 22nd October last, appears to throw new light upon one of the diseases which; are at present devastating the potato crops in portions of the Auckland province : *■' As if the tubpr crop had not enough enemies of the lower order already to contend with, another has just been added to the list. This is black leg .or potato stem rot, regarding which a leaflet has been issued for gratuitous circulation |by the Board of Agriculture. The disease, though little known in this country, apparently has been causing mischief for some time on the Continent, and especially in Germany, where the loss attributable to it has sometimes amounted to 75 per cent of the entire crop. As the malady is comparatively strange to British growers—and it is sincerely to be hoped that it may long remain so—it muv Ije useful to give some of the symptoms. The leaves wilt and turn yellow ; then they become shrivelled from below upwards, and finally die. If the underground portion of the stem is 'examined when the leaves commence to droop, its surface will be found to lie more or less covered with brownish stains. This discoloration gradually extends up the stem, which finally becomes black and rotten throughout. The number of plants affected in a potato iield varies very widely, and diseased plants may be found glowing amongst perfectly healthy ones, although more frequently' the disease spreads from one plant to another. It has -been discovered that the disease is caused by a bacterium called bbcillus phytophthorus, bat as decay proceeds various kinds of fungi, Mich as moulds, etc v assist in the completion of the work. The malady, like most others of the kind, spreads with the greatest rapidity .lining hot damp weather, and is most al>undant during the months of .Tune and July. It is remarked that the death of the haulms so early in the season, particularly in the case of * late varieties, means serious loss, not only on account of the scanty crop, but because the tubers also become infected by the bacteria that have been washed into the soil from the rotten haulms. Dr Otto Appel, who has devoted much study to the disease in Germany, has suggested the following measures for dealing with llic disease : (1) Potatoes, as well as beans, carrot, turnips, cucumbers, vegetable marrows, sugar beet, and mangels, which are also susceptible to the disease, should not be cultivated for two years on land where the disease has occurred.- (2) Potato sets should not be cut, but the tubers should be planted whole. (.'!) Care should be taken to obtain seed from districts where the disease does not exist. (4) Lime or strong nitrogenous manures, especially nitrate of soda and sulphate/of ammonia, should not be used. 'lt has been proved by experiments that the disj: case does not attack cereals, but aph, _' parcntly nearly all the other coms.- mon crops of the) farm and market fi; garden come alike to the scourge. g||£; Jhe disease would seem to differ in ■§ljL""°me vital respects from the better W^feft?? 3 ? '.J* ctcr i a l ailments, in that ||HfjHfflffljfl]|B{HtSf. -rather than checks