AN OLD FOE.

Waikato Times, Volume XXII, Issue 1827, 22 March 1884, Page 4

AN OLD FOE.

(rnglish magazine.) Wheat mildew is so common a pest in cornfields that we arc justified in regarding it as an old and much too familiar foe. The Royal Agricultural Society renentlj commissioned Mr W. C. Little to find out and bring down to date all that coald be ascertained respecting the attacks of the fungus, and this gentleman's report appears in the current number of the Society's Journal. There can beno*doubt that wheat milldew is one of the most costly of the un welcome and unbidden guests which the farmers has to entertain in his crops Mr Little estimates that in extreme cases the yield of wheat may Le reduced as much as 75 per cent by mildew, and the remaining quarter may be hardly saleable. In 1881, in Cambridgeshire, all the best wheat lands of a district promised a fine crop, but an attack of mildew came, and the consequence waa that the crop was one of the most wretched ever gathered. At harvest, many crops which ought to have yielded from 40 to 48 bushels per acre gave only 20 bushels, and some only 12 bushels, which a weight of not more than 431b a bushel. The monetary value of the lose in 1881 is put at £4 an acre. As we have on more than one occasion described the life-histoiy of Puccinia graminis, the fungus which produces the mildew, it is unnecessary, perhaps, to repeal it. Suffice it to say, therefore, that the organism propagates^ itself by means of minute spoies, that it presents several somewhat dissimilar stages in its cycle of growth, and that it possesses the property of;what the German botanist De Bary calls heteicecism (fiom heteros, different ; oikos, house), whereby it requires two host-plants to enablo it to go through the complete series of changes involved in its life history. Of these two hosts the wheat-plant is, of course, one, and there are strong reasons for supposing that the common barberry is the other. The disease under notice is often indifferently spoken of as mildew or rust. but in the report a distinction is drawn between an eruption occurring on the wheat plant in spiing and 'one which breaks out later on, the latter being the true mildew. The spi ing rust has been very common dining the early months of 1882 and 1 883 ;itis of a lighter colour than Puccinia giaminis, and is called Puccinia rubigo vcra. It is not often injurious to corn ciopsin England, and it has been noticed thut years in which spring rnbt is prevalent aie not always years of mildew. Whether or not the barberry is indispensable to the completion of the lifehistory of wheat-mildew is a question that still remains open. Some years ago we expressed in these column an opinion that such is the power of adaption to their environment which the micioscopic fungi possess, that in the absence of the barberry there might easily be found some plant capable of taking the place occupied by the barber) y as alternating host. And we went so fu as to opine that m heat-mildew might continue to flourish even though the baiberry should be utterly exterminated. We lefer to this again because we note, that Mr Little gives utteiance to an oppinion of the °arne kind, and is supported therein by observations of Mr C. B. Plowiight, of Kings Lynn. The report is largely based on replies to a series of questions sent out to vanous parts of the conutiy. Glancing over the, lisb of conespondents, we cannot help noticing the absence of the names of many persons who, we believe, were capable of furnishing useful information. We can place but little faith in generalisations respecting the immunity or liability of different Counties. The division of the land into Counties is of such a purely artificial chaiacter, and so utteily unconnected with geological, climatic, and other natural characteristics, that it seems as useless to speculate on the connection between a given atea of land called a Comity and the pi evidence or absence of wheat mildew, as to issue arbitral y restiictions applicable to given areas when foot-and-mouth disease is prevalent. An observation of n>ucli more value than that relating to Counties is this : that next to low-lying lands, those of great elevation and exposed situation suffer most, w hile the slightly elevated lands aie the happy medium. Spring frosts, heavy rainfall, and violent changes of tempeiatuie aie held to encourage mildew. In the Fen country it is commonly believed that crops injured by latefiosts are moie susceptible to attacks of mildew that are those which from some cause or other withstand the frost. This, however, points rather to some inlicient qualify of the seed, we should imagine, than to any direct connection between f tost and mildew. There is great unanimity of opinion on two points : (1) that ceitain descriptions of soil are most liable to mildew attacks than others, and (2) that a paiticular course of husbandry, or a particular applicatiod of manures, promotes the disease. Peat and clay soils suffer more than light lands, and wheat is moie liable to attack w lieu taken after clover than when following any other ciop. As to manuring, the genet al conclusion is that where a ciop has been stimulated and forced into lnxuimnt giowth it is more liable to fatal injury by mildew. The leports indicate that nitrate of soda is most frequently piodnctive of mildew, and farmyaid manuie ranks next. That there is a significant connection between the chemical constituents of the soil, and the liability to mildew attack of wheat crops growing on it is an oppinion supported by Sir J. B. Lawes, who considers that deficiency of mineral fcod in the soil is provocative of attack, while the gieater the amount of available mineral matter (potash, lime, silica, phosphate) at the disposal of the plant, the greater its power of resistance. Dr Voclcner has a very strong conviction that an excess of nitrogenous food in the solid as manure renders wheat liable to mildew. Again, he says that the richness of soils in nitrogenous matters renders them more or less liable ia cold, wet seasons to become attractive by mildew, and all the more so the higher they have been farmed, or the more farmyaid manuie there has been applied to the land. These opinions gave a scientific support to the farmers' conviction that whatever tends to pioduee over-liiMuiance of flag and stiaw renders the crop moie liable to mildew. An attempt has been made to ascertain which wheats are most and which leapt frequently meldewcd, but we consider the reports far too few in number to warrant any general conclusioi.s. Early in the century Arthur Young collected a series of opinions f i oin which he concluded that which wheat suffered much more than red. Mr Little's conclusions had better be given in his own words :—l.: — 1. It would appear that seasons are the chief cause of mildew, and that sudden changes oi temperatuie and lain, accompanied with close, still weather, are favourable fo the spread of the dissase. 2. That lowlying soils are most subject to attack. 3. That high farming and too generous manuring, particularly with nitrogenous manures, promote mildew. 4. That eaily sowing is desirable ou all lands subject to mildew. 5. That a thin and gathering crops runs more risk ef the disease than evently planted crop. 6. That while no ] description of wheat is proof against disease, red wheats are generally less \ injured by it than white wheats. If there is not much that is new in Mr > Little's report, it is due, not to any lack j of energy on that gentleman's part, but I to the very considerable difficulties by j which the subject is surrounded. Careful watching in the field, scrupulous notetaking ot what is observed, and a rigid cemparison of results from different localities— these are some of the means •whereby farmers may aid each other in baffling the attacks of one of the most ..pernicious pests of modern agriculture.

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