SOILS OF THE PROVINCE OF AUCKLAND. (No. 21.)

New Zealander, Volume XVII, Issue 1595, 31 July 1861, Page 3

SOILS OF THE PROVINCE OF AUCKLAND. (No. 21.)

DISEASES OF TIIH IVIIKAT FI,ANT. Not only arc tlie cereals, and wheat as the most valuable of them, liable during their growth to the ravages of insects, but tlie attack of parasitical fungi, which arc more or less destructive to both straw and grain, are equally to be dreaded by the farmer in this country Our lirst enquiry into the habits of the parasitic fungi, which are formed upon the wheat plant, will commence with one of its most common pests attacking the straw; and through the destruction of the straw during the growth of the plant, affecting the grain and causing it to become so shrivelled and deteriorated in quality, as to ho altogether unfit for the miller.

Along the entire length o' the straw dark lines or blotches, running parallel with one another, are plainly observable, and these in such a quantity as to give a crop, when badly affected, a rusty and blackened appearance in the field. This disease is the Puccinia. grtnninis, or as it is better known amongst farmers by its every day name of ‘•mildew.” When the disease first shows itself, the stem exhibits a number of dark colored spots or streaks underneath the outer skin, in a short time this outer skin or cuticle of the straw splits, and dark musty clust rs of spores appear in the opening. In order to make ourselves understood to the general reader we must, to show the cause and formation of this disease, enter slightly into the formation and functions of certain organs of plants. The stomata, or mouths, through which the processes of inhalation and exhalation take place, are found in the leaves ol all vegetables, and in the stems of the gramineous plants, including every kind of cereal tit present e.nlttva’cd in New Zealand. 1 here are small spaces which lie between the sides of the cells in the cellular tissue, and open into intercellular cavities in that part of the tissue lying beneath them. Ah hough not visible to the naked eye, by means of the microscope they may be very easily seen and examined. Now, during dry ivc'ither an I under the influence of lujht the stomata arc in active exhalation. It is clear then that the disease of mildew, coming as it does from sporulcs, or seeds contained in the moisture of the atmosphere, cannot enter flic stomata while the functions of those organs arc thus engaged. Bat on the other band, in wet and gloomy seasons, and where the crop is more than usually shaded from the light, and sheltered from the drying winds either by natural aspect or too many trees, nr even where free circulation of sun and air is impeded by too heavy and close a crop upon the ground, these functions are reversed, and in the place of exhaling, the stomata inhale powerfully. It is then, that in all probability, the sporulcs tire imbibed with j the moisture, and find it suitable place for vegetating when favorable atmospheric circumstances combine to assist them. The location of the spores of mildew in wheat straw, (as may be clearly seen by subjecting a portion of an affected stem to the action of the microscope). naturally induces us to conclude that the sporulcs enter by the stomata, not as in the case of another fungus, of which we shall presently treat, from the seed or soil, by means of the spongiolas of the roots. So exceedingly small is each individual spore of the mildew, that Sir Joseph Banks asserts that any single stoma on the stem would produce from twenty to forty, germinating in the hollow beneath it. It may bo easily perceived that these spores, though smal l , extending a* they do over so large a surface of the straw, sufficiently interrupt the sap from entering the grain, which it is designed to nourish, and thus cause

it to become defective mid shrivelled, ns in the case of mildew we accordingly lind it to be. Possessing then the theory of the disease, we are enabled to understand that which experience confirms—the causes, r r the circumstances which are favorable to its production and spread, and are able to guard against its attacks. Moist seasons, damp situations, over manured hinds, and more particularly lateness in the crop, are peculiarly favorable to the development of mildew, and fortunate it is, that although the atmosphere is always charged with ’these spomles, it is only under certain conditions of circumstances that they will grow. First, then, there is no doubt that over luxuriance in early growth is favorable to the mildew. Wo have ourselves grown wheat upon well drained land,— which had for nearly a hundred years been lying in meadow, until broken up and a crop of potatoes previously rnken off, —where the wheat crop was entirely destroyed by this disease, not more than eight bushels of grain being produced per acre, and that only of a quality lit for pigs. This was caused entirely by the too great richness of the soil. The same ground would have produced from 70 to 80 bushels of oats, as was the case in another portion of the field. The best method of checking such over-luxuriance, is to feed the crop down in spring with sheep for a few hours in the rlav-timo, or even to mow it with the scythe. Two hundred weight of salt on heavv. and four hundred weight, on light laud, sown broadcast, will serve to strengthen the straw and cause it to he less liable to become laid, when if a heavy crop there is sure to he more or less mildew. .Again, in places subject to mildew none hut early varieties should he sown, and a smaller quan-ity of seed used per acre. Another caution worthy of notice, is the avoidance of manuring immediately before sowing the seed, in nine cases out of ten, stray tnss eks of wheat growing on the edges of manure heaps arc effected by mildew. Attention shou'd also he, given to keeping the land intended for wheat free, from weeds. Mildew will seldom prevail to any extent where these precautions arc taken, and where the land has been thoroughly drained, —without which latter work, —farming never can or will pay anywhere, not even in this country of New Zealand. Mildew was once more prevalent than it now is in England ; and, doubtless, its diminution is in a great measure to he ascribed to the introduction of a better system of husbandry. Passing bv the diseases, ureila ruhign, and jireilo linearis, neither of which we have met with in this country, at least to any extent, we shall proceed at once to the examination of the uredo scgchan, or common sinni, or hunt ear, —a disease even more common in this country than the mildew. It reduces the car of wheat, oats, and barley, to a black smutty substance or dust. When we consider that it has been stated by scientific men that a single grain thus destroyed contains over four millions of spores, what must be the number of spornles, or germinating seeds, which these would send forth ? and as this disease is contagious, it will he readily understood how much care must ho taken to avoid its propagation, and the consequent loss attending it. We have frequently seen one-third of the entire crop sacrificed by smut in New Zealand, both in wheat and oats. Unlike the mildew, which as we have seen enters the straw by means of the stomata, the spornles of this fungus enter the plant with the tsconding sap through the spongiolcs of the roots. Considering, then, the immense number of seeds contained only in a single diseased grain, and that these arc liable to be blown over the standing crop in the field, or broken or hurst in threshing, and so mix with the sound wheat, and that these spornles are of an oily nature and so adhere to the healthy seed, —it is not to be wondered at that this disease, when proper precautions are not attended to, is so common and destructive as farmers well know to their cost. Even placing perfectly healthy grain in vessels or hags, which have previously held smutty wheat, will corminiy entail the attack of this disease. Various remedies are applied by farmers in the form of preparation for the seed, as a preventive. Chamber ley-salt brine, water in which blue-stone or copperas has been dissolved, and arsenic, are largely resorted to for this purpose. We have tried them all side by side, and must give our testimony in favor of a more simple plan than either, and certainly less objectionable than the use of some preventives, more especially that of arsenic. We hare never yet seen the crop effected by smut

whore the seed has been treated as we shall describe’ of course, after such a dressing care must be taken that the seed is not subjected to any fresh contagion, cither through using vessels or sacks in which smutty grain lias been kept, or sown in ground on which a smutty crop lias been recently grown, unless the land has been subjected to a full dressing of lime. Wash the seed in a tub of hot water, (not boiling, although wheat would not even lose its vegetating powers by simple immersion in boiling water), stirring it well about, and having then strained it through a basket or kit, spread the wet grain over the floor to the depth of two inches, sprinkle this layer over lightly with new dry lime, not too much slaked, add another layer of wheat and another sprinkling of lime, and so on ; then with a wooden shovel turn over the heap until every grain has received a slight coating of li ne. The moisture will be absorbed by the lime, and the wheat dry enough for sowing in a few hours. The action of the lime will entirely destroy the vegetating power in the spontlcs of the smut. Where this plan was tried side by side with the other remedies mentioned, seed from the same parcel being used in either case, that simply washed and dried with lime was entirely free from disease, while the others were all more or less affected by it. These, Puccinia or mildew, and the itrelo segetum or smut, are the only two diseases arising from fungi by which in this country our cereals seem to be affected. In the case of smut common precaution will ensure freedom from its ravages, and yet despite the serious loss which it occasions, too frequently from idleness or ignorance, we find the seed sown without any preparation whatever.

In the ease of mildew we arc less able, coming in the manner it does, to meet its attacks. Still, a clean system of husbandry, under-drainage, and a rotation of crops, which allots to wheat that place in the course, to which manure is not immediately applied, will eventually confine the attacks of mildew within very narrow limits.