THE BLIGHTS TO WHICH OUR CROPS ARE SUBJECT.

Southland Times, Issue 1610, 26 July 1872, Page 3

THE BLIGHTS TO WHICH OUR CROPS ARE SUBJECT.

Blights are occasioned by the growth of minute fungi. Ever since plants have existed, these vegetable parasites have preyed upon them, less or more, every year. They are fostered into excessive growth by certain favorable conditions of soil and climate, and checked in their development by unfavorable conditions. There are four diseases in corn produced by fungi — Smut, Rust, Bunt, and Mildew. Sometimes one, and sometimes another predominates, but there are few farms where they may not all be found in some slight degree. Any one who has examined a field when the corn is coming into ear, must have noticed black heads : among the g^een ones, covered with a soot-like dust, which comes away freely, and stains the hands. This is Smut, or \ Dust-brand, but it is only recently that i its true nature has been ascertained. Under the microscope, the black powder is found to consist of a collection of spores, or round seed cases, containing sporules, or seeds, in tbeir interior. It ! is, therefore, not a mass of diseased cells, [ as was formerly supposed, which obviously I would not germinate, but a parasitic plant i — a true fungus, capable of reproducing and extending itself indefinitely. Hence, \ botanists have given it the name of Usfci- • lago Segetum. The seed vessels in this s plant are exceedingly minute. One square ' inch of surface contains no less than eight ' millions ; and if the seed vessels be so [ small, what must the seeds be! The , highest power of the microscope is only > capable of resolving them into an impalr pable powder. Myriads of seeds are shed ' from the smutted ears long before the ' corn is ripe, and dispersed into the air T and over the fields, — most of them to die, b a few of them to reappear next summer • with the on grain which they are paraI sitic. When germinating, this fungus \ first attacks the interior portions of the . flowers, and renders them abortive. It f then seizes upon the little stalks of \ the 3 florets, and causes them to swell and beb come fleshy. At length it consumes all f the reproductive organs, and converts the ? whole nutritious grain into dust. Another I I species of blight (more destructive and

! therefore mora to be dreaded), is commonly known by the name of Bunt, to botanists as TJstilago "Fcetida, on account of its intolerable smell. It confines its ravages entirely to the grain. Externally, the infected ear presents no unhealthy appearance. There is no black dust, no stinted growth or malformation by which its presence may be known. On the con--1 trary, the infected ears continue growing, and appear even plumper aud of a richer grain than the sound ones. It is not — in many cases — till the wheat is ground into flour, the discovery is made by the smell and color, that it is unfit for human food. Under this outward appearance of health all fecundation is rendered impossible, there is no development of the parts of fructification; no embryo whatever can be detected ; the whole interior of the seed when broken or bruised is found to be filled witb a black fetid powder, which I contains, on chemical analysis, an acind oil, putrid gluten, charcoal, phosphoric acid, phosphate of ammonia and magnesia, but no trace of starch, the essential ingredient in human food. Under a high power of the microscope, this powder consists of a mass of round spores, or seed vessels, considerably larger than those of Smut ; and instead of being plain and smooth as in that species, their surface is beautifully reticulated. The seeds contained in the spore cases are of a greasy, oily nature, and consequently adhere to the skin of the sound grains, so that the disease may be propagated at any time by innoculation or contagion. One grain of wheat contains upwards of four millions of spores ; but the number of seeds contained in these is beyond calculation. "When bunted wheat is ground accidentally with healthy, it gives the flour an exceedingly nauseous taste, and is no doubt injurious to the health in proportion to the quantity introduced. Another species of " blight" is known to farmers as Rust, or Red-robin. It is called by botanists Trichobasis rubigovera. Under certain circumstances it breaks out on the young blades of the wheat early in the spring , later in the season it will then attack the ear, even after the grain is formed. So long as it is confined to the blade, or stalk, it is comparatively harmless. The grain continues to swell in spite of it, and though the flag seems to droop and look yellow, a few dry, sunshiny days — by drying up the moisture in which it luxuriates — will arrest its progress, and restore healthiness to the crops. A long continuance of warm, damp weather, will cause it to break out to such an extent, -that a person walking through the field will be completely painted with its rusty powder, and in the end, the quality and quantity of both grain and straw will be seriously affected. In appearance, the corn Rust is an eruption of reddish-yellow powder. Its microscopic character is somewhat different from that of Smut and Bunt. Its spores grow from a mycelium or spawn thread like Bunt, but unlike that species, they are furnished at their base with a short thread-like foot-stalk, attaching them to their matrix, which at length falls away. They are exceedingly beautiful and delicate objects, and will amply reward the most careful microscopic examination. The fourth and worst species of blight with which we are troubled, is Mildew, caused by the fungus Puccinia Graminis. Mildew is derived from the Saxon words, Mehl-tban, meaning meal dew. It makes i its appearance in the corn fields in the beginning of summer, and first takes possession of the lower green leaves, which become sickly ; it then breaks out on the corn stalk, in rusty, blistered patches. Examined under the microscope, these patches resolve themselves into dense masses of round, one-celled spores, rising from the midst of delicate branched threads, which insinuate themselves in a complete net-work amongst the cells of the diseased leaves. At this stage of growth, Mildew presents so close a resemblance to Kust, that it is regarded by some as a mere form of it. A month or two later, however, it presents some differences. Not only is it more abundant than before, but it changes its color from a rusty red to a dark brown, and its spores become pear-shaped, each tapering gradually into a stalk, and also two-celled, each cell filled with granular contents. Finally, when the corn is nearly or fully ripe, the straw and the culm are profusely streaked with black spots, ranging in length from a minute dot to an inch. This is tbe fully developed Mildew. It is common to all the cereals and many of the grasses grown in this country. Its effect seems to be to intercept the sap intended to nourish the grain, which consequently becomes shrivelled and deficient in nutritive matter, yielding a super abundance of inferior bran. One acre of mildewed wheat will produce seeds sufficient to inoculate all the wheat grown in the colony. The atmosphere is charged to an inconceivable extent with them; the soil of every field is sown thick with them. ! Almost every grain of corn, wheat, or barley, from the finest samples, is found, J under the microscope, to have one or more seeds adhering to its husk. It is indeed a fortunate circumstance that they refuse to grow except in stagnant, ill drained places, and under peculiar conditions of warmth and moisture. On the virgin soils of new colonies they spread with the same rapidity as on the exhausted fields of old countries. A Member of the "Western Disteict Farmers' Club.