RED RUST IN WHEAT.

Waikato Times, Volume XXI, Issue 1729, 4 August 1883, Page 6

RED RUST IN WHEAT.

(Prom Macivor's Farmers' Annual.) The great en«my of the colonial wheat-grower — " Bed Rust "—is a minute parasitic fungus, having habits of life as definite in character as those of the plants it feeds on. Eg NATURE AND DEVELOPMENT OP THE lIUST ff?,UW • ?I<V> FDNGUS. liThe small black or dark-brown spots and .streaks [mildew] so frequently noticed on grain stubbles, each consist of a multitude of oval-shaped cells, or spores, which have developed from the interior and ruptured the epidermis, or skin of the straw. Had the entire plants been left on the ground the leaves as well ,as the straw would have shown' these patches and lines. The spores of mildew are invariably double, that is, there are two, end to end, at the extremity of each

slender thread. Fig. 1 a shows one of the double spores separated from its neighbors, and highly magnified. The germination of the spore is .shown in H, which consists in the bursting of the outer covering of the spore, and the production of the irregular filaments c upon each of which, in a few hours, small ovate bodies d d, are developed, which soon become detached. Four or five of these small bodies, or spores, are formed from the old one ; this occurs in the spring whenever the winter spore (the double spore, or mildew) can get the necessary warmth and moisture. One of the small single spores d d is shown/much magnified. These spores are carried by the wind, or other agency, to the leaves o£ the Barberry, and if there are no Barberry bushes, probably to some other plant, when they germinate, forcing their filaments or rootlets into the tissues of the leaf, and in the cource of a day or two a yellow spot is formed on the

Barbery leaf. Fig. 2 a, and shortly after a number of " cups " are formed from the bursting of the epidermis of the leaf, (hying to the Close proximity to each other in which these cups occur they are well termed "cluster cups " which are shown somewhat magnified as b, and a single one more highly as c, with a side view of the same as d. The lower part of Fig 2. presents a still more highly magnified view of a cross section of one of the "cups" showing the ruptured epidermis of the leaf at c and/, between which the cup h goes down into the interior of the leaf g. The cup is filled with spores which are arranged m chains or and break away from their attachment h and are carried away by winds sometimes to a distance of many miles. These spores soon find their way to growing wheat, upon the leaves and stems of which they germinate and send their filaments through the tissue of the plants. In course of a little time these filaments collect at certain places immediately within the surface of the wheatleaf and, in enlarging, rupture the epidermis.

Fig. 3 a a. Myriads'^ yellowish-brown spores are rapidly formed and give the well-known " rusty " appearance to the plants affected. This stage ot the fungus is known as uredo. Fig. 3 shows a cross-section through one of these urcdo spots, with the spores h, crowded together each on a slender stalk which holds it to the filaments in the tissues of tKe leaf c. Prom these same filaments, and in the same spots, the brown-black spores of mildew appear later in the season and complete the lircle ot changes of this only too interesting iungus. The foregoing description of the rust fungus •should convince farmers that the parasite cantnot originate spontaneously. It is a plant in the true meaning of the term, and therefore cannot be developed except^ from its own seed however the latter may have found its way on to a particular farm. •