. Fig. 6.—Black stem rust on wheat. The ragged-edged scars are the black pustules which bear the spores by which the rust fungus overwinters. appear in June and from that time on increase in number until the wheat is ripe. Soon after appearing, they rupture the stem tissue, exposing the powdery, red mass of summer spores. Frag- ments of the wheat epidermis adhere to the sides and ends of the pustules, giving them a ragged appearance, especially at the ends. This ragged appearance and the length of the pustules are two characteristics which distinguish black stem rust from leaf rust. Individual
. Fig. 6.—Black stem rust on wheat. The ragged-edged scars are the black pustules which bear the spores by which the rust fungus overwinters. appear in June and from that time on increase in number until the wheat is ripe. Soon after appearing, they rupture the stem tissue, exposing the powdery, red mass of summer spores. Frag- ments of the wheat epidermis adhere to the sides and ends of the pustules, giving them a ragged appearance, especially at the ends. This ragged appearance and the length of the pustules are two characteristics which distinguish black stem rust from leaf rust. Individual pustules may be a quarter inch or more long, and in heavy infections two or more may run together and form streaks. As wheat nears maturity, the rust fungus forms the black pus- tules filled with the black spores from which the disease gets its name. Life History.—The final effort of the black stem rust fun- gus, as the wheat plant nears maturity, is the production of its
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Keywords: ., bookcentury1900, bookcolle, bookpublisherurbana, booksubjectgrain
