. Minnesota plant diseases. Plant diseases. 376 Minnesota Plant Diseases. not unlike a smut mass. The spore mass is black and powdery and the spores are, in general features, similar in appearance to the winter spores of the leaf rust. Infected plant parts should be destroyed before the spores have a chance to disperse. The Indian turnip leaf rust [Uromyces caladii (Schw.) Farl.]. This rust is sometimes found on cultivated Aroids. (See Dis- eases of Wild Plants.) Golden-rod and aster leaf rust [Coleosporium sonchi-ar- vensis ( Pers.) Lev.]. The g-olden-rod rust is an exceed- ingly abundant dis
. Minnesota plant diseases. Plant diseases. 376 Minnesota Plant Diseases. not unlike a smut mass. The spore mass is black and powdery and the spores are, in general features, similar in appearance to the winter spores of the leaf rust. Infected plant parts should be destroyed before the spores have a chance to disperse. The Indian turnip leaf rust [Uromyces caladii (Schw.) Farl.]. This rust is sometimes found on cultivated Aroids. (See Dis- eases of Wild Plants.) Golden-rod and aster leaf rust [Coleosporium sonchi-ar- vensis ( Pers.) Lev.]. The g-olden-rod rust is an exceed- ingly abundant disease upon almost if not all of the spe- cies of golden-rod, asters and their allies, found in the state. The bright orange-red summer spores appear in great numbers chiefly on the under surface of the leaves, and form a bright- colored powder. Often the en- tire lower surface of the leaf will be covered with the spore groups. The winter spores arise later in light-colored, crust-like groups. These spores remain attached to the leaf throughout the winter and germinate in the following spring. They do not germi- nate in exactly the usual way for rust winter-spores for they do not send out a thread in the ordinary manner. Four spores are, however, produced from each winter spore and each is borne on a stalk which comes directly from the spore which has been previously divided up into four cells by cross walls. The cluster- cup spores are probably formed on some coniferous trees. Cultivated plants may be treated with ammoniacal copper car- bonate, early in spring, and the treatment should be continued every two to four weeks. (Fig. 205.). Fig. 201.—Leaf rust of roses. 1. Rose branch and leaves infected with cluster- cup stages of the disease. 2. Leaf with clusters of winter spores. 3. Win- ter spores. 4. Summer spores. 3 and 4 highly magnified. After Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability
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