OCR Text |
Show BEAN RUST DISCOVERED AMONG COMMON PLANTS Destructive Disease, Similar in Character to that Which Often Attacks Wheat Has Three Stages By L. H. Pammel. For a number of years we have lad under observation a rust occurring occur-ring rather abundantly on the common com-mon bean, especially the pole bean. During the summer of 1908 specimens of the rust were sent In by a correspondent corre-spondent from Grlnnell, la., where It wa3 common and destructive. During the fame season the cluster-cup stage was collected by one of us at La Crosse, Wis. The finding of the cluster-cup stage i on the cultivated bean has not hereto- ' fore been mentioned by American writers on economic fungi, although It is commonly observed on some of the wild beans. That this stage has been found Is of especial interest as it accounts ac-counts for the source of infection of the cultivated bean. This bean rust in its development is not unlike the common wheat rust, which has three stages. In the case of The number of the cups (aecidia) varies from 4-6 in the smaller spots to "0-25 in the larger spots. They arr-pale arr-pale In color, the peridial cells beinj colorless. The spores are spherical tc elliptical 10-26 u in diameter, minutelj roughened. The spermogonia are or the upper surface of the leaf, minute; the spermatia small, spherical. The uredospores occur in spots which are at first roundish, but later, becoming confluent, for irregular patches fre-quentyl fre-quentyl quadratic in form; the sori or pustules of the fungus occur on both surfaces of the leaf, and not infrequently in-frequently on the pod and peduncle, varying from a few to many in a spot. The uredosori which contain the summer sum-mer spores are yellowish brown and appear during the summer. While usually hot one of the mos1 troublesome diseases of the bean, it occasionally becomes so severe as tr cause serious loss. It is recorded b? 8 J Bean Rust, Uromyces appendiculatus. a, Cluster Cup Stage; b, Uredo Spores; c, Teleutospores. wheat rust, the first stage is upon the barberry, but in the case of the bean all three stages occur upon the same host plant. The aecidium or cluster-cup stage occurs upon the under surface of the leaves in definite spots. The color of the leaf in the vicinity of the spots does not differ materially from the t-o'or of the remainder of the leaf. Pautmel and by Beach as destructive to late varieties, particularly to the wax bean. Careful selection of seed grown in regions where the rust is not found, the burning of old bean leaces likely to contain winter spores, and the destruction de-struction of wild beans in the neighboring neigh-boring grounds are the best means to hold the bean rust in check. |