Fungoid pests of cultivated plants / by M.C. Cooke.

  • Mordecai Cubitt Cooke
Date:
1906
Catalogue details

Licence: In copyright

Credit: Fungoid pests of cultivated plants / by M.C. Cooke. Source: Wellcome Collection.

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    Sacc. Syll. vii. 2174; Cooke Hdbk. No. 1G2G; Garcl. Chron. 1876, 175, 361, fig. 72 ; Cooke M. F. 198 ; Grove Journ. Bot. 1888, p. 274 ; Plowr. Brit. Ured. 158. Violet Rot-mould. Peronospora Viola (I). Bary), PI. VI. fig. 24. Amid all tlio vicissitudes of the Violet crop it has hitherto suffered little serious injury from the rot-mould, which is of close kindred to the Potato disease mould. It has appeared, and is not uncommon, on wild plants, and has recently invaded the Violet and Pansy under cultivation. The tufts of the mould are effused on the foliage, and although white are not particularly conspicuous ; the threads are collected in little bundles, growing erect, and are many times divided in the upper portion into forked branches, with the final branchlets awl-shaped and bent backwards. The conidia are elliptical, growing singly at (22-27 x 15-19 y) the tips of the branchlets, but with a slight tinge of violet in their colour. It is assumed that resting spores are produced, as in other rot-moulds, hut they have not yet been detected. (See Introduction, p. 3.) Plenty of air, and not too much water, retard the spread of the disease. Another rot-mould (Peronospora megasperma) has been found on Viola tricolor in the United States. Sacc. Syll. vii. 838 ; Berlese leones, t. xlii.; Mass. PI. Dis. 80; Cooke M. F. 235 ; Grevillea, iv. 109 ; Mass. B. F. p. 121. Violet White Mould. Bamularia lactea (Desm.), PI. I. fig. 23. This common little white mould on Violet and Pansy leaves does not much trouble the cultivator, since it has preference for the wild plants. White orbicular spots appear on the leaves, circumscribed by a brown line, three or four spots being usually present on one leaf. The mould gives a mealy appearance to the spots, as if they had been powdered with flour, and principally on the under surface. The mould itself is a very simple structure, consisting of rather twisted short threads (30-G0 y long), without branches, bearing at their tips the oblong or spindle-shaped conidia (8-10 x 2-8 y). Occasionally two or three of the conidia will be met with attached to each other, end to end, so as to form a short chain. It has been suspected that many of the species of this genus of moulds are only the naked conidia of some higher form of fungus, as has been proved in a few cases. The present mould is known, not only in Britain, but also in France, Germany, Bohemia, Austria, and Italy. It seems to be amenable to fungicides if taken in time. Sacc. Syll. iv. 979 ; Journ. Iloy. Agr. Soc. lxi. (1900), p. 735 (sub Ovularia lactea); Journ. B.H.S. xxvi. (1901), p. 198; Grevillea, iv. p. 109. Another species, Bamularia agrestis, with larger and sometimes septate conidia, has occurred on Violet and Pansy leaves in Italy.
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