Fungi and fungicides; a practical manual, concerning the fungous diseases of cultivated plants and the means of preventing their ravages . 53). It contains numerous references to theEuropean literatuie of the subject. An earlier article,by Professor W. G. Farlow, will be found in the reportof the Massachusetts State Board of Agriculture for1876-77 (p. 164). The Onion Spot Disease Vermicularia circinans This is a fungus which has been described as inju-rious to white varieties of onions after they are starts in the field on part of the bulbs ; these producemany spores, by means of whi
Fungi and fungicides; a practical manual, concerning the fungous diseases of cultivated plants and the means of preventing their ravages . 53). It contains numerous references to theEuropean literatuie of the subject. An earlier article,by Professor W. G. Farlow, will be found in the reportof the Massachusetts State Board of Agriculture for1876-77 (p. 164). The Onion Spot Disease Vermicularia circinans This is a fungus which has been described as inju-rious to white varieties of onions after they are starts in the field on part of the bulbs ; these producemany spores, by means of which it is propagated in thebins when the conditions are favorable; that is, whenthe atmosphere of the storage room is warm and moist. 158 FUXGl AXD FUXGICIDES The disease appears in the field as a blackish growth onthe outer bud scales. It is not noticeable at first, andwhen closely examined will be seen to consist of a cen-tral dot or ring, surrounded by larger rings. Duringdamp weather the black growth develops rapidly, some-times in the form of circles, and sometimes simplyspreading without circles, as in Fig. 60 a. AYhen the dis-. ly-^c II \ a FIG. , Spot (liseafe of onions; b, spores. ease first appears it only affects the outer scales, butlater it penetrates deeper and causes rot. When highly magnified tlie black specks on thebulb scales resemble Fig. 69 b. Each consists of a massof mycelium having long, black, pointed bristles, aroundthe bases of which the small, slightly curved spores areproduced in great numbers. These spores are easilyblown upon surrounding bulbs, where they may germi-nate and start the disease again. Treatment.—One of the best safeguards againstthis disease is to put dry onions in dry bins, in cool anddry storerooms. The onions should not be allowed to THE OKION SPOT BISEASi: 159 heat at all, and bins which have contained diseasedonions should be disinfected by spraying or dusting withsome fungicide before they are again used. It has beensuggest
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