. Fig. 41.—Sclerotia (the black bodies) of the cottony-mold fungus developing apothecia (the trnmpet-shaped, toadstool]ike protuber- ances) in which spores of the fungus are produced at the surface of the ground. (Natural size.) (From Ext. Cir. 118.) only become infected by spores developed from sclerotia in the soil and blown about by the wind. The fungus may become very abundant and kill almost any kind of plant in certain spots or areas of soil where there is a good deal of moisture and dense vegetation, but it does not always persist long enough to attack other plants growing later in the
. Fig. 41.—Sclerotia (the black bodies) of the cottony-mold fungus developing apothecia (the trnmpet-shaped, toadstool]ike protuber- ances) in which spores of the fungus are produced at the surface of the ground. (Natural size.) (From Ext. Cir. 118.) only become infected by spores developed from sclerotia in the soil and blown about by the wind. The fungus may become very abundant and kill almost any kind of plant in certain spots or areas of soil where there is a good deal of moisture and dense vegetation, but it does not always persist long enough to attack other plants growing later in the same places. Sometimes in greenhouses the soil becomes permanently infested with the cottony-rot fungus and must either be changed or disinfected before susceptible plants can be grown again. Treatment with steam or with formaldehyde (see "Damping Off," p. 92) is effective. CURLY TOP This disease, which is best known in connection with the sugar beet (p. 15) and tomato (p. 82), sometimes attacks a variety of other plants under especially favorable circumstances. Beans, cantaloupes, celery, cucumbers, geraniums {Pelargonium), mangels, nasturtiums, pansies, peppers, squash, and zinnias are examples of this. This is a virus dis- ease which is spread from plant to plant by a small insect, the beet leafhopper, Eutettix tenellus. (See Extension Circulars 87 and 95).
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Keywords: ., bookcentury1900, booksubjectagriculturalpests, booksubjectplantd
