. Florists' review [microform]. Floriculture. AOODST 4, 1921 The Rorists' Review 27. GERANIUM LEAF-SPOT. How the Disease Spreads. The presence of red spicier, white fly, pallid mite or other pests has little or nothing to do with the spread of leaf-spot on geraniums, but the method of watering has much to do with it; the watering, in fact, frequently is the chief agency in carrying the disease germs from one plant to another. Such, in substance, is the conclusion reached at the Maryland Agricultural Experi- ment Station, after an elaborate series of experiments. The tests proved that the leaf-
. Florists' review [microform]. Floriculture. AOODST 4, 1921 The Rorists' Review 27. GERANIUM LEAF-SPOT. How the Disease Spreads. The presence of red spicier, white fly, pallid mite or other pests has little or nothing to do with the spread of leaf-spot on geraniums, but the method of watering has much to do with it; the watering, in fact, frequently is the chief agency in carrying the disease germs from one plant to another. Such, in substance, is the conclusion reached at the Maryland Agricultural Experi- ment Station, after an elaborate series of experiments. The tests proved that the leaf-spot fuiigus, scientifically called Cercospora brunkii, does not en- ter the punctures made in the leaves by pests, that direct transfer of the insects from infected to uninfected plants fails to produce the disease, and that the rate of spread of the disease is not materially increased by the pres- ence of the insects, even if they are so numerous as to disfigure the leaves with punctures and the resultant stigmonose. On the other hand, it was clearly dem- onstrated that in watering with a hose, if the stream of water is driven through the leaves in a direction parallel with the surface of the bed, the leaf-spot germs are quickly and surely conveyed from the diseased to the sound plants. How to Identify Leai-spot. Since the leaf-punctures made by in- sects, with the consequent stigmonose, have a greater or less resemblance to leaf-spot, it is important to be able to distinguish between these different blemishes of the foliage. The leaf- spots, says a bulletin recently issued by the Maryland Experiment Station, "vary from about a millimeter in di- ameter [a little less than one-twenty- fifth of an inch] to several millimeters. Infected areas examined by transmitted light are characterized in the stages by the appearance of small, dark, •opaque spots, which are later surround- ed by a raised, transparent border. The elevated rim is particularly notice- able in dead
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Keywords: ., bookcentury1900, bookdecad, booksubjectfloriculture, bookyear1912
