. Fungous diseases of plants : with chapters on physiology, culture methods and technique . Fungi in agriculture. PHYCOMYCETES 159 been devoted to the cultivation of melons or of cucumbers, especially for the pickling trade. Nevertheless, it is now a very constant disease in greenhouse-grown cucumbers. The fungus has been found on most of the cultivated species of the Cucurbitaceae, or gourd family, such as cucumbers, musk- melons or watermelons, squash, pumpkins, gherkin, and also upon the star cucumber, Sicyos angtdatus, and a few other wild species. Symptoms and effects of the disease. The
. Fungous diseases of plants : with chapters on physiology, culture methods and technique . Fungi in agriculture. PHYCOMYCETES 159 been devoted to the cultivation of melons or of cucumbers, especially for the pickling trade. Nevertheless, it is now a very constant disease in greenhouse-grown cucumbers. The fungus has been found on most of the cultivated species of the Cucurbitaceae, or gourd family, such as cucumbers, musk- melons or watermelons, squash, pumpkins, gherkin, and also upon the star cucumber, Sicyos angtdatus, and a few other wild species. Symptoms and effects of the disease. The effect of this dis- ease upon the host, that is, upon the cucumber, have been very clearly presented by Stew- art as follows : The leaves show yellow spots which have no definite outline. If the weather is warm and favorable for the disease, these spots enlarge rapidly and run together so that the whole leaf becomes yellow and soon dies and shrivels like a leaf killed by frost. If the weather is cool, the yellow spots spread less rapidly. In the latter case the central portion of the yellow spots becomes dead and brittle and of a light-brown color. . The disease invariably begins with the oldest leaves and proceeds toward the tips of the vines. Hence the disease appears to proceed from the center of a hill outward. In a field recently attacked, the center of every hill will be clearly marked by a cluster of yellow leaves, so that the rows may be plainly seen clear across the field, even though the plants are large and cover the ground. Affected plants continue to grow at the tips and put out new leaves, and it is interesting to note how the disease follows at a distance of about four or five leaves behind the growing tip. After the disease is once thoroughly established, very few cucumbers are produced, although the plants may continue to flower profusely. The few cucumbers which are formed grow slowly and become misshapen so that they are unsaleable. . Of the total shortage of
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Keywords: ., bookauthorduggarbe, bookcentury1900, bookdecade1900, bookyear1909
