Diseases of glasshouse plants (1923) Diseases of glasshouse plants diseasesofglassh1923bewl Year: 1923 68 DISEASES OF GLASSHOUSE PLANTS a fact that is well known to nurserymen. The disease thrives upon rich composts, and such are therefore more favourable for it than loam alone. Causal Organisms.—Considerable experience of this disease has shown that it is caused mainly by three fungi —Rhizoctonia solani Kuhn, Phytophthora cryptogea Pethy- bridge and Lafferty, and Phytophthora parasitica Dastur. The first is less common than the latter two fungi, which are consequently the most important cau
Diseases of glasshouse plants (1923) Diseases of glasshouse plants diseasesofglassh1923bewl Year: 1923 68 DISEASES OF GLASSHOUSE PLANTS a fact that is well known to nurserymen. The disease thrives upon rich composts, and such are therefore more favourable for it than loam alone. Causal Organisms.—Considerable experience of this disease has shown that it is caused mainly by three fungi —Rhizoctonia solani Kuhn, Phytophthora cryptogea Pethy- bridge and Lafferty, and Phytophthora parasitica Dastur. The first is less common than the latter two fungi, which are consequently the most important cause of the disease. Rhizoctonia solani is the sterile stage of a spore-bearing fungus, Corticium vagum B. & C, var. Solani Burt. The young hyphae produce branches which generally leave the mother fila- ment at an acute angle and subsequently turn and He parallel to it. The branch is constricted near the point of origin and a cross wall is formed a httle beyond the constriction (Fig. 5). In age, the angle of branching becomes more nearly a right angle, and the hjrphse turn first yellow and then a deep brown colour. Resting bodies or sclero- tia, capable of resisting abnormal conditions, are produced, being at first small, soft white masses, but later they increase in size and turn dark and hard. The Corticium stage, which forms later, shows as an ashy-grey tufted layer at the base of the stem, from which innumerable small spores are produced. These are easily carried by the wind, and so disseminate the disease. This stage is not always produced, and indeed requires special cool, moist conditions for development. Rhizoctonia solani is commonly found in rich soils, where it constitutes an important disease of many plants. Phytophthora parasitica Dastur (16) was first described by Fig. 5. Hyphte of Rhizoctonia solani.
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