. Diseases of glasshouse plants. Greenhouse plants; Plant diseases. 138 DISEASES OF GLASSHOUSE PLANTS calla lily (Richardia) have been troubled by a disease which threatened to exterminate their entire stock. On some nurseries its hold became so strong that it was impossible to grow arums, and the whole of the stock had to be burnt. Only after an interval of several years was it possible to cultivate this plant again. The disease generally shows itself about January, after the first lot of blooms has been gathered. First symptoms consist of a withering of the leaf apex and a desiccation of the
. Diseases of glasshouse plants. Greenhouse plants; Plant diseases. 138 DISEASES OF GLASSHOUSE PLANTS calla lily (Richardia) have been troubled by a disease which threatened to exterminate their entire stock. On some nurseries its hold became so strong that it was impossible to grow arums, and the whole of the stock had to be burnt. Only after an interval of several years was it possible to cultivate this plant again. The disease generally shows itself about January, after the first lot of blooms has been gathered. First symptoms consist of a withering of the leaf apex and a desiccation of the entire margin. The desiccation spreads as blotches from the margin and the diseased leaves die prematurely. The plants come to a standstill, do not readily produce more flowers, and do not react to feeding. An examination of the roots shows them to be brown, soft, and watery. The rot spreads from the roots back into the pseudo-corm (Fig. 38), becoming worse as the season advances. Quite commonly the foliage appears to recover, but soon goes back to the diseased ap- pearance. This recovery corresponds to the production of clean roots, but as these are attacked in turn so the fohage suffers. The disease is of bacterial causa- tion, and isolation has yielded a bacillus indistinguishable from B. carotovorus Jones. Townsend has also described a soft rot of the calla in America due to B. aroidece, which is closely related to B. carotovorus, but our isolations appear to differ from B. aroidece Towns. Certain methods of control have been devised which up to the present have yielded satisfactory results (7). The general method is as follows : After the plants have been allowed to " dry off " they are shaken out of the pots and all soil removed. The adventitious roots are. Fig. 38. Arum dlgease caused by Bacillus carotovorus showing {dIseaBed corm and Please note that these images are extracted from scanned page images that may have been digitally enhanced for readabil
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectplantdi, bookyear1923
