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OCTOBKU 13. 1904. 



V. 



The Weekly Florists' Review* 



J 009 



Home Plant of Clarke Bros., 'with a Glimpse of Portland, Ore., in the Distance. 



THE CALLA DISEASE. 



The Bureau of Plant Industry of the 

 Department of Agriculture has recently 

 issued a bulletin on the soft rot of the 

 calla lily which will be of interest to 

 every calla grower, if not of as great 

 practical assistance as had been hoped 

 for by those who knew the work was in 

 preparation. There is no doubt that the 

 disease has brought great loss upon 

 growers and it is to be regretted that 

 four years of study by Prof. Townsend, 

 much of his work being done in the green- 

 houses of A. B. Garden, at Anacostia, 

 D. C, has not produced a more satis- 

 factory result. ' ' The successful treatment 

 of the diseased plants was considered im- 

 practicable, " writes the investigator, 

 ' ' and preventive measures were then re- 

 sorted to. Fresh soil was obtained, also 

 a new set of corms, but they were not 

 planted directly in the bed. All that 

 showed suspicious dark spots were dis- 

 carded; the remainder were started in 

 pots and transplanted. This made it 

 possible to discard all plants which 

 showed indications of disease after 

 growth began. ' That is simple but 

 not eminently satisfactory to the grower 

 who has paid good money for his bulbs 

 and found the disease to develop in a 

 very large proportion of them "after 

 growth began." 



Thcie is, however, much of interest 

 and value in the freely illustrated pam- 

 phlet of forty-four pages. The less tech- 

 nical parts follow: 



Introduction. 



Under favorable conditions the calla 

 lily has heretofore been one of the most 

 satisfactory plants produced either in 

 ithe open or under glass. In most parts 

 of the United States the calla will grow 

 out of doors and will live and thrive 

 from year to year even in the northern 

 latitudes, especially if the corms (bulbs) 

 are protected during the winter season. 



As a marketable product, however, it is 

 more profitable if grown under glass, 

 where under proper conditions the plants 

 may be forced and the flowers conse- 

 quently produced in great abundance at 

 the time when they will be in greatest 

 demand. It is under these conditions of 

 forced growth that the plants seem to be 

 most susceptible 'to disease. 



The profits which arise from calla 

 growing are derived either from the 

 sale of the corms or of the flowers, or 

 from both. A bed of a thousand corms, 

 for example, will under normal condi- 

 tions produce 5,000 flowers, which ordi- 

 narily will sell for about $1,000. (A 

 very sanguine estimate. — Ed.) The corms 

 are grown either in solid beds or in pots. 

 As a rule the best results both as re- 

 gards the size and number of flowers 

 produced are obtained from the solid 

 bed. 



There are several diseases to which the 

 calia is susceptible, but the most serious 

 one with which the growers have had 

 to contend- is the soft rot that forms 

 the subject of this bulletin. This dis- 

 ease has been reported from the Atlan- 

 tic to the Pacific and has caused enor- 

 mous losses to the growers, rendering 

 tlie production of this hitherto profitable 

 plant very uncertain. The soft rot of 

 the calla was brought to the attention 

 of the writer in the autumn of 1899, and 

 it has been under "his observation and 

 study since that time. 



Cause and Appearance. 



Upon examining microscopically the 

 decayed portions of the calla corms, my- 

 riads of bacteria were found to be pres- 

 ent. These were separated in pure cul- 

 tures and by repeated experiments were 

 shown to be the cause of this destruct- 

 ive disease. 



Several greenhouses where the disease 

 was reported to be present were visited 

 by the writer, who found the callas rot- 

 ting off usually at or just below the sur- i 



face of the ground, the disease sometimes 

 extending down into the corm, sometimes 

 upward into the leaves, and frequentlj 

 in both directions. Occasionally the 

 disease seemed to start in the edge of 

 the leafstalk, in tiie flower stalk, or in 

 some underground part of the conn, 

 though as a rule it started at the top 

 of the corm just above but near the 

 surface of the ground. It was also no- 

 ticed that the disease was worse and 

 spread more rapidly in those houses 

 where the callas were grown in solid 

 beds. 



When a diseased corm was cut open 

 it was found that there was a distinct 

 line between the healthy and the dis- 

 eased portion of the corm. The healthy 

 portion of the corm is firm and nearly 

 white, while the diseased part has a de- 

 cidedly brown color and is soft and wa- 

 tery. When the disease extends upward 

 into the leaves it is the edge of the 

 petiole that first becomes involved, the 

 affected part becoming slimy without im- 

 mediately losing its green color. As the 

 disease progresses the edges of the leaf 

 become pale, then brown. Pale spots 

 becoming brown then appear in other 

 parts of the leaf blade, and finally the 

 whole leaf becomes brown and dead. 

 Frequently the disease develops so rap- 

 idly that the leaf rots off at the base 

 and falls over before it has time to 

 lose its green color. . When the disease 

 has progressed far enough to attack the 

 flower stalk, the flower turns brown and 

 the stalk without having lost its color 

 and frequently without having decayed 

 upward more than a fraction of an inch, 

 eventually falls over. 



When the disease works downward 

 through the corm it sooner or later 

 reaches the roots, which become soft and 

 slintiy within, while the epidermis re- 

 mains intact, thus presenting the ap>- 

 pearance of thin-walled tubes filled with 

 a soft substance. When the disease be- 



