AN OIDIUM MILDEW ON CARNATIONS. 



229 



it is not yet possible to refer the carnation fungus to its proper species. 

 The probabilities are that it represents a species which normally 

 occurs on other plants, but which is in process of extending its range 

 of hosts. 



Treatment. — As soon as the nature of the disease was determined, 

 steps were taken to combat it. All the plants were at once sprayed 

 with a copper-ammonia mixture,* and at the same time the pots 

 and stands were as far as possible similarly disinfected. Thereafter, 

 for the remainder of the summer, the plants were sprayed regularly 

 every week or ten days. 



It was at first intended to try a number of different sprays, but 

 the effects of the first two or three dressings with copper-ammonia 

 mixture were good enough to justify the continued use of this parti- 

 cular spray, and, as there were no means of isolating infected plants t 

 considerable risk would have attended a trial with other sprays. 



Two per cent, lime-sulphur mixture was, however, tried on a 

 few plants. It was thoroughly effective as regards checking the 

 fungus, but the plants were so disfigured by the tenacious white 

 deposit that the dressing was not repeated. 



An occasional spraying during the early autumn sufficed to keep 

 the plants clean, and during the winter and the present season it has 

 only been necessary to pick off the few mildewed flower -buds which 

 have appeared and to paint over with copper-ammonia mixture such 

 spots on the leaves as could from time to time be discovered. 



So far as it is possible to see, therefore, the disease has been effec- 

 tively controlled by repeated sprayings, and this course of treatment 

 can be recommended in the case of similar outbreaks, with considerable 

 confidence. The superficial habit of the mycelium makes it an easier 

 subject to deal with than is the case with deep-seated parasites. It is 

 probable, too, that the fungus has not yet become thoroughly con- 

 firmed in its parasitic habit on this particular host plant. Indeed, 

 it is difficult to account on any other grounds for the comparative 

 ease with which it has been subdued. 



* Stock mixture made up as follows: — if lb. crystallized copper sulphate, 

 1 quart strong ammonia, 2 h gallons water. Half a pint of this mixture diluted 

 to 4 gallons with water before use. 



