132 MASSACHUSETTS UORTICULTUH^L SOCIETY. 



rod or spike. These spikes were heated in the furnace and car- 

 ried rapidly through the house in an iron basket. The house is 

 (piiekly filled with tobacco steam. The manager assured me that 

 this method was cheaper, less injurious to the plants, and more 

 effective than the ordinary dry air method of tobacco fumigation. 

 They were cutting thirteen hundred buds a day from this house 

 and the thrift and beauty of the plants were remarkable. 



Scale insects are not so easily killed ; most of them will thrive 

 on tobacco smoke and ordinary sprays. We have, however, 

 found hydrocyanic acid gas very cheap and effective. It is a 

 deadly poison, and must be used with the greatest care. In 

 intelligent hands I am persuaded that it is the coming remedy for 

 this class of troubles. There must, however, be considerable ex- 

 perimenting and testing on the part of specialists before it comes 

 into general successful use. Not only does it quickly diffuse 

 through the air and speedily kill those who breathe it, but it also 

 kills the plants as well as the scales, if the dose is too strong. 

 Furthermore, plants are sensitive to it in very different degrees, 

 as Mr. A. F. Woods has shown, so that a dose which will not 

 harm one plant will kill another. In any given case it must be 

 determined in advance ; first, what is the ininimum dose for the 

 scale, and, second, that this dose will not harm the plants. When 

 these two facts have been ascertained the cubic contents of the 

 house to be fumigated must be accurately computed, and then 

 the proper amount of gas may be liberated after the house has 

 been closed as tightly as possible and the roof wet down to make 

 it still more air-tight. Details as to manufacture and liberation 

 of the gas, method of computing air space, and proper dose for 

 certain plants have been published recently by Mr. P. H. Dorsett, 

 in the '' Florists' Exchange," audi will not here describe them. 



By use of tliis method I have seen one hundred thousand 

 foliage plants (coleus, achyranthes, etc.) which were covered 

 with orthezia and ruined for transplanting freed from every 

 scale in twenty minutes' time at a trivial expense, and without 

 the least injury to the plants. I liave also known of the gas 

 being used successfully in violet houses for the destruction of 

 aphides. 



(3) Fungicidal Treatment. — Among fungicidal treatments may 

 be mentioned sulphur dusting, use of lime, use of mercuric chlo- 

 ride, hot-water treatment, and spraying with copper compounds. 

 Diseases amenable to one or other of these treatments are 



