THE CAMPHOR SCALE 



17 



When spring or summer sprays are necessary, the best results will 

 be obtained if applications are made about 57 days after the appear- 

 ance of the first newly settled nymphs in the spring or about 36 days 

 after the beginning of emergence of the second-brood crawlers. Emer- 

 gence of the second brood begins in June in years when normal tem- 

 peratures have prevailed. 



Cheap lubricating oils of 100 to 200 seconds Saybolt viscosity may 

 be used in preparing the emulsions, or one of the commercial emul- 

 sions on the market may be purchased. In the latter case the manu- 

 facturer's directions for use should be followed. 



FUMIGATION 



The best means of controlling the camphor scale on nursery stock 

 or other plants that are to be shipped is by fumigation with hydro- 

 cyanic acid gas. For this purpose a double-walled box or other 

 suitable container should be provided. This box should be large 

 enough to allow ample room for the plant material and pot or other 

 earthen vessel in which the gas is to be generated, as nearly gastight 

 as possible, and fitted with a door that can be quickly and tightly 

 closed. 



The foliage and tender twigs of all plants should be thoroughly dry 

 before fumigation is started, to avoid undue risk of burning, and the 

 plants should not be exposed to direct sunlight for several hours 

 before and after treatment. All boxes or other containers of plant 

 material should be open to enable the gas to reach all surfaces of the 

 stem and leaves in full strength. 



An exposure of 1 hour is recommended at the following tempera- 

 tures and dosages (per 1,000 cubic feet) : 



At 80° F. and above: 



.do. 



Sulphuric acid- 

 Sodium cyanide 



ounce avoirdupois. 



1% 



Below 80° F. : 



Water fluid ounces. 



Sulphuric acid do__. 



Sodium cyanide 



ounce avoirdupois. 



3 



iy 2 



The acid should be poured slowly into the water, in an earthen pot 

 or jar, the cyanide, previously weighed, gently dropped into this 

 solution, and the door of the fumigating box immediately closed. 

 (Do not pour water into the acid, or the violent reaction may spatter 

 the mixture and cause dangerous burns.) Commercial sulphuric 

 acid that tests at least 65° Baume, or 1.84 specific gravity, should be 

 used. The sodium cyanide should be practically free from chlorine 

 and should contain not less than 51 percent of cyanogen. These dos- 

 ages will kill practically all the scales, but at temperatures below 

 80° F. even the increased quantity of cyanide has failed to kill all 

 the eggs. Neither can the 1-ounce dosage be used with all plants, since 

 some will be injured by this concentration of gas. 



In greenhouse fumigation it is difficult to give a general dosage 

 schedule because of the variation in susceptibility between different 

 plants, and the loss of gas through leakage. When only a few plants 

 are to be treated, the use of a fumigating box avoids these difficulties. 

 If it is desired to fumigate the entire greenhouse, the proper strength 

 to use will depend on the tightness o-f the house and the susceptibility 

 of the plants to be treated. 



