SPRAYING AND FUMIGATING. 535 



loss has been occasioned in some instances in Florida by 

 spraying in May. 



It may be stated that fumigation is not effective 

 against the purple mite, the rust mite and similar insects. 

 They must be sprayed, though against the rust mite in 

 Florida, flowers of sulphur applied with a powder gun has 

 proved effective. The sulphur must be applied in the 

 morning when the trees are damp with dew. To keep the 

 fruit bright, by destroying the rust mite, sprays must be 

 applied once about every three weeks during the summer 

 and fall months. 



FUMIGATING. 



For fumigating citrus trees hydrocyanic-acid gas gen- 

 erated by treating potassium cyanide with diluted sul- 

 phuric acid is used. The gas is liberated under a tent 

 which covers the tree. 



Many different kinds of tents are in common use. 

 Among these may be mentioned the sheet hoop and bell 

 tents (Plate 35). The style of tent used is governed in a 

 large measure by the size of the trees, but the sheet tent 

 is probably the most useful of all. For small trees, up to 

 ten or twelve feet, the hoop tent is very serviceable. 



Tents and Treatment. The following is from the pen 

 of Prof. C. W. Woodworth, in regard to the materials for 

 making tents and the treatment which must be given to 

 render them gas-tight. 



"Common duck is now uniformly employed for mak- 

 ing the tent, most of them being made of the 8-ounce can- 

 vas, such as is used for light sails. The cloth is lapped and 

 double-sewed in the same manner as for tents or sails. 

 The edge is usually simply hemmed, but some bind it with 

 rope. Whenever permanent rings for handling are at- 



