52 APPLIED ENTOMOLOGY 



The Lime-sulfur wash is used both as a strong spray against insects 

 during their dormant season, and as a weaker one for general purposes 

 during the summer. In the latter case, besides being a contact insecti- 

 cide, it has a little value as a stomach poison. It cannot safely be used 

 on stone fruits or potatoes, however. 



This material must be kept in air-tight containers as it decomposes 

 on standing when exposed to the air. A film of some vegetable oil over it, 

 for partly filled containers, will give this protection. It should not be 

 allowed to freeze. 



For stone fruits where a summer treatment seems necessary, self- 

 boiled lime-sulfur may be used. This is. prepared by slaking 8 lb. of 

 fresh stone lime in a barrel, in enough water to nearly cover it. Eight 

 pounds of fine sulfur should be gradually added to this, as soon as the 

 lime begins to slake, running the sulfur in through a sieve to break up any 

 lumps. This mixture should be constantly stirred and more water 

 added to form first a thick paste, then gradually a thin one. The heat 

 produced by the lime in slaking will cause the mixture to boil for several 

 minutes. When slaking is at an end, cool the mixture rapidly by adding 

 considerable water, then strain into the pump to remove lumps of lime, 

 but working any lumps of sulfur through the strainer; then dilute with 

 water to a total of 50 gal. 



Dry Sulfur Compounds. — These substances have recently appeared 

 in competition with the lime-sulfur wash, the advantages claimed for 

 them being ease of handling, reduction of shipping charges, no deteriora- 

 tion on standing, and equal efficiency at lower cost. 



These substances are sulfid combinations with either potassium, 

 sodium, barium or calcium. The amount of sulfur present varies greatly 

 in different brands. They do not contain as much of the polysulfids 

 which appear to be the actual insecticides of the lime-sulfur wash as the 

 liquid wash, and even the amount of sulfur present in them, after the 

 addition of water according to directions, is less than in an equal quantity 

 of the wash, so that basing efficiency on the amount of sulfur, regardless 

 of its form, the amounts of these dry materials would have to be greatly 

 increased to equal that of the wash, and would therefore seriously increase 

 their cost. At the present time their value cannot be considered as 

 having been finally settled though in many cases field tests of them have 

 given good results. Continued studies and tests of these materials are 

 needed to determine their real value. 



Sulfur. — This substance in the form of a very fine powder, can be 

 dusted over plants for the destruction of red spiders and other mites, 

 or it may be made into a paste with soapy water, using 10 lb. of sulfur 

 and 2 lb. of soap in 50 gal. of water, and applied as a spray Its use is 

 rather limited and its actual value somewhat questionable in many cases. 



