Fungicides 449 



the same way that the ammoniacal sohition of copper car- 

 l)onate is used. Potassium sulfid is also especially efficient 

 as a protection against the powdery-mildews. 



Formalin. — Formalin is a very powerful germicide which 

 came into wide use about 1889. Its interest to the farmer 

 lies chiefly in its power to prevent the potato scab, onion 

 smut, and the various smuts of cereals. Full directions for 

 its use are given under special crops. 



This substance appears on the market under two names: 

 "Formalin" and "37 per cent formaldehyde." These sub- 

 stances are absolutely identical, and since the formaldehyde 

 solution is cheaper, owing to the fact that the word "For- 

 malin" is protected by patent, the customer will of course do 

 well to purchase the 37 per cent solution. 



Corrosive sublimate. 



Corrosive sublimate 1 part 



Hj'drochloric acid 2 parts 



Water 1000 parts 



This is employed chiefly as a seed disinfectant particu- 

 larly for black-rot of cabbage. It is intensely poisonous 

 and should be so regarded. 



Flowers of sulfur. — This substance is chiefly employed 

 as a specific for the powdery-mildews. See grape, p. 122. 



Proprietary fungicides. ^^^ — There are several proprie- 

 tary fungicides on the market. Of five tested on apples 

 in 1916, at the Illinois Experiment Station, four produced 

 serious foliage injury and more or less serious injury to fruit. 

 There are several commercial Bordeaux pastes on the market. 

 Wallace has shown that none which he tested remains in 

 suspension as well as fresh home-made Bordeaux mixture 

 (some are very poor in this respect) and that they are very 

 expensive if diluted to contain a copper content equal to that 

 of 4-4-50 Bordeaux mixture. 



Combined fungicide and insecticide. — When an insecti- 

 cide and a fungicide are to be used at the same time, it is 



