256 FUNGICIDES AND GERMICIDES FOR PLANT DISEASES 



Formalin (forty per cent solution of formaldehyde gas in water). 

 A pungent, clear liquid, very irritating to eyes and nose. Ob- 

 tained at any drug store at about 40 cents per pint. Used for 

 potato-scab, oat smut, bunt in wheat, soil disinfection, etc. 



Lime. Offered for sale in the following forms, (a) Ground rock 

 or ground limestone ; air-slaked lime is of the same composition, 

 i.e. a carbonate of calcium. (6) Lump, barrel, stone, or quick lime ; 

 this is burned limestone, and should preferably test 90 per cent 

 oxide of calcium, (c) Prepared, ground, or hydrated lime ; this is 

 water or steam-slaked quicklime, dried and pulverized. Used as 

 an applicant to the soil to correct acidity (p. 77), for club-root of 

 cabbage, etc., and for preparing spray mixtures. 



Lime-sulfur (see page 294). In the many possible combinations, 

 lime-sulfur is coming to be equally as important as bordeaux mix- 

 ture, in the control of many plant diseases. 



(a) A mixture of equal parts of dry lime and powdered sulfur 

 is often dusted on plants for surface mildews. 



(b) A paste of equal parts of lime, sulfur, and water. This is 

 painted on the heating pipes in the greenhouse, and is valuable 

 for keeping off surface mildews. 



(1) Home-boiled dilute lime-sulfur. This solution has been 

 widely used in the past as a dormant spray, particularly for San 

 Jose* scale and peach leaf-curl. It is likely to be supplanted by 

 (2) or (3). For preparation see page 295. 



(2) Home-boiled concentrated lime-sulfur. When a great 

 deal of spraying is to be done, a concentrated lime-sulfur solution 

 may be boiled at home and stored in barrels to be used as needed. 

 For method of preparation see page 295. 



Test with a Beaume hydrometer, which has a scale reading from 

 25 to 35. Dilutions are reckoned from a standard solution 

 testing 32. If the solution tests only 28, it is not as strong 

 as standard, and cannot be diluted as much as a solution testing 

 32. The table on opposite page shows the proper dilution for 

 solutions testing 25 to 35 Beaume*. 



Decimals are given in all cases, but for practical purposes the 

 nearest even gallon or half gallon can be used, unless appliances for 

 more accurate measurement are at hand. It is understood in 

 making all dilutions that water is added to one gallon of the con- 



