26 MASS. EXPERIMENT STATION BULLETIN 201. 



2. Sulfur Fungicides. 



The use of sulfur for disinfection of diseased plants was a common hor- 

 ticultural practice many years before the discovery of Bordeaux mixture. 

 The date of its origin has not been recorded. It was sometimes used alone 

 as a dust, and sometimes mixed with other substances such as lime. Thus 

 in 1833 William Kenrick (36) recommended a mixture of 1| pints of 

 sulfur, a piece of quicklime as large as the fist, and 2 gallons of boiling 

 water as a remedy for mildew of grapes. "Grison liquid,',' first prepared 

 by a Frenchman, Grison, in 1851, was considered at that time very effec- 

 tive, and is of historical interest as being a prototype of our modern lime- 

 sulfur solution. A mixture of flowers of sulfur, freshly slaked lime, and 

 water was boiled for ten minutes, and the supernatant liquid diluted and 

 applied with a sponge, especially for control of mildews (37). In these 

 early years, it should be noted, sulfur fungicides were never appUed for 

 protection, but as cures. The idea of protective spraying seems never to 

 have been considered previous to the cUscovery of Bordeaux mixture. 



(1) Lime-sulfur Solutions. 



The introduction of lime-suLfur into California from Australia for the 

 control of San Jose scale has been described elsewhere in this bulletin 

 (page 13) . Shortly after the peach growers of that State began using it 

 for the scale (about 1880), they noted that peach leaf curl, a fungous 

 disease, was also controlled by the dormant spray. It immediately began 

 to come into general use as a fungicide, first in the West, then in the East. 

 Its use as a protective spray for other plant diseases began about 1907, with 

 the observation by Cordley of Oregon (38) that when the dormant spray 

 for scale was apphed so late that the apple leaves had already unfolded, 

 the scab disease was also checked. Experiment stations in all parts of the 

 country began to investigate it, and within a few years it had almost sup- 

 planted Bordeaux as a spray for the apple orchard and for many other 

 crops. 



Formulas for Application. — Most of the commercial brands of lime- 

 sulfur test about 33° by the Baume hydrometer. As a summer spray for 

 the orchard, this should be diluted at the rate of 1^ gallons to the barrel. 

 If the home-made solution is used it should be tested with the hydrometer, 

 and the rate of dilution ascertained l^y consulting the dilution table on 

 page 15 of this bulletin. The dilution for dormant spray {e.g., for peach- 

 leaf curl) is the same as recommended for San Jose scale under insecticides 

 on page 15. 



Effect on the Fu7igus. — When lime-sulfur is exposed to the air on the 

 foliage, a process of oxidation begins (see page 14 for the equations repre- 

 senting this process) , which results in the liberation of sulfur in a very fine 

 state of division. It is the opinion of most investigators that it is this 

 nascent sulfur — not the sulfite, sulfate or thiosulfate of calcium — which 

 is of fungicidal value. The free sulfur is probably gradually oxidized 



