FUNGICIDES, PREPARATION AND APPLICATION 433 



In the dormant condition, where disinfection is necessary, 

 either copper or sulfur fungicides are safe and effective. 



As regards the physical form, fungicides are of two general 

 types, liquid and dry, or dust. Liquid fungicides have been 

 used almost entirely since the introduction of bordeaux mixture 

 about 1883. Several attempts to introduce copper fungicides 

 in dust form have failed. Recently, with the development 

 of sulfur fungicides, very successful and promising results 

 have been obtained in the application of dry, finely divided 

 sulfur. 



Insecticides may usually be safely mixed with fungicides. 

 Arsenate of lead is the insecticide now commonly employed. 

 It may be used with bordeaux, lime-sulfur, and in powdered 

 form with finely divided sulfur for dusting purposes. It may 

 not be safely combined with soda-sulfur compounds. 



Fungicides of all types are now generally manufactured, 

 although they may all be home-prepared. The standard 

 commercial brands are all about equally efficient and safe. 

 They are in general more expensive than home-made prepara- 

 tions, but at the same time they are usually more convenient, 

 especially where relatively small quantities are needed. 



Bordeaux mixture was from 1885 to about 1910 the chief 

 fungicide for fruit-diseases.. With the introduction of lime- 

 sulfur as a summer spray, bordeaux has taken second place. 

 It is by no means, however, entirely replaced by lime-sulfur, 

 and remains for American variety of grapes at least the only 

 safe and effective fungicide, while for all other fruits except 

 peaches, plums and apples (Fig. 126) it is just as safe and 

 effective as any sulfur spray. The active principle in bordeaux 

 is of course the copper. This is combined with the calcium 

 in the form of gelatinous colloid membranes suspended in 

 the water. The smaller the membranes, the better the mixture 

 stands up, and the more effectively it covers sprayed surfaces. 

 As the water evaporates from a sprayed surface, these minute 

 2r 



