246 INSECTICIDES, FrXGICIDES, AND WEED KILLEES. 



thus obtained by spraying every ten to twenty days, from 28 October 

 to 24 June, on winter wheat fields free from rust. Swingle found 

 that the proportion of plants attacked by rust is thus lowered from 

 84-2 to 18-3 per cent. It is useless to dwell u])on the failure of 

 bouillie bordelaise as a disinfectant of corn-seed againsi lust germs; 

 not only does it have no effect, but it is quite useless in treating a 

 fungus, the method of evolution of wbich is so dit^'ei-ent from that of 

 the black rust, and which has methods of propagation which can only 

 diminish the effect of disinfection. 



Puccinia Priini, Pers. (rust of stone-fruit trees). — Pierce success- 

 fully treated this fungus by three sprayings with bouillie bordelaise 

 at a month's interval. The spraying was begun before flowering. 

 Trees so treated preserve their green leaves. 



Puccinia compositarimi, Schlechtend (mildew of the compositai). — 

 It is successfully treated with bouillie bordelaise. 



Puccinia Tanaceti, D. C, — Successfully treated by Halsted. 



Puccinia Bibis, Aecidium Gros^idarice (mildew of the gooseberry). — 

 Sorauer recommends preventive treatment by bouillie bordelaise. 

 Eriksson recommends removing the diseased leaves in the autumn, 

 and to spray soil and plant copiously in the spring. 



Uromyces Betas, Kuhn (beet mildew). — Nijpels relates that three 

 sprayings with bouillie bordelaise at a month's interval, commencing in 

 June, appreciably diminished this disease. 



Gynosporangium Sahina, Wint. (mildew of the juniper), and 

 Boestelia cancellata, Eebent (pear leaf cluster cups). — Knowing the 

 polvmorphism of this uredinae it has been recommended to overcome 

 this disease by destroying all the juniper-trees on which the fungus 

 exists in its telento and uredo forms, so as to prevent the evolution of 

 the fungus. It is sometimes made to disappear in that way, but very 

 often the disease appears on the pear-tree, when there are no junipers 

 in the district. It is then necessary to resort to spraying with bouillie 

 bordelaise. The experiments of Weiss and Delacroix have shown that 

 this process is evidently, if not absolutely, efficient. The first spraying 

 ought to be made before the unfolding of the leaf, the second before 

 flowering, and the third at a month's interval. 



Peridermium Pini, Wall, (vesicular rust of pine bark). — In 

 addition to the destruction of swallowort and groundsel, preventive 

 sprayings with bouillie bordelaise in May have given such good results 

 that this method has been adopted by the Belgian Forestry Depart- 

 ment to prevent this disease in pine plantations. 



Exoascus deformans, Fuckel. — It has been supjn-essed by the use 

 of bouillie bordelaise. Benton, Taft, Selby, Duggar, Derschau, Murill, 

 and others, have examined the action of copper compounds on the 

 leaf curl and described the good effects got by rational ap])lication of 

 bouillie bordelaise. It follows from their experiments that the bouillie 

 bordelaise is the more active the sooner it is applied. The first spray- 

 ing should be done before flowering in March and April, when the buds 

 begin to swell. At that time strong bouillie made with 3 per cent of 

 blue vitriol may be used ; however, 1 per cent bouillie would sufl&ce 

 (Murill). The second spraying is done after the fall of the flowers, with 



