REFLECTIONS ON DISEASE TREATMENT 177 
important, so that spraying may be conducted at the 
right time. | 
The method of applying the spray is a matter of 
considerable importance, for no matter how destructive 
to the disease organisms the liquid may be, or how 
perfectly it may wet the surface, it is of no avail if not 
directed in the proper direction or with the required 
force from suitable machines. 
It must also be remembered, however, that under 
certain conditions the cure may be worse than the 
disease, and consequently the effect of the spray upon 
the health and growth of the plant must be taken into. 
consideration in choosing a spray liquid. In this respect 
physical conditions of the environment at the time of 
spraying and for some days afterwards are important. 
Thus a spray which is perfectly harmless to the plant 
under cool, moist conditions may scorch it beyond remedy 
when the air is hot and dry. 
Fungicides 
A fungicide is a chemical compound which is poisonous 
to fungi and which, when correctly applied to the surface 
of the living plant, serves to protect it from attack by 
fungus parasites. A good fungicide should be extremely 
poisonous to the pathogen against which it is directed, 
but harmless to the plant to which it is applied; it 
should completely wet the plant surface and adhere 
strongly once it is applied; and finally it should be 
cheap and easy to use. 
The discovery of Bordeaux Mixture by the Frenchman 
Millardet in 1883 may be said to mark the commencement 
of fungicidal treatments. Since that time scientific 
investigations have produced a large number of prepara- 
tions of proved fungicidal value. 
Bordeaux Mixture 
The discovery of the fungicidal value of Bordeaux 
