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Under hygiene are included cultural methods that aid the 
plant in resisting disease ; the establishment of crop rotations so 
that plants liable to the same diseases shall not follow each 
other in the same field; the prevention of contagion by the de- 
struction of diseased plants or parts of plants, and methods of 
pruning and training whether for removing diseased portions, as 
is often practiced with pear blight and plum black knot, or for 
regulating exposure to sun and rain as in some methods of train- 
ing grape vines. A good example of the effect of cultural 
methods in controlling a disease is furnished by the so-called 
“black rust’’ of cotton, which often causes serious losses on 
light sandy lands. Experiments have conclusively shown that 
this disease can be prevented by incorporating vegetable matter 
in the soil and applying potash fertilizers. This so increases the 
vigor of the plant that the facultative parasites causing the disease 
an unable to gain a foothold. On the other hand, the injury to 
pear trees from blight can be much lessened by preventing a too 
vigorous growth and securing the early ripening of the wood. 
This can best be secured by withholding cultivation and nitrog- 
enous manures, In this case the disease germs only flourish 
in the soft rapidly growing cambium and the hardening of the 
wood stops the spread of the disease. 
Topical app\cations may be made to the seed before planting, 
to the growing plant in the form of fungicidal sprays, or in some 
cases to the soil. Treatment of the seed is useful only in those 
cases where the source of contagion is from spores that adhere 
to-the seeds and are planted with them. Thus in harvesting and 
threshing oats the spores from smutted heads become dusted 
over the sound grains. It is almost or quite impossible to find 
seed for planting that is not more or less infested in this manner. 
If such seed is soaked in hot water of the right temperature orin 
certain fungicidal solutions, as formalin or copper sulphate, the 
smiut spores will be killed without injuring the vitality of the grain ; 
and the crop from this treated seed will be practically free from 
smut. Potato scah is a disease that is usually disseminated by 
the planting of diseased tubers for seed. Where once introduced 
in the soil it lives from year to year, so that seed treatment is not 
