INJURIOUS INSECTS OF I909 AND IQIO. 145 
may persist in the seeds, on mummied fruit, or, in the case of shrubs 
and trees, in the twigs. Each fungus has its own life story: it gets 
into the habit of going through its life cycle in a definite and fairly 
constant way. It may require, during the course of its complete 
development, two different kinds of plants. For instance, the rust 
of Wealthy apples is caused by a fungus which lives in red cedars 
in the winter and on apple trees in the summer. It is necessary, 
then, in order to effectually prevent fungous diseases, to know the 
life habits of the fungi causing them. 
Preventive and curative measures are various. Spraying is re- 
sorted to when it is possible, by covering plant parts with some m1x- 
ture either to kill superficial fungi like powdery mildews, or to pre- 
vent the spores from germinating properly and thus infecting the 
plant. If the fungus gets inside the twigs or branches, pruning 
must be resorted to, while if it lives on decayed or dried fruit, 
leaves or rubbish, these should be removed and burned. Seed dis- 
infection is necessary in case the seeds are affected; such treatment 
is of value in preventing diseases like potato scab. Then, too, if 
the spores of the fungus persist in the soil, retaining their vitality 
for considerable periods, it is necessary to rotate crops or sterilize 
the soil. Again, it may be necessary, when a fungus requires two 
different plants for its complete development, to remove the so-called 
alternate host. Such a necessity often arises in dealing with apple 
rust; the removal of red cedars from the vicinity of the apple or- 
chard prevents the rust from living through the winter. Some 
fungi gain entrance to their hosts mainly through wounds; obvi- 
ously, in such cases, great care should be exercised in avoiding 
injuries, and in disinfecting and covering all wounds. Some varie- 
ties of fruit are more resistant to a certain disease than others; 
these should, naturally, be selected. Weather and soil conditions 
often affect to a remarkable degree the prevalence and severity of 
a disease; it is not always possible to control these factors, but some 
precautions can always be taken both in the greenhouse and in the 
field; the proper kind of soil can usually be selected, good ventila- 
tion can be provided for, and excessive shade can be avoided. 
Fungicides may be applied in different ways: they are usually 
used as steeps or sprays, sometimes as washes. The subject of 
sprays is still somewhat problematic. Bordeaux has been regarded 
as a “‘cure-all,’”’ but, under certain circumstances, it is objectionable. 
It stains the plant parts with which it comes in contact, so is un- 
fitted for use on ornamental plants or ripening fruit. Further, the 
