II 
Some Bacteriae Diseases oe Plants. 
quantities of commercial fertilizers containing a great deal of 
nitrogenous material and heavy pruning all tend toward the growth 
of tender, succulent shoots. It is in this sort of plant tissues, 
gorged with sap, that the blight germs can grow and multiply most 
rapidly. Biting insects whose mouth parts are contaminated with 
the causal microbes, are most partial to these juicy shoots and leaves, 
and their bites often serve to infect the tree. 
It is evident, then, that vigorous, healthy, rapidly growing, too 
well cared for orchards are more liable to the disease than others, 
and since these are factors which the grower can control, it is he 
who must strike the happy medium which will not permit the trees 
to suffer and yet will not give ideal conditions for the development 
of the germs. 
Prevention and Treatment. —The treatment of fire blight 
is of two kinds—the one, preventative, which aims at making the 
tree resistant to the attacks of the disease; the other, curative, which 
is intended to exterminate the harmful microbes and thus prevent 
their spread. 
I. It is obvious, if we are to render our trees resistant to 
blight, we must avoid those conditions which increase the predis¬ 
position to the disease. We have already mentioned the most potent 
factors in the propagation of blight as high cultivation, rich 
manures, commercial fertilizer high in nitrogenous material, exces¬ 
sive soil moisture, and high pruning. In short, anything which fa¬ 
vors the rapid growth of tender, succulent shoots should not be 
practiced. It is understood, of course, that these suggestions are 
not to be followed without reason, or the trees will suffer from 
troubles other than the blight. The trees should be allowed to ripen 
their wood, and to this end the grower must use some means which 
will limit the moisture in the soil. It is recommended that some 
good cover crop, such as oats, be used for this purpose in localities 
where the necessary moisture is supplied by rain and where the 
growing period is apt to be prolonged into the late summer because 
of excessive soil moisture. 
In irrigated regions, where the water is entirely under the 
control of the grower, the problem of ripening the wood and pre¬ 
venting late succulent growth is a comparatively simple one. Good 
results have been obtained in eradicating blight from afflicted or¬ 
chards by withholding water altogether for long periods and also 
by limiting the amount supplied to the minimum necessary to keep 
the trees alive. 
Prof. Paddock* gives the following account of an orchard suf¬ 
fering with pear blight, which had not received any water for two 
♦Unpublished Notes 
