366 [ AssEMBLY 
ficient delicacy would be exposed to permit infection. Observation 
has shown that there issome connection between the attacks of blight 
and the direction of the wind, for it has been noticed that the trees 
on the windward side of an orchard are sometimes first and most 
severely blighted, and again, that a tall hedge has checked the march 
of the disease ; all of which is quite reconcilable with the view pro- 
osed. 
Another possible mode of contagion is by the punctures of insects. 
Having come in contact with the fresh exudation of the blight, they 
would certainly carry some away, to be distributed at the places 
where they alight But I am not inclined to consider this a very 
frequent means of contagion. 
It is apparent that the disease does not find access to the plant by 
way of the roots, both from my experiment and from its local 
nature.* 
What vow shall be the nature of the controlling treatment? 
None can be suggested that promises so well as the old one of the 
knife — vigilantly destroying every trace of the disease. ‘The most 
satisfactory course would be to remove each limb as soon as the 
bark becomes discolored, but this is impracticable on account of the 
inconspicuousness of the change. ‘The blackened leaves will usually 
be the first indication of its presence; the disease will then have 
been in progress two or three weeks or more. The limb is to be re- 
moved some inches below the point.where the bark is discolored, the 
distance being greater where the disease is of longer standing. Un- 
less the knife has been carelessly passed thfotigh a diseased part, . 
there is noneed of using disinfectants, and in that case it is easier to 
take another knife than to cleanse the contaminated one. By regu- 
larly inspecting the orchard once a fortnight or so, the disease, ex- 
cept in very severe attacks, may be kept entirely in check with only 
now and then the loss of a tree where it has found access to the 
trunk. Whether any harm can arise from the limbs being left upon 
the ground cannot be definitely stated, but there is probability of it, 
and it is certainly a surer course to annihilate all life in them by ° 
burning. 
It may be well to say a few words about proposed remedies that 
are not likely to be of value. The most promising of these is check- 
ing the growth of the tree by mulching, withholding of fertilizers 
and cultivation, or putting the land into grass. That this will! sne- 
ceed in giving a certain immunity cannot be questioned, but whether 
the gain is greater than the loss is to be doubted. The method ~ 
might, however, be serviceable during periods of unusual severity, 
lasting generally from three to five years. The application to the 
soil.of sulphur, salt, potash, lime, fertilizers of all sorts, drugs, poi- 
sons, or any thing whatever, is not likely to afford any relief or im- 
* It is doubtless a slip of the pen when Penhallow says that pear blight ‘‘in- 
volves the entire system,” as in the case of peach yellows.—Popular Science 
Monthly, XXV, p. 388. 
