HEART-ROT 123 
mycelium is incapable of growing in it. Thus a trench 
filled to the surface with lime might prove to be an effective 
barrier. But conidia and spore infection through the air 
is probably too common to make such a trench worth the 
labour of digging. Vigilance and forethought will help us 
much more than trenches. Heart-rot is a particularly 
insidious disease because its presence is not generally dis- 
covered till the trees are cut, so that not only have the 
trunks been getting more and more rotted, but they have 
been filling for many years a plot that might have been 
earning a useful rent. A skilled woodman can generally 
distinguish pumped trees by the hollow sound they emit 
when struck with the back of an axe or a stick, and by 
this time they are often ‘gouty’ at the base. But these 
means do not aid in the discovery of the disease till much 
damage has been done. Testing a tree with an increment 
borer, however, will disclose the presence of heart-rot as 
soon as the trunk is affected, and it is recommended that 
foresters should test their larch plantations from time to 
time with this instrument. It should be remembered that 
trees usually become pumped in groups, and if every tenth 
tree is bored every other year, an epidemic will be dis- 
covered before the loss or value becomes serious. Where 
one tree is found to be attacked, others in the immediate 
vicinity must be bored, and all the trees that are diseased 
should be cut out. They will only be wasting themselves 
and the land on which they are growing. Sometimes it 
may be necessary to clear fell, and in this case it is safer 
to grow a rotation of broad-leaved trees before replanting 
with larch or other conifer. 
Land which is being afforested for the first time presents 
a special case. Here pumping must be anticipated, and yet 
the exclusion of larch and spruce, and to a less extent 
Scots pine, would prove a serious obstacle in afforesting 
new land. Either the conifers may be grown in a mixture 
with hard woods and the former removed in the earlier 
thinnings, or, where it is thought advisable to plant pure 
coniferous. woods, the forester must watch them carefully 
