148 Control of Parasites 
fed, the main remedy is not to allow trees to get into such 
vulnerable condition. If a slight infection is noticed in 
time, in addition to promoting the general vigor of the 
tree, an application of whitewash with Paris Green added, 
or of strong whale-oil soap suds with a little crude carbolic 
acid added, repeated as needful, may be employed. It may 
also be possible to cut out small infested areas of wood, and 
treat them antiseptically like other wounds. This has been 
successfully done on old elms at Brussels. 
In the forestry practice of Europe, baiting of bark-beetles, 
which are specially destructive to spruce forests, is the only 
practical remedy besides clean lumbering. The beetles 
thrive most readily under the bark of the freshly felled timber, 
and, therefore, barking the trees immediately after felling, 
and the removal or burning of rubbish is practised. In 
addition, in the spring, a few “trap trees” are felled or 
billets laid out in the endangered places, on which the beetles 
assemble in large numbers to lay their eggs; the trap trees 
can then be removed and burned. 
If the pest is once established, nothing can be done, except 
to cut out the infested trees in order to avoid further spread. 
Root Destroyers. The root pests—such as the cut-worms, 
larve of certain moths; the wire-worms, larve of the well- 
known clicking-beetles; root-lice, like the celebrated Phyl- 
loxera, which made such havoc among the vineyards of 
France, and other plant-lice, which feed on roots either 
wholly or at some time in their development — these are 
more to be feared for the lawn grass and other tender plants 
and for young tree seedlings, than for older trees, although 
they occasionally injure these too. ‘Those which spend 
one phase in the open (and then they are also sometimes 
feeding on foliage, as the clicking-beetles and lice) may be 
decimated by poison or by collecting during that phase. 
