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ENEMIES AND THEIR LIMITATIONS. 
practical wisdom. People who do not know the eucalypts well enough to 
distinguish the species are very liable to conclude that, because one species is 
diseased, all are diseased or soon will be. Much that has been written on this 
subject within the last few years has consequently been very misleading. The 
truth is that our losses so far have been relatively small. Some of the most 
valuable of our species have been scarcely touched; others have suffered 
less or more severely; only one species, the familiar Eucalyptus globulus, 
has been seriously injured over extended areas. The first step towards 
effectual adjustment and remedy must be a study of the causes that have 
operated in aggravating the attacks of the enemy in these exceptional cases. 
The difference between the several species in liability to attack is due, of course, 
to difference in palatableness of their sap and tissues to the preying insects. This 
we cannot alter. All we can do is to observe and record results for guidance in 
our future planting, always remembering that insects as well as birds and mammals 
may gradually change their tastes and habits. The causes I propose now to 
discuss are those over which we may exercise control. 
We will consider first the case of Euc. globulus. The natural optimum of this 
species is on good lowland country in south-eastern Tasmania in about the latitude 
of Christchurch. There it formed a hundred years ago some of the noblest forests 
to be found in any country. It is one of a few species that have maintained 
approximate identity on both sides of the strait since Tasmania was ages ago rifted 
from the mainland. By the law of compensation between latitude and altitude E. 
globulus is a lowland tree in Tasmania and a mountain tree in Victoria. It is thus 
a cool country tree; and, as already intimated, it requires for its optimum good 
land and abundant moisture. In New Zealand we have planted this tree in a 
wide range of localities and usually without any regard to its requirements in 
respect to either climate or soil. We have planted it on warm lowlands where the 
winters are too mild; we have planted it on gravel beds and poor hillsides where 
the substratum is too dry. Thus wrongly planted, it may have flourished and 
grown rapidly for some years; but when the day of reckoning has come with insect 
enemies it has failed in resistance and died back. Where, on the other hand, it has 
been planted on deep subsoil, rich in alumina, well watered, and subject to cold 
winters, it has resisted or endured the attacks of its enemies and well maintained 
its vigour and beauty. In Canterbury and Otago the contrast between E. 
globulus wrongly planted and the same species rightly planted is very impressive, 
and may be noted by anybody travelling in those provinces. Insect allies will help 
this species everywhere, and all efforts should be made to encourage the scale¬ 
eating ladybird already introduced and to find the natural destroyer of the deadly 
gall chalcid; but our first and chief concern must be to give the species conditions 
of climate and soil similar to those of its native habitat in Tasmania. Where this 
cannot be done Euc. globulus should be cut right out and something else planted 
in its place. For all North Island lowlands there can be found species that will 
yield equally valuable timber and will prove far less palatable to either leaf eating 
or sap sucking insect enemies. h 
Another example showing how resistance to enemies depends upon vitality 
and vitality upon congenial conditions of soil and climate is found in the case of 
the almost equally familiar E. viminalis. Like E. globulus this tree requires for 
its best development good land, abundant moisture, and a cold winter. Near the 
