52 
House & Garden 
HARSH TREATMENT FOR TREE PESTS 
How the Destructive hisects may be Recognized and the Various 
Methods by which They may be Destroyed 
E. P. FELT 
T he last fifty years or thereabouts have 
witnessed the introduction of a num¬ 
ber of destructive tree pests, such as the elm 
leaf beetle, the gypsy motli and the leopard 
moth; while native insects, like the white 
marked tussock moth, the bagworm and 
the sugar maple borer have not been slow 
to take advantage of extensive and reliable 
food supplies and a considerable degree of 
protection from bird life. These recent de¬ 
velopments have resulted in a gradual in¬ 
crease in insect depredations which for the 
most part have been regarded as of little 
consequence, or considered as inevitable, 
and a careful examination of our trees at 
the present time shows the effect in a 
lamentable scarcity of perfect specimens, 
many of them with appreciable injury and 
not a few seriously deformed as a result of 
insect work. The operations of the sugar 
maple borer are particularly insidious, 
since a period of five to ten years may 
elapse between an apparently insignificant 
injury and the death of a considerable pro¬ 
portion of a symmetrical maple in its prime. 
T he long period between planting and 
the attainment of maturity makes trees 
particularly susceptible to insect attack. It 
requires a generation to produce even a 
moderate sized tree, while the stately mon- 
archs on lawns and in parks may have 
complacently viewed the passage of five or 
six human generations. Tree hazards are 
immensely greater than they were fifty 
years ago and we who have benefited by 
the foresight of our predecessors should 
recognize this and take precautions which 
will make it possible to hand down an un¬ 
impaired inheritance. This can be done 
only by recognizing the dangers and antic¬ 
ipating injury, rather than waiting until 
it is necessary to reshape badly deformed 
trees or reinvigorate those which have been 
devitalized. 
llie acceptance of insect ravages as in¬ 
evitable is an inheritance from an age 
which knew little or nothing of arsenical 
poisons, and had no knowledge of a spray¬ 
ing apparatus better than a whisk broom or 
a hand pump originally designed for the 
washing of windows. Generally speaking, 
insect depredations may be prevented, and 
this is particularly true of the more valu¬ 
able trees on lawns and in parks, and to 
a less degree in the case of woodland areas, 
though much can be accomplished in bet¬ 
tering the forest situation by modifying 
the conditions which affect the abundance 
of insects, and particularly by protecting 
certain of the more efficient insect enemies, 
the birds. 
Our favorite shade trees are the Ameri¬ 
can elm and the sugar maple, though 
horse-chestnuts, European elms, Norway 
and soft maples are strong competitors; 
the last named and the Carolina poplar 
being somewhat generally planted in certain 
localities on account of their rapid growth. 
These latter are cases where permanency is 
sacrificed for early effect, and in the case of 
the Carolina poplar at least it would 
usually be advisable to make provision for 
the future by the judicious interplanting 
of more permanent trees. 
All of these trees and others, which are 
occasionally planted on streets, lawns or 
in parks, have their insect enemies, certain 
of which are serious. Some of the more 
important of these pests are briefly dis¬ 
cussed below in the hopes that it may re¬ 
sult in the better protection of the trees and 
a fuller realization of possibilities in the 
growing of these beautiful and inspiring 
natural ornamentals. 
The American elm is an exceedingly 
valuable shade tree in spite of its being sul)- 
ject to attack by a number of destructive 
insects, such as the elm borer, the leopard 
moth, the European elm bark louse, the 
elm leaf beetle, the white marked tussock 
moth, canker worms and various scale in¬ 
sects. This constitutes a rather formidable 
array of enemies, yet elms are still very 
prevalent in the country, though in some 
areas they have suffered grievously, and in 
not a few instances magnificent trees have 
been hopelessly and usually needlessly de¬ 
formed, simply because they were not 
given a reasonable degree of protection. 
A weakened tree should always be 
carefully examined to learn the cause 
of the trouble, and if this is irremediable 
it is frequently better to remove the tree 
rather than allow it to persist for years in 
an unfavorable condition and be a possible 
source of danger to trees nearby. Some¬ 
times this condition results from poor 
drainage, drought, winter injury, loss of 
important roots, injury by gas, etc. The 
development of weaknesses may easily 
afford conditions favorable to insect attack 
and result in a series of depredations which 
may not only destroy the one tree but 
spread to others with disastrous results. 
The weakened or dead limbs in the top 
of a tree, or on one side, may be due to 
the work of borers, and in such cases the 
early cutting of the affected portions and 
the treatment of the cut surfaces with a 
protective material, such as a good water¬ 
proof paint or tar, is by all means advis¬ 
able. The early work of the leopard moth 
is limited mostly to the smaller limbs or 
branches, and consequently systematic 
cutting and burning of the infested 
branches Mdll do much to check the pest. 
The destructive leaf feeders occurring so 
commonly upon the elm, namely the elm 
leaf beetle, the gorgeously colored, dark 
tufted caterpillars of the tussock moth and 
the dark looping canker worms are all 
readily controlled by early and thorough 
spraying with a poison, such as arsenate 
of lead, using three pounds of the paste to 
fifty gallons of water, and in the case of 
the elm leaf beetle take particular pains to 
apply it to the underside of the leaves if 
the work is done sometime in June, because 
the grubs feed only on the lower surface of 
the foliage. Timely applications will pro¬ 
tect trees from this insect even if those 
nearby are badly injured. 
O ccasionally small branches of 
American elms die because of a rather 
thick incrustation with a brownish, oyster 
shell-shaped scale about 1/10" long. This 
insect and the related scurfy scale, the latter 
easil)^ recognized by its whitish color, are 
sometimes rather injurious. In the winter 
they are very minute, white and reddish eggs 
respectively, the young appearing the latter 
part of May or early in June. Both can 
be checked by early spring applications 
with a miscible oil, 1 to 15, or with a 
tobacco soap combination when the tender 
young are crawling. 
The European elms, especially the 
Scotch elm, are occasionally seriously in¬ 
jured by the elm case bearer, a small cater¬ 
pillar w'hich lives in a somewhat flattened, 
cigar-shaped case about three-eighths of an 
inch long, eats a hole through the epider¬ 
mis of the leaf and devours all of the more 
tender inner tissues in a somewhat char¬ 
acteristic angular excavation, the maximum 
dimensions of wdiich are limited by the 
length of the miner’s body. Badly infested 
leaves have a peculiar spotted appearance. 
A closer examination would disclose a 
small hole about the size of a pin head near 
the center of each spot. Early spraying 
wdth arsenate of lead, three pounds of the 
paste to fifty gallons of water, is effective. 
The European elms are very susceptible 
to injury by the somewhat recently intro¬ 
duced elm bark louse; an oval, brownish 
insect about 1/10" long, w'hich w-inters up¬ 
on the twigs in a partly grown condition 
and may be easily killed by oil applica¬ 
tions as described above. This insect oc¬ 
casionally becomes so extremely abundant 
that portions of twigs and leaf stalks are 
yellowish with the numerous young in early 
Tuly and the walks under infested trees 
kept moist with honeydew during the hot, 
dry weather of mid-summer. 
The foliage of European elms is some¬ 
times greatly disfigured by the irregular 
(Continued on page 82) 
