INSECT PESTS 
OF ORNAMENTAL PLANTS 
E. P. FELT 
New York State Entomologist 
Differing Slightly, Greatly, or Sometimes Not At All, from the Well-known and 
Common Pests, the Different Principle of Attack on These Sets Them Quite Apart 
HERE are two striking facts connected with the war 
on pests in the ornamental garden which distinguish 
it from the similar war carried on in the field and 
orchard. These are, first, that it is frequently advisa- 
ble and necessary to spend much more than the intrinsic value 
of the plants in order to accomplish the desired result of pro- 
tecting them from injury and disease; and second, that the 
grower of ornamental material is hampered by being obliged to 
deal with insects which, owing to their commercially relative 
unimportance, have been given comparatively little study. 
The gardener has no difficulty in handling the more common 
pests since these have come, through experience, to be almost as 
well known to him as many of the enemies of the vegetable 
garden. The appearance, for example, of almost any leaf 
feeder — unless in unusual numbers — warrants the deduction 
that it can be controlled by spraying with a poison, which is 
usually supplied by arsenate of lead. And unless the plant is 
an abnormally tender species about three pounds of the paste 
to fifty gallons of water are generally used. Everyone knows 
moreover that the one essential is that this poison be placed 
where the insect is obliged to eat; otherwise comparatively 
poor results will follow. 
This general rule does not apply to hordes of resistant leaf 
feeders, however, such as rose beetles, which sometimes appear 
in swarms and, before they obtain a killing dose, may seriously 
injure foliage that is fairly well covered with poison. Special 
methods may be necessary in such cases, such as netting the 
plants, if these are specimen trees or shrubs important to keep 
in a satisfactory condition. 
T HE soft-bodied sucking insects, especially plant lice, are 
easily controlled with a contact insecticide — notably nic- 
otine-sulphate and soap, applied at the strength generally 
advised — provided the spray is actually thrown upon the 
insects. (Recent developments indicate that this preparation 
remains upon the foliage, and retains its deadly properties for 
certain insects, for four or five days). And most plant lice are 
very susceptible to this treatment; but a marked exception 
exists in some of the woolly aphids, such as the Alder blight. 
Even here, however, fairly satisfactory results may be secured 
if a forcible spray is used and the insecticide, by this force, be 
driven through the protective woolly covering and thus brought 
into positive contact with the insect itself. Another difficult 
group are the gall-inhabiting aphids, such as those of the Spruce- 
cone gall. These can be successfully controlled if the spraying 
is done while the insects are exposed to the treatment, which of 
course they are not if protected by the plant tissue of the gall. 
There are other more resistant sucking insects — the scale 
insects especially — which are not so readily controlled. In 
order successfully to combat these pests some knowledge of their 
life history is necessary. The San Jose scale, oyster-shell scale 
and scurfy bark lice can be checked by winter spraying with a 
lime-sulphur wash; or the latter two, hibernating in the egg 
stage, may be controlled by delaying the work until the crawl- 
ing young appear, in May or early June, and then spraying with 
a moderately strong insecticide. 
B ORERS and the general procedure therefor are well under- 
stood, and the early signs of their presence — the “saw- 
dust” castings — are easily recognized. It is then simply a 
question of being able to destroy the enemy in its burrow 
without inflicting undue injury upon the plant; or else of 
removing and burning the infested portions. The course to 
be adopted must be determined by conditions. In some in- 
stances, especially with the larger trees and more valuable 
shrubs, it may be practical to destroy the borer by injecting 
carbon bisulphide into the burrow and sealing the orifice with 
soap, putty, or even clay. 
The advantage of this treatment is that little or no cutting is 
necessary, and in many instances even the infested branches or 
portions of the tree or shrub can be preserved. But there are 
other cases where the infestation is of such character as to make 
it impossible to destroy the insect without burning the infested 
portions. The gardener should be able to recognize these limi- 
tations, and should never hesitate about cutting and burning 
when conditions demand heroic treatment. This is particu- 
larly necessary if there be invasion by bark beetles — on Pines 
for example — or Ambrosia beetle, as in the case of the pitted 
Ambrosia beetle sometimes injurious to Rhododendrons. 
PREPARED INSECTICIDES AVAILABLE 
T HERE are many commercial preparations of all the in- 
secticides needed on the market, in various sized containers, 
and those offered under brand or trade names are suitable 
combinations of the essentials. Each ’differs somewhat in the 
proportions of essential ingredients, and close adherence to the 
manufacturer’s directions for each particular kind is essential. 
Since the task of properly proportioning and mixing the ingre- 
dients is a considerable one, and messy into the bargain, it is 
usually preferable to avail oneself of the ready-mixed prepara- 
tions, especially as these have now been standardized and may 
be relied upon as efficient. 
T HE following are brief accounts of a number of relatively 
little known insects which have been brought to notice 
during recent years: 
IN THE FLOWER GARDEN 
Iris beds are occasionally badly injured by whitish boring 
caterpillars, some two inches long when full grown. This 
pest attacks the stems, causing wilting, and gradually works 
downward into the roots. The eggs are laid in the fall and 
practical experience has shown that winter burning of the debris 
on Iris beds, where this can be done without injuring the roots, 
is the simplest and most effective method of controlling the pest. 
The removal of injured stalks and their destruction, together 
with the contained caterpillar, hastens the accomplishment of 
this end. 
Iris roots and certain bulbs such as those of Amaryllis and 
Onions, may be attacked by dirty, grayish-yellow maggots, 
nearly half an inch long when full grown. These are the young 
of the Lunate onion-fly, an introduced species recorded as 
quite destructive to Onions in Europe, though in this country 
its injuries appear to be very limited. It is very probable that 
attack is favored by the work of the iris borer. Good cultural 
methods are at present the best preventives that can be advised. 
Nasturtiums (Tropaeolum) are occasionally rather badly in- 
fested with aphids or plant lice. Spraying with a nicotine-soap 
preparation before the insects become excessively abundant 
is the best remedy that can be devised. 
