TREE INSECTS AND THEIR CONTROL 207 
twig will disclose the presence of the grub. 
Trees often become badly deformed as a 
result of this insect’s work. 
SAP-SUCKING INSECTS 
Oyster-shell Scale 
Habits This scale may be recog- 
and nized by its shape and appear- 
Damage. ance. In color it is brown or 
grayish, and in form it is long 
and curved, spreading at one end. It is 
easily moved by prying beneath it with 
a finger nail or knife-blade. The eggs are 
laid in the fall and remain all winter under 
the parent scale, encrusting the bark of a 
branch. Hatching takes place about the 
time apple-blossoms fall, and produces 
crawling insects which thrust their sharp 
beaks into the bark and feed on the sap for 
several weeks, until maturity and repeti¬ 
tion of egg-laying. Two broods a year are 
developed even as far north as New 
Jersey. 
Treatment. Nature provides for the 
destruction of a large per¬ 
centage of oyster-shell scales, through the 
agency of enemy insects. It is unsafe, 
however, to leave the work to these ene¬ 
mies, and spraying is necessary for com¬ 
plete elimination. The only time this 
spraying is effectual is immediately after 
hatching, shortly after the season at which 
apple-blossoms fall, when the lice-like 
insects are crawling, or have just inserted 
their beaks into the bark. Whenever 
these insects are visible they should be 
sprayed with miscible oils (lime sulphur 
hard on foliage), with kerosene emulsion, 
or with whale-oil soap in the proportion of 
one pound of soap to five gallons of water. 
Woolly Elm-bark Aphis 
Habits This insect causes more 
and damage to the looks of a tree 
Damage, than to its growth. Its 
attacks produce knotted and 
gnarled twigs and trunks on young trees. 
The American Elm is especially suscep¬ 
tible. An infested tree shows the rough 
knots, with clusters of white, woolly sub¬ 
stance and lice-like insects. These insects 
appear during the spring and summer, 
and spend their entire lives on a single 
tree. 
Remedies. The insect is easily con¬ 
trolled by spraying with 40 
per cent, nicotine sulphate, with kerosene 
emulsion or with a solution (5 to 7 per 
cent.) of one of the standard miscible oils. 
The spray should be applied thoroughly 
to the bark. If miscible oil is used the 
spray should be applied in the winter 
time; the other should be used as needed. 
European Elm Scale 
Habits While not often the direct 
and cause of a tree’s death, this 
Damage, sap-eating scale causes injur¬ 
ies which, by weakening the 
tree, lead to fatal attack by borers. The 
scale winters in crevices of the bark on 
the trunk and the larger limbs. At this 
period its color is brown, and it is embed¬ 
ded in a white substance resembling cot¬ 
ton. With the approach of warm weather 
eggs are deposited, and these hatch in 
early summer, producing insects resemb¬ 
ling lice. These insects have coloring of 
Remedies. Winter spraying is the 
most effectual means of 
destroying the scale. The spray should be 
kerosene emulsion, or a water solution of 
one of the standard miscible oils. Not so 
effectual, but useful when needed, is 
summer spraying with one of these pre¬ 
parations during the hatching season, in 
June or July. 
