204 
TREES AS GOOD CITIZENS 
Cankerworm 
Habits This is the worm commonly 
and known as the “measuring 
Damage, worm” or “looper,” because 
of its curious way of looping its 
body in crawling. An attack by this 
species may result in the destruction of 
the entire foliage of a tree. The species is 
divided into spring and fall types; the 
latter is the one which attacks shade trees. 
The eggs of the fall moth, shaped like 
flowerpots, are laid in regular rows, 
usually in rings around twigs near the 
end of a branch. The eggs hatch into 
caterpillars when the leaves start to 
expand in the spring. These cater¬ 
pillars feed on the leaves, and in June spin 
silken threads by which they descend to 
the ground to bury themselves beneath 
the surface. They emerge late in the fall. 
The egg-layers have no wings and must 
crawl up the trunk of a tree to deposit 
their eggs. 
White-marked 
Habits One of the worst insect ene- 
and mies to the Elm and other 
Damage, shade trees, sometimes destroy¬ 
ing the foliage of the trees in 
an entire community. City trees seem 
especially susceptible to its attacks. 
When a tree becomes infested the signs 
are at once visible, in the form of conspic¬ 
uous egg masses on the trunk or larger 
limbs; these masses are present from the 
time of the egg-laying in September, until 
the following spring. They are shiny 
white, frothy looking patches, with four or 
five hundred eggs in a single cluster. 
Hatching takes place in May, with a 
second brood in August, and each cluster 
may produce hundreds of caterpillars. 
The caterpillars immediately attack the 
leaves, first reducing them to transparent 
skeletons and finally devouring all but the 
principal veins. After five weeks the 
caterpillars weave cocoons in which they 
go through the stages of transformation, 
emerging as moths to repeat the egg- 
laying and hatching process for a second 
time and in warm climates for a third time 
during the same season. The full grown 
Remedies. If unchecked by their 
natural enemies the can- 
kerworms become a serious menace to 
trees. The first step is to prevent the 
wingless females from crawling up the 
trunks in order to lay eggs. This may be 
done by banding the trees with some 
sticky substance or cotton batting. 
(Page 192.) These bands should be placed 
late in September and kept in position 
until the end of May. Where banding 
has not been done, or where it has not 
proved effectual, a tree which shows 
signs of being heavily infested should be 
promptly sprayed with arsenate of lead. 
Necessity for spraying is shown by the 
appearance of perforations in the leaves 
when they are opening in early spring. 
Tussock Moth 
Remedies. Destruction of the egg 
masses in the fall or winter 
is the simplest and most effectual means 
of control. They may be easily picked 
off by hand, or scraped off and burned; or 
they may be destroyed by spraying or 
daubing with creosote oil, kept liquid by 
being mixed with turpentine. It will be 
found that because the masses are loosely 
attached the removal can be accomplished 
with little effort. If any of the eggs 
remain and are hatched the tree must be 
thoroughly sprayed with arsenate of lead, 
completely covering all infested foliage. 
The spraying should be done with equip¬ 
ment and method similar to those out¬ 
lined for the control of the fall web worm. 
(Page 203). 
The tussock moth does not appear 
every year, for the reason that it has a 
number of natural enemies which keep 
it in check. 
