Oxford Democrat. [volume] (Paris, Me.) 1833-1933, 1920-09-28
The Birch Trees.

Inc blrcn Trees.
"What is the matter with tn,
birchesP" Is the question that is coming
in from all sides to the Maine Agricul
tural Experiment Station.
The matter Is Bucculatrix canadensi
sells which sounds long enough to bt
serious. The owner of this name il
(when full grown) only about one-fourtt
of an inch long which might lead us to
believe that the threat he is putting uI
against the birches is backed up by hii
numbers rather than by his size. One
yellowish green caterpillar quarter of an
inch long can't eat off the green tissue
Of very many leaves and the fact, there.
fore, that birch trees over at least one
third of the state have at present the
appearance of having been scorched
brown tells its own story as to the abun-
dance of the pest this season.
What 10 to be done about It is q ques-
tion quickly answered. Nothing, this
fall, except to charge our minds with
the feasibility of spraying ornamental
birches with arsenate of lead early next
August.
The reason for postponing treatment
until the next generation begins its
career of destruction is found in the
circumstance that this present genera
tion has already done its worst and be-
ing, therefore, about through with its
eating, any effort to tempt its appetite
with diet of srenic would be unavail.
ing.
How much damage the insect has
done on trees is question not 80 easily
disposed OF. II, as previous attacks
have given Us reason to think, the work
of these late csterpillars means "merely''
the killing off of the birch leaves at q
time when they have already served
their purpose and are about ready to die
the more gradual, normal, fall death
anyway, the damage would not appear
to be severe tax on the strength of the
tree.
If, however, as observations in certain
localities this year might seem to indi-
cate, the birches have been stimulated
to push the leaf buds, which should
over winter, into an abnormal state of
development in an attempt to replace
the dying leaves with the foliage that
should belong to next spring, the
chances of winter injury to trees seem
fairly certain.
The habits of the culprit are peculiar
and interesting. When the tiny cater.
pillar Is ready to molt (as all caterpillars
must several times in the course of their
growtb) 1t spins circular mat of white
silk on the leaf or twig beneath which it
rests undisturbed while it discards its
tight coat of skin. These molting mats
look specifically like whitish scale In
scots aud on that account sometimes
cause people to think their trees are in
tested with coccids (scale insects) in.
stead of caterpillars.
When the larva is several weeks old
and has made several of these moltiDg
mats leach q size larger than the pre-
vious one) he becomes "full fed" and
spins the true cocoon. This is an oval
yellowish case with fiat base and with
five or six sharp longitudinal ridges.
This type of structure Is spoken Of as a
"ribbed cocoop." Within 1t the insect
undergoes the changes incident to the
pupal transformation and the next sea-
son the insect which wove the cocoon
about a caterpillar emerges as moth
ready to deposit eggs for the next gener-
alton. Some of the cocoons are attached
to the twigs and trunk of the tree but
greater numbers are spun in rubbish on
or near the ground.
This insect was very abundant In
Maine in 1909 and has been conspicuous
| on two occasions since then. On ac'
count of it's frequent appearance owners
of ornamental birches would do we'll to
watch the first signs of its coming and
spray with arsenicals early in August
any season when it is found to be pres
ent.-Chss. D. Woods, Director.