Daily Kennebec journal., 1913-12-25


would be simpler and more effective than
need to be repeated each year of attack.
1t is a fact familiar TO students of
this family of insects that certain aphids
live for a few generations usually wing
iess) upon one food plant and then pro-
duce winged generation that migrates
to an entirely different species of plant
for the summer, where it establishes a
series of summer generations and by fall
produces a second migrant generation
that flies back to the original food plant
1t is here the true sexes occur and that
the winter egg is deposited,-stages abso-
lutely essential to the continuation of the
species.
Such a dual personality of certain
aphid species is condition which, be-
fore it is detected, betrays the economic
entomologist into many futile combative
attempts; but on the other hand the
same duality may reveal, when once dis
covered, the most vulnerable point of at
tack The work of the Maine Agricul-
tural Experiment Station along this. line
has resulted in discoveries of great
economic Importance.
The discovery that the aphid which
makes cone-shaped gals on black and
red spruce is the same species which lays
eggs on new growth white pine for pro-
geny that render the pine shoots weak
ened and unthrifty, gives the landscape
gardener his clue. If he treasures the
beauty of group Of white pines he
would do we'll to exclude red and black
spruces from the vicinity, or conversely
If he wishes to grow black spruces with
normal branches it is an indiscretion to
place them near white pines. bulletin
173). Again, when once it was ascer-
tanned that the woolly aphid of the alder
was masquerading on the maple leaves
in the spring under different name the
owner of ornamental cut leaved naples
had a heretofore unsuspected means of
protecting their foliage by the control
of the pest on its alternate food plant,
the alder which in many circumstances
is an easy point of control. bulletin
1850. Then more recently came the dis
covery that the wooly aphid of the ap-
pie is such a migratory species with two
distinct types of food plants; the elm, or
"original food plant on which the true
sexes occur in the fall and deposit the
overwintering egg, and on which 1t lives
in the deformed leaves in the spring; and
the apple to which it migrates from the
elm leaf and where 1t establishes itself
as a bark feeder during the summer
This species, in addition, produces in the
fall a generation that passes the winter
at the roots of the apple A circum
1l1 fty11rf In
that the apple alone was concerned In
the life cycle of this pest The elm-leai
curl which shelters the wolf in sheep S
clothing had previously been unsuspeeted
of other danger than that threatened the
elm itself, which except in the case OF
young trees is not usually great. But
the discovery of the annual migration OF
fresh infestation from the elm to the
apple and the knowledge that the elm
generations are an essential portion oi
the life cycle of the woolly aphid of the
apple puts a new significance upon the
economic status of the elm curl.
This surprising fact melted the Maine
Station Entomologist to concentrate at
tention during the past season chiefly
upon the woolly aphids of the elm ano
two bulletins just issued tNo. 2l7 and No
200 give the results of this important
investigation. AS a brief summary OF
the case it may be stated that we have
| in New England five, disunct thougf
closely allied species on the elm. Ol
these. the most important to us as ar
orchard state is the species previously
discussed which migrates to the apple
from the leaves of the American elm. A
second species common in the English
elm in Maine, and probably introduced
into this country with the tree, Is leai
curling aphid which migrates to the roots
of currant and gooseberry where it is 8
serious pest We do not yet know the
full cycle of the third species, which de
serts the curled leaf of the American
elm in the spring to pass It's summer II
some place still remaining to be discov'
cred The fourth species forms large
gall something the size and shape or fe
on the elm twig in the spring. but we
do not know its summer haunts. The
fifth species apparently confines itself tc
the elm alone where it is common, espec'
tally on young trees, in woolly clusters
on the bark.
1t is no slight task to follow through
the life cycle of migratory aphid, but
Judging from the marked success Of the
various projects undertaken by this Sta
ton. Maine, seems to be a favorable
field for work with this family of de-
structive insects, and other aphid prob
lens of similar nature are underway
which give promise of much economic
significance.
CHAS. D. WOODS,
Director.
Aniro Dac 1919