Daily Kennebec journal. [microfilm reel] (Augusta, Me.) 1870-1975, 1912-07-17
Woody Aphid of Apple.

| i or more tlan 100 years the WoolN
laphid has had world wide recognition
las one of the most serious insect ene-
Imies of young apple trees. Statistics
for 1911 on year old nursery stock
based on observations made at three
nurseries containing respectively about
10000; $4,000; and 100000 trees, show
led that from 20 per cent To % percent
of the trees were infested by the woody
laphid. AS from 20 to 40 million of
American grown apple seedlings are
fused in this country every year, the
Significance of so high percent of in
festation is at once apparent.
1t is, therefore. with no slight inter
est that the entomologists of the Maine
Agricultural Experiment Station have
| been seeking to ascertain a previously
unknown point in the life cycle of this
pest, and have made the discovery that
this cycle includes three generations
which are passed in what is known as
| the elm leaf curl" The dis
figured and eurled leaves of the
elm in the spring are everywhere
as familiar as the woody masses on the
apple bark, but the elm generations
have not previously been known to
/ nave dtiN COllit6C0lOH WIFI the dDDie
pest and it has all along borne a dis
| tinct name.
1t is fact familiar to students of
this family of insects that certain
aphids live for few generations (us-
ually wingless) upon one food plant
| and then produce a winged generation
| that migrates to an entirely different
species of plant for the summer, where
| it establishes a series of summer gem
erations and by fall produces second
migrant generation that flies back to
the original food plant. 1t is here the
| true sexes occur and that the winter
jegg is deposited,-stage absolutely es-
sential to the continuation of the spe-
cies.
The woody aphid of the apple is such
a migratory species with two distinct
types OF food plants elm. or or
iginal food plant" on which the trne
sexes occur in the fall and deposit the
loverwintering egg, and on which il
lives in the curled leaves In the spring:
and the apple to which it migrates
from the elm leaf-curl and where il
establishes itself as bark feeder dur
ing the summer This species. in adj
NANACilf PiOuutSS III the TAIL d genera
ton that passes the winter at the
roots of the apple. circumstance
which has led to the assumption that
the apple alone was concerned in the
life cycle of this pest, and the elm-lear
curl which shelters the wolf in sleeps
clothing has been previously unsus-
pected of other danger than that
threatened the elm itself which except
in the case of young trees is not usual
ly great. But the discovery of the an
nual migration of a fresh infestation
from the elm to the apple and the
knowledge that the elm generations are
an essential portion of the life cycle
of the woody aphid of the apple and
that this species cannot continue with
out access to Tie elm, put new sig
nificance upon the economic status of
the elm leaf curl
A few seasons ago while the ento-
biological department of the Maine As-
ricultural Experiment Station was at
work with the gall aphids of the elm
(Bul. 1919 clue was found which led
to the suspicion that the aphid of the
elm leaf curl was not a distinct species
but really the woody aphid of the apple
in very successful disguise. Field OBJ
servations were made during two sea-
sons with this problem in mind but
with both food plants under out of
door conditions, not possible to con-
troll the case was found too involved
and difficult to settle in this way. This
past winter, however, material under
control conditions was secured by rails
ing Seeding apples in the greenhouse
where infestation from the woody aphid
was rendered impossible. Elm leaf curl
with the migrant generation was Sc
cured from the south about twp
months before the same state would
be available in Maine and migration
tests were made. The winged forms
from the elm were Gagged over Seeding
apples and their progeny, growing
along creases in the bark and exposed
roots of the apple seedlings. covered by
typical white waxy filaments, are un-
mistakably the woody aphid of the APP
pie, established in thriving colony of
successive generations, maturing and
producing young as is normal for the
summer generations on apple bark.
new light is thus thrown upon the
whole economic aspect of the problem
by this discovery that the migrants
from the elm leaf curl can establish
colonies of woody aphids upon apple;
and that the presence of the elm is
necessary to the perpetuity of the
species. The protection of seeding
apples from infestation by the woody
aphide while still in the nursery has
heretofore been an exceedingly diff
cult matter But with the knowledge
that the source of danger lies in the
migrants from the previously unsus-
pected elm curl, it is possible to con-
troll the nursery stock by establish
ing nurseries at safe distance from
susceptible elm trees or clearing out the
elms from the vicinity of large nurs-
cries.
CHAS. d. WOODS,
Director