The Indianapolis journal., 1889-07-03
THE GREEN MIDGE.
Official Report as to the New Wheat Parasite
Vigorous Grain Damaged Slightly.

To the Editor of the Indianapolis Journal:
Acting under instructions from Hon. J.
NJ. Rusk, Secretary of Agriculture, have
spent nearly two weeks in the southern
portion of the State, in the investigation of
the grain aphis. which, just now, is excit-
ing so much comment among grain growers
of this and other States. So far as have
observed, the greatest damage caused by
this pest has occurred in fields where the
soil was poor and the plants thin on the
ground or the grain had been backward in
maturing Such fields have been damaged
from % to 20 per cent. In fields where the
ground was fertile and the grain vigorous
and forward, the damage has. as a rule.
been slight SO far as can now be Observed.
Threshing may show sllghtly greater
injury than now appears. Little or no
further damage will be done in the
southern and central portions of the State.
at least to the wheat crop. What the oats
crop will suffer it is difficult to determine.
Copious rains add vigor to the plants, and
work adversely to the grain pest. Besides
this small, slender, brownish fly is de-
strOying the grain aphis by the millions.
These minute friends puncture the bodies
Of the pest and deposit therein an egg,
strOys them, the body of the victim assum-
ing globular form and turning brown.
The heads of grain everywhere are covered
with these parasitized individuals, and in
some fields, at least, Outnumber the liv-
ing aphis. There is little dOubt but that
these industrious little friends are doing
much to protect the oats from destruction.
| 1t Is impossible at present to estimate the
| damage that will result throughout the
| State. as the weather, condition of grain
| and number of parasitic enemies of the
| grain aphis all figure in the problem, but
| there seems to be some ground for the hope
| that the damage will be so much reduced
by these agencies that. though severe, there
| will not be total loss in any case, and a
comparatively light loss in the majority of
instances.
The insect causing the trouble is the
grain aphis, siphonophOra granaria Kirby,
| and we received it several weeks ago from
| various parts of southern Indiana and
| Illinois. The species is OF foreign origin,
fields of Europe is enveloped in obscurity.
| If 1T occurred in destructive numbers
during the time of Linnaeus either its
| ravageS were not of sufficient magnitude to
| attract his attention or else he considered
| it as some other species. the latter theory
| being extremely doubtful, as he was firm
| believer that every species confined itself
to single species of plant. Fabricius, in
| 1894, describes species as aphis avenB, he
| probably having found it on oats. In 1877
Kirby observed what probably was the same
| species infesting wheat, oats and barley and
gave. it the specific name of granaria.
| Still later the species was named cerealis
by Kaltenbach. and hordei by Kyber.
| Curtis, speaking of this species, gave no
| mention of its occurrence in England prior
TO 1897. Just when the species was intro
possible to determine. Harris does not
| even mention i6 in his writings In his
sixth report, published in 1861, Fitch states
that in searching for injurious insects dur
;v,rv oxyio hA ho1 ohc yn1 ha
species repeatedly. but only in very limit
| ed numbers and scattered about on the
leaves and stalks of grain, in a manner to
cause him to regard their occurrence of no
ceived by him the previous year uS60) he
opined that the species had. in some locali-
ties, begun to multiply exces-
slvely. At present we have no in
America in numbers sufficient to attract
attention. Within the last twenty years
these insects have occasionally been quite
numerous, but have rarely caused any
son has, up to a short time, been very ia
vorable to their development, but the re-
| cent rains will have a tendency to prevent
further increase in numbers and depreda;;
continue dry. they are likely to do consid-
cradle damage in the northern portions of
the State, as they increase with astonish-
ing rapility. DR.. Fitch estimated that
| single Iefnale, uuueF IaVOfaDle cffcum-
stances. might. within twenty days, be the
progenitor of upward of two million indi-
viduals. The young themselves repro
duce within three or four days, and
these again become mothers in about the
same length OF time. They do not confine
themselves to wheat alone but depredate
upon all kinds of small grain. including
oats. They occur on grain IN the fall and
again in the spring, but where they pass
the time between harvest and the appear
ance of young grain in the fall. is not
known. They damage the grain plants but
little. but do their chief iniury to the ker-
nel which they cause to shrink. They are
prey ed upon by the lady beetles and sew
eral minute hymenOpterous parasites, and
/ have noticed parasitized individuals
among nearly all that have received.
+. NJ. WEBSTER
Special agent United States Department of
Agriculture, Division of Entomology