The Seattle post-intelligencer. [volume] (Seattle, Wash. Terr. [Wash.]) 1888-1914, 1891-07-01
HOW TO KILL THE HOP LOUISE.
Professor Riley Says the Vines Must Be
Burned After Picking.

burned After RtckinB'
From Government Bulletin.
1have been examining plum thickets In TINS
(Lsne) county, in the vicinity OF hop yards ana
l find thousands of eggs of the hop louise (Phoro-
donl. Further, / have found earlier In the
autumn specimens of Phorodon on plums near
by and also Others q number OF miles from any
hep field. The variety of plurns upon which so
many eggs were found is knowd as "Petersons
Seeding" or "Peterson's Drupe," the nearest
approach to wild plum which we have here.
have advised the burning of these useless
thickets. Doubling Thomases say: slow can
you prove to US that those eggs on the plum are
not those OF some other aphis, plum aphis for
instance" And reply by saying that the plum
aphis does not begin 10 be abundant
enough in this section to produce tenth
part as many eggs; further, / fall back
upon the result of your Investigations in Europe
and America and also the fact that have OBJ
served Phorodon on the plum in large Numbers
this fall earlier in the season. I cannot show
them an egg of the Plum Aphis for comparison,
even If there is difference between the two.
Neither can with certainty obtain any plum
aphis eggs Could you conveniently send me
few eggs of this latter insect now? Upon my
inquiring OF them, hop growers, as to whether
they burned their vines Immediately after gath
ering the fruit, they invariably replied that they
did do that, but further inquiry ELECTED the
fact that said burning does not take place until
after the vine is all withered, when the louise
has left them. pointed this out TO them and
urged very strongly indeed their burning the
green vines Immediately after picking, as they
pick Does not this agree with your idea?
The fact that have found the Phorodon on
plums at least two miles from hops, leads me to
ask if understand your statement in your sum-
mary QSS3 Report) that "they do not migrate
readily from one hop yard to another" found
no eggs upon the following trees, though grow
ing among the hops: Bradshaw plum, yellow
egg plum, Italian prunes, Petite Bows. Two
damsons growing in the same situation were
not examined, but will be shortly, and the re-
suit with cuttings sent to me at Corvallis.
! should be gratifed to hear expressions of your
opinion on various points in this letter, and If
you could oblige me in the particular of Plum
Aphis eggs should appreciate the favor.-E L.
Wdshburn, Corvallis, Or, November 50, 1890.
REPLY.-I am much interested in you letter
of the S0th ult. and am pleased to learn that you
have so speedily fulfilled my predictions with
regard to the stocking of plum by return mi
grant Phorodon. Your information regarding
the variety of plums infested also interests me.
AS to distinguishing the eggs of Phorodon from
those of other plum alternating Aphidid9,
can hardly assist you by sending you authentic
eggs of what you call "Plum Aphis," for the
reason that there are several plant lice which
oviposit upon plum in the fall in the Eastern
states and IN England, and am not sure which
one, if any of these, you have in your vicinity.
1t 10 safe to say, however, where Phorodon has
been migrating in its usual numbers from hop
to plum that its eggs will so vastly exceed in
number those of any other species that
you cannot fail to recognize them. l may
say, however, that the eggs of Aphis pruai,
which somewhat resemble those of Phoro-
don, are larger and rather lighter colored.
/ certainly indorse your advice as to burning the
old vines Immediately after picking, as this is
what have myself recommended. You have
misunderstood my statement which you quote,
to the effect that the lice do not migrate readily
from one hop yard to another. To be more ex-
plicit, migration from hop yard to hop yard is
through wingless individuals, which is slow or
even impossible at long distances, while the
winged return migrant instinctively quits such
fields for prunus The statement above referred
to means just what it says and nothing more,
and IN my complete report tnot yet published)
/ have called attention to the fact that the re-
turn migrant generations in the fall will fly long
distances in search of plums. This fact was also
brought out in Mr.. Towards notice of my in
Vestigation in the CoUstry Gentleman of Novem-
Der II. 1887. In other words, the non-tendency
to migrate to any distance holds only as between
hop yards.