The record-union., 1891-02-28
PARASITES.
Important Paper from the Board
of Horticulture.
Internal Enemies of the Yellow Scale
Discovered in the San Gabriel VAL
ey-Recommendation and Notes.

From B. NJ. LeLong, Secretary of the
State Board of Horticulture, we have the
ollowing important paper, submitted to
he Board by Alexander Craw, Quaran-
ine Officer and ex officio Entomologist:
In the year 1872, an extensive orange
grower in the San Gabriel Valley, pur-
chased several small orange trees at 4 San
Francisco tree depot, and planted them in
his grove with the intention of budding
from them, if the varieties proved desira-
bic, as previous to that most of the citrus
trees in California were grown from seed
and allowed TO bear fruit as seedlings.
The trees were found to be infested with
scale insect of species of lAspidiotus,
which spread to the adjoining orange
trees, and their presence was detected by
the mottled, siekly appearance of the
leaves and fruit. A determined effort was
made to check its spread, and, if possible,
stamp it out, ard the trees in the infested
portion of the grove were cut back, the
branches burned, and the trunks and
limbs scrubbed; but after all this heroic
treatment enough scales escaped TO intest
the district.
To distinguish it from the ''brown
SCALE" Lecdnitm hcSpeIIdlm, and the
''black scale,'' l.. oteoc (the only scales
that were then attracting attention in the
State). it was named the "red SCALE" from
y
sidered identical with the red scale of
Australia, ASpidiotdts dIraRti. Maskell;
but quite recently specific differences
have been observed that prove it distinct,
and it is now known as the ''yellow
SCALE" Aspifiiot1Gs cit9-iaauS, Coquillett.
Various solutions were sprayed on the
trees; sulphur and other substances We're
inserted under the bark, and the small
roots were severed, and to the ends Lead
ing to the trunk walls were placed con-
tanning chemicals of various kinds, i'll tine
hope that the roots would take the chemi-
calls up and destroy the scales; but in a
great many instances the trees were de-
stroyed instead, and others injured and
made unproductive by reason of the
cauStic or greasy properties of the washes
then used. In the meantime the scale
was slowly but surely spreading, until
now it is found III nearly all the orange
growing sections of the valley and ad-
joining foothills.
In the spring of 1889, Mr.. Cogswel, of
the Sierra Madre Villa, informed me that
the scales We're not as numerous in his
grove as they had been. He brought me
branches infested with yellow scales,
from which Matched n number of very
small chalcid flies; this parasite, how
ever. .!had been discovered by Professor D.
w. Coquillett two years previous, in the
extensive groves of \. B. Il A. S. Chap
man; but as the Improvement in the con-
dlton of the trees was more noticeable in
the Cogswell grove, ] am Of the opinion
that they spread from the latter to the
Chapman and other orchards
Various theories have been advanced
for the disappearance of the yellow scale
in that section; the principal one is. the
excessive rainfall of the winter of 1SS9-90.
But this theory can easily be exploded by
the fact that we have had very heavy
rains IN previous winters, and again, the
lH1nrOVpnnnf nNrjnna lAin anI
mented upon previous to the winter of
1SS9-90. II the rains had caused the de-
stTuction OF the scales, why is il that the
decrease Is not all over the infested sec
ton? find that where the parasite has
only recently been found. or where I
have been unable to find them at all, the
yellow scales are as numerous as before.
1 have recently Matched them by tho hum
dred from scale-infcsted leaves taken
from an orchard wherein little over a
year ago the parasite was not known to
exist. The presence of such numbers of
parasitic insects-even if they are so
minute as hardly to be detected with the
naked eye-should be sufficient to con-
vince even the most skeptical that the
scales are succumbing to natures rem
edy"
The fact that the scales appeared to be
on the increase last fall can be accounted
Tor. That is the time when our scale pests
have every season shown the most in
crease, and that this was noticeable in the
orchards where the parasite has been at
WORK the longest, is not very remarkable
as we have had another identical case.
When the cottony cushion scale was sup
posed to be cleaned out of some groves.
and consequently there was no food for
the Peddiia cdrdiRdliS. the latter disap-
peared, and a few of the former that es-
capped increased and caused considerable
alarm; but they were soon destroyed
when the growers placed fresh colony
OF the ladybirds on their trees.
YELLOW SCALE PARASITE.
CoccophGguS citrinus. New species
(originaD.