Feb. t, 1895.] 
THE TROPICAL AGRICULTURIST. 
5°5 
I* ig a flat pale yellow sca'e, and is very destructive. 
The yello w scales is otten mistaken for the red scale 
(A., aurantii) which it closely resembles, but while the 
latter is found upon fruit, leaf and branch, the yellow 
ecala is seldom seen elsewhere than on the leaf and 
fruit; and furthe -more, it has aChalcil fly parasite 
which will not to ich the red *cale. This Chalcid fly 
lays its eggs beneUh the scale, and the ymng Chalcid 
being the more active devours the young citrini before 
they see day ight, then boring a hole thr mgh the 
shells escapes. The owners of trees infested with 
yellow scale woild do well to obtaiu some of the ; e 
parasies from San Gabriel orchards, where they are 
reportel to be clearing the trees of yello v scale. 
The purp'e scale (Mytilaspis citricola] is a Florida 
pest o' a raps; pernicious character. They have been 
trvin* for years 'o destroy it, without much success, 
and now it has bee 1 brought into our State, probably 
on nursery stock. It hn not a very strong lodgment 
here yet, and it -hould be th 1 duty of every orchard 
owner t > s 'e that it has no chan'e for that. It is 
a long, curved scale of pirplish hue, found only on 
citrus trees and most abundantly i > moist regions. It 
develops from the eggs to maturity in about 60 days, 
making its possible increa e enormous. There i3 no 
known natural enemy, and our o.ily hope is that in 
our dry climate it will not flourish. 
There is another coccid that is just beginning 
work upon our orchards. It is not a true 3ca e insect; 
it is rather a species of th> mealy bu^ that has 
been so troublesome in the east upon shrubbery and 
greenhouse plants. It is a soft, fleshy insect thickly 
covered over with a white wooly substanca s-creted 
through the pores. These have been fmndlociting 
on orange trees in this valley. What they in end 
to do, time only can tell. Against these «s against 
all other orchard pests we must be coistintly upon 
our guard. 
An acknowledgment of gratitude is due all our 
inspectors for their faithfu' performance of duty, by 
which, even at the risk of personal enmity, they 
have protected us well from the introduction of new 
seal-?. That some scale msec s have escaped their 
wat hfuluess is iuevita-le, that so few have is our 
rej >iciug. Tie du y no>v lies with m to refuse all 
nursery stock infested with anv kind of scale insect, 
and to exterminate by ev.-ry known means the pe ts 
already ••mong us. With clean fruit and healthy 
trees, Southern California can challenge the world 
in fruit producti >n. 
Prof. A. J. Cook, Claremont. — I want to say here, 
incidentally to •-•rowers to use London purple in 
preference to Paris grae i as an insecticide. The 
London purple is not so apt to be adulterated, is 
t-heiper aud equally as etfieient. But always be 
sure and use it with a little lime. The usual for- 
mula is one pound to 200 gallons of water; tree* 
are scarcely ev r injured when lime is added. I 
am not in 1 he habit of a Ivertising particulu - brands, 
but in this case will depart from the rule to s ate 
fiat the Hemouwiy's London purple I have always 
found reliable and of uniform strength. 
The Pre-ident. — I learn from newspaper reports 
fiat of the thous mis of parasites (Rhizobiiu ventralis) 
of the black sea e (L 'caui m oleae) liberated in San 
Bornardi 10 county not a single specimen is to be 
fouud. Is th it correct '! 
Phof. Cook. — Tne statement is hardly literally true; 
there are some 10 be found there now, uotably on 
Mr. Wright's pla-e. I hope that the Rhizobii will 
yet get such a start as to be able to conquer the 
blacK scale, though it must be admitted that we 
have met with a disappointment in the discovery 
th it there are a number of predatory insects feeding 
o;i the Ruizobii. Tne laje witig lly ^Chrysopa Cali- 
fornia*) is one, and besides this there is aother as 
yet unidentified which is dastroying larno numbers in 
the larva state. It is to be hoped that these increase 
in a smilier ratio than the Rhizobii) particularly 
a. ce- 1 tin seasons of. the year, and that the Rhizobii. 
being rapid bre tiers, will be found eventually to 
ae somplun what we all so much desire. They have 
been distributed hereabouts in large numbers, and 
while the outlook just at present is not over-en- 
couraging we still find them in a number of places. 
Allowing for the fact that it required two years for 
them to become established at Santa Earbara we 
have hopes they will do equally as well here in the 
course of time. 
Mr. W. B. Collins, Ontario.— In San Bernardino 
country but very f-w of these parasites, inde-d. I do 
not think I strain the truth when I say that practi- 
cally none are to be found. Of all the colonies 
planted in and about Ontario last spring, the ento- 
mologist—Mr. Craw— of the State Board of Horti- 
culture after a diligent search made last July found 
only one single beetle. A similar hunt a few days 
failed to reveal any beetles or larva of the Rhizobii 
in the olive orchards of Prof. Dwinelle or Mr. Lord, 
where Mr. Craw liberated several thousand on 
September 20. In addition to those which were 
colonized on behalf of the country after repeated and 
urgent requests by the board of supervisors, indivi- 
duals at their own expense have secured colonies. 
It ii safe to say that upwards of 100,000 beetles have 
been placed in Sin Bernardino county, sufficient 
cer ainly to test the bug. From the time they were 
liberated in the several orchards there has been a 
decrease noticeable for the first three or four weeks, 
after which one or two of the parasites could be' 
found in a few scattering places. During an exami- 
nation made a few days ago by Mr. Scott, \fr. Looney, 
myself and others in a few orchards in Pomona 
whn-e large numbers had been placed not a single 
beetle or larva was to be found. This is to "he 
regretted, but it is not wise to shut our eyes to the 
truth. Of all the colonies placed in Los Angeles and 
Sau Bernardino counties not a single tree has been 
cleaned of the black scale as a result of their pre- 
sence to my knowledge; nor are they to be found 
anywhere in anything like appreciable numbers. This 
is not a mere assertion, but a fact experienced by 
all grow -rs hereabouts who have attempted to intro- 
duce these ladybirds in their trees to subdue the 
black scale. 
Mr. Messenger, Pomona.— As an experiment Prof. 
Oook and myself liberated about 4,000 of the Rhizobii 
on a couple of trees badly infected with black scab? ; 
r cent examinations failed to reveal the presence of 
the ladybirds in any stage. In fact there was no 
evidence of their existence. 
Prof. Cook.— When I secured the colonies from 
Santa Birbara I supposed we had three varieties 
of Riizibii — R. ventralis, R. debilis, and R. Two- 
womabae— but an examination showed this to be an 
error. What we presumed to be the latter two turned 
out to be a scymnus. 
The President.— In the absence of artificial means 
of freeing our orchards of scale and the presence of 
parasitical and predaceous insects, can it truly be said 
that the sca'e is bein< diminished by the parasites, 
or are injurious insects on the increase? 
Pi:of Cook.— Judging from my short per'od of 
observation— for I have not been among you scarcely 
a year— I should be inclined to say that the scale 
is being gradually growing less, though I do not 
attribute this disappearance to any one parasite or 
even a single g oup. All predace'ous insects assist 
to carry on the war of extermination, some of course 
more than others. But for these beneficial insects 
I believe fruit production would almost be impossible ; 
at -ny rate unprofitable. 
The President.— Would you recommend the aban- 
doning of sprayin - or fumigation to eradicate insect 
pests, and rely s dely on nature's remedy ? 
Prof. CooK.-That depends. In the case of the 
white >cale it would certainly be a waste of monev 
to spray or fumigate. Regarding other pests, grow- 
e s assure me that it pays them to do so. Of course 
when you kill the i jurious insects ou your fruit 
trees you also destroy the beneficial ones. If Ky 
abandoning artificial methods we could ,0 protect 
O'.r insect friends until thev shall be suffieiehtly 
slron- to overcome the scale is a p.obleni that many 
just now are anxious to solve. It seems to meltba't 
this is a matter the wide-awake .and practicaljjorch- 
ardist must settle for himself. -Much depends" on 
ci.cuinstaucc 1 11 1 , a litions; there we undoubtedly 
