PART IV.
SUDAN BOLI: WORM (Diparopsis castanea)$
_ The CHAIRMAN (Mr. Fuller) read the following note by Mr.
Haines: —
Both sprayings and dustings by lead arsenate, calcium arsenate,
Paris green, ‘calcium cyanide, sodium fluosilicate and Bordeaux
mixture have been tried very extensively at various times during the
past seven years; and all, except Bordeaux mixture, have given
negative results. Last season’s experiments with calcium arsenate
dust gave absolutely negative results; in nearly every instance the
controls gave more seed cotton per acre than the treated plots, in
applications ranging from one to six. Also the cost of treatment was
considerable—in many cases absolutely prohibitive. With Bordeaux
mixture, more promising results were obtained but not promising
enough to warrant recommendation. Increases in yield, ranging
from 30 lbs. to 250 lbs. of seed cotton per acre, were obtained. It
1s certain that spraying and dusting, as it is done at present, is not
a success. At present it appears that our only hope of success lies
with Bordeaux mixture, but much more must be learned first about
method of application and effect on boll worm and other pests,
and on diseases. It is not yet clear exactly what effect
Bordeaux mixture has on the boll worms alone. My several years’
experience with spraying and dusting for boll worm control has made
me very doubtful that it will prove to be an effective remedy. Basing
my statement on the data at present available, I can say most
emphatically that I am not prepared to recommend this method of
control; as a whole, the results obtained have been most discouraging.
I might add that our laboratory experiments on the effect of calcium
arsenate on the larvae of the Sudan Boll worm seem to indicate that
this poison has no effect, in that the larvae reject the poisoned rind
of the cotton boll.
Mr. MILLIGAN did not think that it was satisfactory to base
results on yields alone in the spraying with Bordeaux mixture: such
experiments can only give rough indications. He would like to see
the organisation of spraying experiments with Bordeaux mixture
carried out on broader lines. He further said that he was strongly of
opinion that no stone should be left unturned in an attempt to combat
this pest on cotton.
As to spraying and dusting, as methods of control, they did not
seem to have any definite figures: spraying would be difficult,
especially in South Africa and in places where there is a scarcity of
water. Experiments, however ,should be continued, and he was
anxious to know whether any results had been obtained by means of
trap crops. His Section had had no information on the subject.
Mr. SMEE had conducted one experiment on these lines but had
got no results, as he could not get the Sudan Boll worm to feed on
any other crop. Cotton as a trap crop had not been tried. Mr. King
was working on these lines but his report had not been received
Mr. HARDENBERG had known of a case in Portuguese Bast
Africa where a planter took the trouble to hand-pick the first infested
bolls; and the planter was of the opinion that hand-picking, in that
Y See also page 177.

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