i ENCLOSURE TO PART IV.
concerned and percentage of parasitism. It has been found that
bollworm parasites often attack species of leaf-feeders as well, e.g.,
Cosmophila aurigoides. The mortality of pupae in the soil is often
very high, but how much is due to enemies or parasitism has not yet
been determined.
EvimiNaTioN oF Foop-PLANTS.
Control by this means has not been attempted. It would be
impossible for the American bollworm since this species’ food-plants
are multitudinous and would be difficult for the spiny boll-worm,
since wild malvaceous plants are so numerous and so widespread in
South Africa. As for the Sudan bollworm, it would be impracticable
to attempt elimination of its food-plants until we know with more
certainty what these are. To my. mind, it is questionable whether
complete elimination of all food-plants of the Sudan bollworm would
solve the problem. We have not yet found an effective remedy for
this pest in the cotton fields; and until one is found these fields act
as reservoirs, which are as dangerous as the reservoirs in nature.
IMPLEMENTAL CULTIVATION.
No data is, at present, available as to exactly how effective this
method of control is, as it is extremely difficult to check up accurately
the results of any given cultural method. It is my opinion that a
careful study of this method of control should be made, if a
satisfactory way of checking up results can be found. It certainly
does not seem to be impossible to find a method of cultural operations,
perhaps combined with a close season and rotations, which would help
to check the bollworm pest.
RoTATIONS.
I have no statement to make on this method of control.
However, I think it a very important factor in bollworm control,
especially in conjunction with implemental cultivation and a close
season.
SPRAYING AND DUSTING.
Both sprayings and dustings with 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
application 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 to 250 lbs. of seed cotton per acre were obtained. It is certain
that spraying and dusting, as it is done at present, is not a success.
At present, it appears that our only hope for success lies with
Bordeaux mixture, but much more must be learned first about method
of application and effect on bollworm and other pests and on diseases.
It is not yet clear exactly what effect Bordeaux mixture has on the
bollworms alone. My several years experience with spraying and
dusting for bollworm 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

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