PART IV. 175
of value, it can be stated that the only information on implemental
cultivation and rotations is applicable only to countries where the Pink
Boll Worm undergoes a resting period, and mainly to places where
cotton is grown by irrigation. The experiments of Williams and
Bishara, in Egypt, conclusively proved that the greater the depth the
bolls containing the resting larvae are buried, the fewer survive; the
survival at 30 cms. being nil. Secondly, the wetter the land is kept
during the winter, the fewer are the survivals next spring;
consequently, Bersim (Egyptian Clover), which is frequently
irrigated, is a much more suitable crop to follow cotton than the usual
alternative in Egypt, namely, wheat, which receives much less water.
But where cotton is grown under rainfall conditions and in countries
where the resting stage larva of the Pink Boll Worm does not occur,
it does not seem likely that rotations would have any effect one way
or the other.
(e) SPRAYING AND Dusting. From the nature of the life history
of the Pink Boll Worm it cannot be attacked by spraying and
dusting. It is just possible that, if the adult moth (as do many other
moths) drinks dew, the dew might be poisoned by a calcium arsenate
dusting, but it seems unlikely that this would be a practicable means
of control.
(f) Trapping Apurts. The Pink Boll Worm (in spite of
numerous statements to the contrary) is readily attracted to light.
Willcocks in Egypt caught 19,000 moths with 18 traps in an acre of
cotton in three months, but although the infestation was somewhat
less in the trapped plots than in the controlled ones, he did not
consider the use of light traps an economical measure. No information
is available in regard to trapping by bait.
(g) and (h) HaxD-pICKING OR COLLECTING LARVAE IN THE FIELD,
AND TRAP-CROPPING. These methods are considered to be
impracticable.
2. With regard to the question raised by the Department of
Agriculture, Uganda, concerning the measures adopted for the control
of Pink Boll Worm, and the prevention of its spread, it is understood
that this enquiry aims at securing from Tanganyika some measure of
reassurance, and Mr. Ritchie submits the following remarks:
There are two areas in Tanganyika Territory, near the Uganda
border, in which cotton is grown, namely, Bukoba and Mwanza.
These areas are not infested with Pink Boll Worm, and there is no
connection between them and other areas in Tanganyika Territory in
which Pink Boll Worm has been found. In their own interests the
Tanganyika Government are making every endeavour to prevent the
spread of Pink Boll Worm to the Bukoba and Mwanza areas, and
there appears to be every probability that the measures taken to this
end will be effective, as there is a buffer zone between the two areas
—some 200 miles of barren country clear of cotton.
The reply to the Conference might, therefore, read : —
Tanganyika is endeavouring to prevent the spread of Pink
Boll Worm of Cotton from the infested area of the coast and
central region to the clean areas of Bukoba and Mwanza, which
are adjacent to Uganda.