239

ENCLOSURE TO PART 1V.
as a resting-larva, usually in a ‘‘ double seed,’ i.e., two or
more half eaten seeds spun together. Under such conditions
it 1s these resting larvee in the numerous old bolls that fall
to the ground and escape destruction, which carry on the
race to the following year; and the elimination of alternative
food plants, which probably means nearly or quite all
Malvaceous plants, would probably not be economically
worth while. -But when there is no definite winter, and the
boll worm breeds continuously throughout the year in a
succession of short-cycle generations, the destruction of
alternative food-plants, in combination with a close season
for cotton, is absolutely essential; the moths emerging at
the end of the cotton season will then find nowhere to lay
their eggs, and as the larvee are unable on account of the
climate to assume the long-cycle condition, a fair measure
of control should be assured by these methods alone.
ec) and (d) Implemental cultivation and rotations. While
recognising that it might be worth while to experiment with
a view to ascertaining whether sustained submersion by
irrigation would be 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 were buried
the fewer survived; the survival at 30 cms. being nil
Secondly, the wetter the land was kept during the winter,
the fewer were 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.
Spraying and. Dusting. . From the nature of the, life
history of the Pink Boll Worm it cannot be attacked by
spraying or 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.
Trapping, Adults. 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) Hand-picking or collecting Larve in the Field,
and Trap-cropping. These methods are considered to be
impracticable.