Z PART 1V.
hopper Delphaz sacchernora.
| This suggestion was accepted by the Section.
4. Mr. Hardenberg stated that he was experimenting with
Nicotine dust and Bordeaux mixture in the control of Jassids.
SECTION II.
THE PINK BOLL WORM (Platyedra Gossypiella).
A great deal of discussion centres around Pink Boll Worm,
particularly as between Entomologists, in whose territories the pest
1s at yet unknown and those in whose territories it is present.
Unfortunately, the discussion was of a limited character, owing to the
fact that many territories in which the insect is known or supposed to
exist are not represented at this Conference.
(a) Answers to Questions.
1. The Entomological Section has been to considerable trouble
to formulate, to the best of its ability, replies to the series of questions
put forward by the Empire Cotton Growing Corporation, in so far as
these questions relate to the Pink Boll Worm.
I am now referring, in particular, to the Agenda, Category VII.,
item 6. The replies are as follows:
(a) ConrroL BY Narturan Enemies. There is no effective control
by natural enemies. In Egypt one of the parasites present, Pimpla
roborator, does become common at the end of the season; and it is
more than likely that by a thorough knowledge of its bionomics its
numbers could be increased early in the year, thus checking the rapid
increase in the Boll Worm population. But it can definitely be stated
that, without a great deal of research. nothing much can be expected
from natural enemies.
(b) and (i) ErimiNnarion or Foop Pranrs. While recognising that
further work is essential in the determination of native host plants, it
can be stated that the value of the elimination of alternative food
plants depends on the life-history of the Boll Worm in any given
country; this is determined by the climate. In countries with a
definite winter, where cotton is a summer crop, the Pink Boll Worm
spends the winter as a resting-larva, usually in a ‘‘ double seed *’ i.e.,
two or more half eaten seeds spun together. Under such conditions
it is these resting larvae 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 larvae 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.
(¢) and (d) IMPLEMENTAL CULTIVATION AND RoraTIoNs. While
recognising that it might be worth while to experiment, with a view
to ascertaining whether sustained submersion bv irrication would be

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