PART IV.
planted between young coconuts being 1,100 lbs. seed colton per
acre on a plob of 50 acres. In this way they had avoided the bollworms
 and other causes which tend to decrease the yield. If irrigation
could be applied during the months of August and September when
necessary, they felt sure that higher yields could be obtained, and
thus cotton growing would be made more profitable.
Mr. KIRBY thought that, in this connection, one point should
not be lost sight of and that was the production of early maturing
varieties of cotton. Cotton specialists and entomologists might
collaborate in an attempt to provide a ‘‘ pest-avoiding type.
Mr. DUCKER said that, from his experience, it seemed necessary
in Nyasaland to evolve two distinct types to suit the different climatic
conditions. ~~ Experiments were being made on these lines, and he
hoped that more information would be available next year.
Mr. KOCH stated that similar experiments were being carried on
in the Union of South Africa.
APHIDES.
The CHAIRMAN (Mr. Fuller) read Mr. Haines’ notes*, and said
that this question had not been fully discussed by the Entomological
Section, as it was suggested that such discussion should be postponed
for the Joint Meeting of the Cotton and Entomological Sections.
Taking the question of Aphis first, he thought that more work
should be done on the natural enemies on a field scale, as dusting and
spraying had not proved economical.
Mr. HARDENBERG said that in Portuguese Fast Africa they
did not consider Aphis to be a serious pest of cotton; it only damaged
the young plants of 6 ins. to 8 ins. high, and when the plants had
grown to 18 ins. in height they had outgrown the attack. Ie
considered the damage to be negligible on mature plants.
Mr. MILLIGAN agreed with Mr. Hardenberg’s opinion.
Mr. HARGREAVES said that there was a big variation in the
incidence of Aphis attack correlated with the times of planting. Older
plants suffered to some extent. He agreed, however, that the
damage was most serious in the case of young plants.
The CHAIRMAN (Mr. Fuller) was of opinion that it depended
greatly on the season: he said that you could have an Aphis season
or not, and that the point was whether any control by planters was
feasible or not. No doubt Aphis could be controlled, but it seemed
to resolve itself into a question of economics.
Mr. RITCHIE stated that in Tanganyika the Aphis attack was
at its worst from the middle of May to the end of June—just after the
heavy rains. The main controlling factor was an indigenous fungus;
when this got a hold the field was cleaned up.
The CHAIRMAN (Mr. Fuller) said that there seemed to be no
doubt that there were several species of Aphis on cotton, and the first
essential appeared to be to investigate the various species and the
effect on them of climatic conditions.
Mr. MILLIGAN would like to see further experiments done on
the lines of Mr. Ritchie’s statement.
* See page 173.

180