PART IV. 9
(2) That in some one centre an adequate staff should
investigate thoroughly the whole problem in all its aspects;
and that the Government of South Africa should be
approached, in the first instance, with a view to undertaking
this work.
#t That the programme of werk to be adopted should be
drafted by the staff of the centre chosen for the major
investigation.
*) That this programme should be circulated to Departments
of Agriculture in other cotton growing areas, with a view to
complementary work being undertaken by them.
OCCURRENCE OF MAJOR PESTS.
The CHAIRMAN (Mr. Fuller) read Mr. Haines’ notes* in regard
to the natural occurrence of major pests and their oceurrence under
conditions of cultivation.
Mr. MILLIGAN said that in the circumstances, he was satisfied
with Mr. Haines’ somewhat guarded reply.
SENHOR GRILLO made the following statement in regard to
the natural occurrence of major pests in relation to climatic factors:
For some years they have been growing cotton in the coastal belt,
north of the Zambezi, with unsatisfactory results. Cotton was sown
with the first rains, from December to February, and was picked
during the cold season—from June to August. The low yields were
principally attributed to insect injury, especially bollworms. This
experience and also a better understanding of the conditions of soil
and climate, induced them to try late planting as against the usual
practice elsewhere. During the last four years they have been very
successful. The comparative data were as follows:
EarLy PLANTING. LATE PraANTING.
Rainfall during the season, 45 ins. 20 ins.
Number of days with rain, 55. 35
Temperature declines from 83deg.F. Declines from 75deg.F. to 60deg.
to 60deg.F. F., followed by rise to 82deg.F.
Humidity during picking: 85 65
Predominance of pests:
During flowering and boll develop- During young stages of growth
ment: Spiny and American Boll- Jassid and Aphis: later on,
worm: before ripening Jassid; small attacks of Sudan Bolllater
 on, Aphis. worm.
Average yield, late sowing, on Lower Zambezi, N.W. during the last
four years, 650 lbs. seed cotton per acre. Average yield on Coastal
belt, late sowing, during the last two years, Z.H. 248 lbs. seed cotton
per acre, but this low yield was due to inexperience on the part of
the growers, for averages of from 600 to 800 Ibs. and more had been
picked on various farms, the maximum obtained in 1924 of cotton
© See page 172.

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