PART 1V. 
The CHAIRMAN (Mr. Fuller) observed that such work must be 
done by a mycologist. 
Mr. MILLIGAN would like to see everything tried which would 
help in any way to control plant diseases. If they knew that someone 
was working on these problems they would be more satisfied than they 
were at present. 
JASSIDS.* 
Mr. PARNELL made the following statement: — 
Jassid is a very important factor in cotton growing in the low 
veld of the Union of South Africa, and the production of a resistant 
type is one of the first objects of the Barberton Station. 
Cage experiments have proved that the Jassid (Empoascus Sp.) 
is directly concerned with the pathological condition under review, and 
is probably entirely responsible without the intervention of any disease 
organism. 
Speaking generally, the intensity of the Jassid attack on any one 
variety depends largely on the health and stage of development of the 
plant, it being least on a strongly growing immature crop. Various 
plant-foods appear to affect susceptibility only through their effect on 
the growing condition of the plant. The susceptibility of different 
varieties varies enormously, and the results of the last two seasons 
show that selection for Jassid-resistance is a most promising line of 
work. A decidedly resistant strain, possessing other good qualities, 
has already been obtained, and will be multiplied, provisionally, on 
about 200 acres in the coming season. 
The nature of the resistance of certain varieties is undoubtedly 
complicated. Some degree of tolerance exists, also some attribute 
which discourages the breeding of the pest. In the latter category 
hairiness, both as regards density and length of hairs, has been shown 
to be an important factor 
The CHAIRMAN (Mr. Fuller) agreed with the opinion expressed 
by Mr. Parnell. 
PINK BOLL WORM. 
~~ The CHAIRMAN (Mr. Fuller) read repliest drafted by the 
Entomological Section in answer to the questions asked by the Empire 
Cotton Growing Corporation. 
These were accepted, without discussion. 
~The Chairman reviewed the items of interest in connection with 
Pink Boll Worm, which had come under discussion by the 
Entomological Section. A resolution drafted by the Entomological 
Section in regard to a map of the distribution of the Pink Boll worm 
in Africa was submitted. It was approved with the suggestion that 
a note be inserted in the record to the effect that other arrangements 
should be made for the preparation of a map in the event of the Union 
(Government being unable to undertake it. 
See also page 173 
See page 174. 
See page 176. 
181