ENCLOSURE TO PART IV. | 
of cotton in South Africa for some years (see occasional notes in the 
Journal of the Department of Agriculture.) 
With regard to the other injuries attributed to Dysdercus it would 
be interesting to obtain the opinion of the delegates concerning the 
importance under field conditions of boll shedding due to stainer 
puncture, failure of the bolls to open normally and loss of lint due to 
injury to the seed by the same insects. Injury to seeds, affecting 
germination, appears to be of considerable importance in Southern 
Rhodesia during the present season. The seeds become very hard and 
shrivel to a noticeable extent. Whether the injury is purely direct or 
associated with the development of organisms has not yet been 
ascertained. The market value of the seed for crushing purposes is 
stated to be very seriously impaired, and much of it will apparently 
be unsaleable. It is thought that Dysdercus is responsible for this 
injury, but the question calls for investigation. It appears to have 
been generally noted that the first infestation of a cotton field with 
Dysdercus develops with great rapidity, and is due to invasion by 
adults which have matured elsewhere. Notes concerning the stage 
of development of the crop when this invasion takes place are not 
altogether in agreement. Thus Pomeroy and Golding in Nigeria state 
that the invasion commences as soon as the plants flower (R.A.E. 
XII., p. 67). Withycombe in Trinidad states that the stainers 
generally appear when the bolls are ripening and not before (R.A.E. 
XII., p. 548) and, elsewhere, that they are not attracted to the cotton 
plants in appreciable numbers until the bolls commence to open (Bull. 
Ent. Res., XV., p. 171). Observations in Southern Rhodesia to date 
are generally in accordance with the last two statements. 
Heavy shedding of the very young bolls, of course, commonly 
takes place previous to heavy invasion of the fields by Dysdercus. 
This shedding appears to be due to physiological causes, possibly of 
a similar nature to those causing the well-known *‘ June Drop ”’ of 
oranges in California, a phenomenon which occurs also in Southern 
Rhodesia in the corresponding season. Shedding due to Dysdercus 
attack must clearly occur at a later stage and the experience of the 
delegates as to its regular occurrence or otherwise, following the 
Dysdercus invasion, and its economic significance would be instructive. 
The points on which an expression of opinion by the Conference 
would be specially appreciated include the following: 
Have any of the delegates any experience of lint-staining 
occurring. under conditions where the agency of Dysdercus, 
or of other sucking insects, is not indicated ? 
- Have any of the delegates any experience of lint-staining 
which is apparently not due to either Bacteria or Fungi? 
Are any extensive outbreaks of bollrot, due to Bacillus 
malvacearum, Smith, in American ‘“ Upland ’* varieties on 
record ? 
What is the present position in reference to the association 
of Bacillus gossypii, Stedman, with Bollrot? 
Have any careful mycological studies been made of bollrot 
and lint-staining as occurring in Africa, apart from Marsh's 
work on stained Nyasaland cotton ? 
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