MINISTRY OF AGRICULTURE, EGYPT. 



Bulletin No. 13. 



(ENTOMOLOGICAL SECTION.) 



THE RATE OF INCREASE 

 OF THE PINK BOLL WORM IN GREEN BOLLS 



IN THE PERIOD 

 JULY TO NOVEMBER 1916. 



An investigation, the results of which are detailed below, was 

 undertaken with the object of ascertaining the frequence of Gelechia 

 larvae during the growing period of cotton, and more especially of 

 obtaining data concerning its increase in numbers relatively to the 

 number of bolls on the cotton plants, and if possible also its absolute 

 rate of increase. 



The greater part of the material used was collected by the 

 inspectors, sub-inspectors and moawimn of the Inspectorate Staff, to 

 whom thanks are due for the trouble taken in the collection of the 

 samples, which in some instances must have involved considerable 

 labour. 



The majority of samples asked for consisted of 100 green bolls, 

 taken at random and not necessarily from one field. One such sample 

 was required from each cotton-growing Markaz weekly. 



The samples, when received at Cairo, were examined in the 

 following manner. Each boll was cut in three slices in order to 

 ascertain whether or not it was attacked by boll worms. Records 

 were kept separately of the number of bolls containing Gelechia larvae, 

 Earias larva?, or of those attacked by other parasites. No attempt was 

 made, however, to ascertain the exact numbers of parasites per boll. 

 This limitation of the scope of the enquiry was necessary owing to the 

 immense numbers of bolls to be examined daily. The total number 

 examined exceeded 106,400 bolls. 



