EFFECTS PRODUCED BY PINK BOLLWORM ON THE YIELD OF COTTON SEED. 307 



fart of the damage now found to be due to Gelechia would informer days have been equalled 

 and in some years even surpassed by damage done by Earias. It is true that Gelechia 

 has compelled earlier cleaning up of the fields, and has nearly done away with the 

 possibility of a third picking. This condition of things was, however, quite 

 independently of bollworm or pink bollworm, bound to follow the introduction of 

 Sakellarides cotton, which is an early maturing variety. Under former conditions 

 bollworm attack was principally on the second and third pickings, and called for 

 early maturing cottons as a remedy. Gelechia has greatly accentuated this demand 

 for earliness in ripening and is forcing the cultivators, with or without their knowledge, 

 in that direction in their seed selection. A still earlier maturing cotton is however 

 required, and any such, if developed, will by reason of this character alone be able to 

 compete advantageously with all otherwise equally good but later maturing varieties. 



Notes on Observations made in 1917-1918. 

 A. The Rate of Increase of Gelechia in 1917. 



During the summer of 1917 a considerable amount of information was gathered 

 on the infestation of cotton-plants by Gelechia. An experiment was carried out 

 at the Government farm at Gemmaiza, in which at first one hundred and later 

 fifty cotton-plants were uprooted and examined daily for pink bollworm. 



That the material collected in this manner was really representative for the 

 conditions in the field can be seen from figure 5, which illustrates the budding, 



500 



450 



400 



350 



300 



2SO 



200 



150 















\ 











B 







if 





V 



v. 











Flo\> 

 Green i 







/; 



















Ripe 6 



oils 



— 



// / 





\ 

 \ 

















l:l 

 1 : 1 





\ 

 \ 

 \ i 

















11 / 

 i:l / 

















• 

 • 





i ■/ 

 / / 







/_ . 



- **\ 



\^y^ 







s 





f f 









\ 



\ 







jr ' 



r / 



- ■*" 













\ 

























I 

 Weeks 



Fig- 5. 



10 



Bud, flower, gTeen boll and ripe boll curves for the Gemmeiza 

 experimental field. 



flowering, boiling and ripening curves calculated from the data collected. As this 



represents purely botanical work, and was only examined by way of control, there 



is no need to enter into details of the manner by which the weekly accessions of 



buds, flowers and bolls were calculated. It is enough to point out that the curves 



obtained show remarkable agreement, seeing that each position fixed has been worked 



out with the spoils of plants used for that date only. 



(C541) c2 



