32 BULLETIN 918, U. S. DEPARTMENT OF AGRICULTURE. 



SUMMARY OF DAMAGE BY THE PINK BOLLWORM.* 



(1) Loss in squares and blooms: 26.8 per cent of the squares and 



blooms shed. 



(2) Loss in pickable cotton: 



Lint: Deterioration in quality. 



Seed: Is reduced 6.9 per cent in weight; quantity and 

 quality of oil also reduced. 



(3) Loss in nonpiekable cotton: 19.98 per cent of entire crop ren- 



dered unpickable. 



The damage to the nonpiekable cotton and the loss by weight in 

 the seed in the pickable cotton can be reduced to a monetary basis. 

 Assuming lint to be worth 30 cents per pound and seed worth $60 

 per ton, the value of 500 pounds of lint would be $150 and 1,000 

 pounds or § ton of seed would be worth $30, or a total of $180 per 

 bale. For every bale picked there is 19.98 per cent of the seed and 

 lint left in the field as nonpiekable cotton, or, in other words, the 

 amount of cotton actually picked represents only 80.02 per cent of 

 the crop if no pink bollworms were present. Then the value of the 

 crop produced would be $224.90 rather than $180. The loss of 

 19.98 per cent of the potential crop ($224.90) is equal to $44.93 per 

 bale. In addition to this there is 6.9 per cent loss by weight in the 

 seed of the pickable cotton (which represents the 80.02 per cent of 

 the bale not included in the 19.98 per cent loss or nonpiekable cotton), 

 which amounts to $2.07. Therefore the total loss is $47 or 20.89 

 per cent of the value of the bale. 



The calculable loss that can be specifically stated on a definite 

 percentage basis is 20.89 per cent. In addition to this figure there 

 should be added the losses incurred in the shedding of the squares, 

 deterioration in the quantity and quality of the oil in the seed, and 

 the weakening and irregularity of the staple in computing the total 

 damage caused by the pink boll worm. 



FOOD PLANTS. 



While cotton (Gossypium, spp.) is by far the most favored food 

 plant, a number of other plants have been recorded as host plants of 

 the pink bollworm. Maxwell-Lefroy (2) records a species of Hibiscus 

 and the oily seed of trees (species not given) in India; Fullaway (3) 

 reared a single specimen from milo (Thespesia populnea) in Hawaii; 



4 Damage during 1920. — The damage to the Laguna crop by the pink bollworm was unusually severe 

 during 1920. Frost did not come in 1919 till very late and this was followed by a mild winter, which 

 allowed a large percentage of the hibernating larva? to pass the winter successfully. The fields were ex- 

 amined during the latter part of June, and it was very evident that the infestation in squares and young 

 bolls was heavier than it had been in 1918 or 1919. The cotton was also further advanced and was growhig 

 rapidly, with very good prospects for a large crop. About this time there were severe outbreaks of 

 aphids {Aphis gossypii), thrips, and rust (Aecidium gossypii) which checked the growth of the plants 

 and gave them a setback from which they never recovered. This caused the plants to produce very few 

 bolls, and the infestation by the pink bollworms and the percentage of loss have consequently been very 

 high. Estimates made in November showed that the pink bollworm had injured 31.3 per cent of the 

 crop so badly that it was rendered unfit for picking and that there was 7 or 8 per cent additional loss 

 attributable to the insect by the lowering of the quantity and quality of the pickable cotton, or a total of 

 38 to 39 per cent loss of the crop. 



