﻿28 BULLETIN" 1374, U. S. DEPARTMENT OF AGKICULTUEE 



Table 22. — Average number of worms per boll in planted cotton and in zoca, 1921 



Date 



Planted 

 cotton 



Zoca 





0.14 

 .07 

 .67 

 1.31 

 1.53 

 3.20 

 4.08 



0.44 



July 2 



.63 



16 - - - 



1.47 



30 - 



2.79 



Aug. 13 - - 



1.95 



27 -. . 



3.30 



Sept. 10 - - 



2.72 



26. . --- - 



3.77 



Oct. 8 





2.02 









FOOD PLANTS 



Experiments were conducted and observations made by A. C. 

 Johnson on host plants other than cotton to determine the part these 

 plants may be expected to play in the perpetuation of the pink boll- 

 worm in the absence of cotton or its spread beyond extensive areas 

 in which there is no cotton. Dry okra plants containing a large 

 number of heavily infested pods were placed under a large screen 

 cage in the winter of 1921-22. The following spring both okra and 

 cotton were planted under this cage, the old stalks being allowed to 

 remain. The cotton bloomed about the middle of June and the okra 

 still later, but no infestation developed on either. 



On May 27, 1922, 200 okra pods were gathered from dry stalks 

 that had been in the field all winter. An examination showed 3 

 living larvae, 33 dead ones, and 1 pupal case. It is thus evident that 

 under Laguna conditions the larva can survive the winter in okra 

 pods on stalks in the field. In an okra pod, however, the larva is not 

 so well protected against cold as in a cotton boll containing cotton. 



Other malvaceous plants growing in the Laguna district were like- 

 wise studied with reference to their possible relation to the pink 

 boUworm as host plants, A larva was found in a bloom of hollyhock 

 {Althea rosea) as early as May 28 in 1922, and on June 7, 1921. Heavy 

 infestation of hollyhock was never noted, and the larva was observed 

 only in the bloom. 



Three wild malvaceous plants are rather common in the Laguna 

 district. These are SpJiaeralcea cuspidata (Gray) , Sida liederacea Torr. , 

 and Malva parviflora L. Quantities of these plants were collected 

 repeatedly and placed in rearing cages, but no stages of the pink 

 boUworm were ever found on them. In many cases these plants were 

 collected immediately adjoining cotton fields. Larvas of the lepidop- 

 teron Noctuelia rufofascialis Stephens were found in considerable num- 

 bers in the seed pocis of these plants. This larva attains practically 

 the same size as the pink bollworm and it is found occasionally feeding 

 on cotton, both in the blooms and in the bolls. The pods of these 

 malvaceous plants are large enough to enable the pink bollworm to 

 reach maturity in them. 



A few specimens of Hibiscus coulteri Harv. were found on the moun- 

 tains near Tlahuahlo, but they were not infested. 



RELATION OF ALTERNATIVE FOOD PLANTS OF THE PINK BOLLWORM TO NONCOTTON 



ZONES 



In the United States in the work of eradicating the pink boUworm 

 the planting of cotton over extensive areas has been prohibited. 

 This work appears to have been entirely successful in bringing about 



