﻿STUDIES OP THE PINK BOLLWORM IN MEXICO 



25 



In November and December of 1921, Schutz and Haskell of the 

 Bureau of Markets and Crop Estimates of the United States Depart- 

 ment of Agriculture made a survey of the Laguna district, to obtain 

 data on the economic phases of the pink boUworm situation. By the 

 use of questionnaires they obtained from plantation owners and 

 managers data on the average loss due to the pink bollworuli. From 

 a total of 143 estimates of the losses during the period ftom 1915 

 to 1921, inclusive, they obtained an average yearly loss rec/jrd of 23.4 

 per cent of the crop. Their averages were 22.4 per cer/t for 1921 

 and 30.4 per cent for 1920, based on 39 and 36 estimates, respectively. 



CONDITIONS AFFECTING DAMAGE 



SUMMER IRRIGATION 



Cotton in the Laguna district which receives summer irrigation is 

 usually more severely damaged by the pink bollworm than unirri- 

 gated cotton. The irrigation causes later fruiting, and this late crop 

 becomes subject to attack at the time of the season when the pink 

 bollworm is most abundant. Table 19 shows the progress of the 

 infestation in irrigated and unirrigated fields in both 1921 and 1922. 



Table 19. — Average number of worms -per green boll in irrigated and unirrigated 



fields 





1921 



Date 



1922 



Date 



Irrigated! 



Unirri- 

 gated 



Irrigated 



Unirri- 

 gated 



July 24 



0.33 

 .27 

 .43 

 1.22 

 1.81 

 2.81 

 4.37 

 3.92 

 5.37 

 6.36 



0.57 

 .45 

 .30 

 2.34 

 2.27 

 3.63 

 4.08 

 3.54 

 5.20 

 6.16 



June 27 



0.14 

 .18 

 .38 

 .36 

 .60 



1.85 



0.03 



Aug. 2 



July 8.... 



.02 



9. 



18 



.11 



16 



28 



.14 



23 



' Aug. 7. . 



.27 



30 



17- - 



.77 



Sept. 6. . 



27 



5.05 1 2.95 



13 



Sept. 5. 



6.87 

 2 8.32 

 2 5.50 



4.55 



20 



16 





27 



27. - 







Average 





Average.- 



2.69 



2.85 



1..93 



1.10 









1 Dates of irrigation: 1921, July 24; 1922, July 11. 



2 Not included in average. 



According to these records the unirrigated cotton in the first part 

 of the season of 1921 was a little more severely infested than the 

 irrigated, but the condition became reversed in the latter part of the 

 season, with a smaller percentage difference. In 1922 the irrigated 

 cotton showed a heavier infestation throughout the season. 



A few plantations in the Laguna have wells which supply summer 

 irrigation water. Their irrigation practices dift'cr from those on other 

 plantations in that less water is applied in the fall and winter flood- 

 ings and several irrigations are given during the summer. Planta- 

 tions Xos. 16 and 27 in Table 17 are irrigated in this manner. An 

 unusually low figure for the nonpickable cotton on plantation No. 27 

 is shown in 1921 and 1922. Iho figure for plantation No. 16 for 

 1922, however, is not unusually low. Possibly the low damage on 

 the former was due to early maturity of the crops as a whole caused 

 by timely irrigations, which prevented the usually very definite sepa- 

 ration between the first and second crops found in fields that receive 

 late irrigation of river water. 



G077G— 26t 1 



