﻿STUDIES OP THE PIJSTK BOLLWORM IN MEXICO 



61 



Treatment of the cotton, particularly in the early plats, was 

 followed by aphid infestation, which reduced the yield considerably. 

 On this account the yields of the early-treated plats were for the 

 most part lower than those of the check plats. There was a slight 

 increase in yield" of the treated plats of the second group. 



Poisoning experiments were continued in 1922, but on a slightly 

 different basis. Instead of making applications of poison on all 

 plats till the end of the season, an equal number of treatments was 

 given each plat, but during different parts of the season. Most of 

 the plats were arranged in several six^-plat series with two check 

 plats to the series. Treatments on each series covered a period of 16 

 applications at five-day intervals. One such series then consisted of 

 the following: 



Plat 1, check. 



2, first 7 applications. 



3, applications Nos. 4 to 10, inclusive. 



4, applications Nos. 7 to 13, inclusive. 



5, applications Nos. 10 to 16, inclusive. 



6, check. 



Infestation records were kept on each plat throughout the season. 

 In addition to the use of calcium arsenate and arsenite of zinc in 

 different series, one entire series was treated with lead arsenate. 



Although a considerable volume of data was obtained in the 1922 

 experiments, no very definite conclusions could be drawn other than 

 those drawn from the 1921 experiments. The plats receiving the 

 early applications showed a greater percentage reduction in infesta- 

 tion during the period of treatment than later ones, amounting in 

 some individual examinations to more than 50 per cent. But after the 

 period of treatment the infestation rose again. The later applications 

 on the other hand caused a greater reduction in actual number of 

 worms per boll, and an average of all the examinations in each plat 

 showed a lower number of worms per boll in the later plats. This 

 point is illustrated in Table 49, in which are summarized data from 

 2 complete and 1 incomplete 6-plot series. 



Table 49. — Summary of Series D, E, and G, 1922 'poison tests 



Plat 

 No. 



Poison 

 applications 



Aver- 

 age 

 num- 

 ber of 

 worms 

 per boll 

 per ex- 

 amina- 

 tion 



Daily average 



number of 

 blooms per acre 



Bolls per plant 



Yield (pounds per 

 acre) 



Per- 

 cent- 

 age 



First 

 crop 



Second 

 crop 



First 

 pick- 

 ing 



Second 

 pick- 

 ing 



First 

 pick- 

 ing 



Second 

 pick- 

 ing 



Total 



non- 



pick- 



able 



cotton 



1 and 6.. 



2 



3 



None .... 



3.89 

 3.07 

 3.04 

 3.00 

 2.89 



6,211 

 6,676 



6, 087 

 0,341 

 6,128 



2,939 

 2,592 

 3,363 

 3, 302 

 3,154 



5.17 

 6.97 

 5.66 

 6.80 

 6.50 



2.22 

 2.02 

 2.54 



2.yi 



3.04 



1,062 

 1,275 

 1,172 

 1,074 

 1,076 



48 

 69 

 142 

 180 

 138 



1,110 

 1,344 

 1,314 

 1,260 

 1,214 



13.4 



First? 



10.6 



4 to 10, inclusive- - 

 7 to 13, inclusive.. 

 10 to 16, inclusive.. 



13.2 



4 



5 



11.5 

 13.3 



Aphid damage in 1922 was checked by dusting with nicotine 

 sulphate preparations. As many as three applications wore necessary 

 on some of the scries. Whenever an application on one plat became 

 necessary, all plats in the series were treated, checks included, so 

 that any action of the nicotine on the pink bollworm would be the 

 same for all plats. 



