STUDIES OF THE PINK 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 poisqn 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, 
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 
1 
Second j 
pick- Total 
ing 
non- 
pick- 
able 
cotton 
1 and 6_. 
None 
3.89 
3.07 
3.04 
3.00 
2.89 
6,211 
6,676 
6,687 
6,341 
6,128 
2,939 
2,592 
3,363 
3,302 
3,154 
5.17 
5.97 
5.56 
5.80 
5.50 
2.22 
2.02 
2.54 
2.91 
3.04 
1,062 
1,275 
1,172 
1,074 
1,076 
48 
69 
142 
186 
138 
1,110 
1,344 
1,314 
1,260 
1,214 
13.4 
2 
First 7 
10.6 
3 
4 
5 
4 to 10, inclusive.. 
7 to 13, inclusive. _ 
10 to 16, inclusive. . 
13.2 
11.5 
13.3 
Aphid damage in 1922 was checked by dusting with nicotine 
sulphate preparations. As many as three applications were necessary 
on some of the series. 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. 
