COTTON IN WEEVIL-CONTROL EXPERIMENTS 8 
even when surface moisture becomes deficient. June was very dry, 
with only 0.55 inch of rain. Precipitation during the growing period 
of cotton was fairly well distributed, but effective rains fell on only 
six days between May 30 and September 7. 
Maximum temperatures during June, July, and August were 
comparatively high, and the long periods of hot weather between the 
few good rains resulted in droughty conditions in spite of the appar- 
ently adequate precipitation. 
The average monthly maximum and minimum temperatures and 
the monthly precipitation for the season of 1923 are given in Table 1. 
TABLE 1.—Average minimum and maximum temperatures and monthly preciptia- 
tion at San Antonio, Tex., from April to September, 1923 
Items of comparison Tau to Apr. May June July Aug. Sept. 
Average temperature (° F.): 
IVbsabrog rene Pel Re Se ee eee 59. 3 64.5 72.4 TA.2 72.4 70. 7 
IMA SITULIN Soe See ee a ee 77.6 89.0 95. 4 95. 3 97.8 89. 4 
Precipitation (inches): | 
1h payee see ee eee | 9.27 |" 2. 93 1. 67 OD Soul 2. 50 3. 02 
Average, 1907 to 1920 ____-___| 3. 98 3. 11 3. 09 1.88 2 1. 87 Paty | 
Favorable conditions for the hibernation of boll weevils in the San 
Antonio district are afforded by scattered areas of undeveloped land 
covered with mesquite and huisache trees and by large fields of 
Johnson grass. A heavy infestation from overwintered weevils 
usually occurs in cotton planted in this section. The first new genera- 
tion of weevils usually appears before the first of July. 
Periods of dry weather often restrict the growth of the plants, and 
the shed squares are exposed to direct sunlight, so that a natural 
control of the weevils may result from destruction of the larval and 
pupal stages in the fallen squares. When heavy rainfalls occur 
during the early stages of plant growth, excessive vegetative develop- 
ment of the plants results, so that the weevils have more protection 
even though there is dry weather later in the season. There is 
slight possibility of effective natural control when the plants grow 
large and the lanes between rows are shaded so as to protect the 
infested squares. 
In the season of 1923 weevils were first found on May 28. Squares 
were very small at that time, but by the first week in Junc numerous 
poe squares could be seen in all cotton which had reached the 
ruiting stage. Dry weather throughout the greater part of May 
and June retarded the growth of the plants. This small size kept 
the lanes open between the rows and afforded favorable conditions 
for natural control of weevils by exposing the fallen squares to direct 
sunlight. Nevertheless, the weevil infestation increased slowly, until 
by the first of August there were enough weevils to destroy practically 
all of the squares. 
COMPARISON OF SUCCESSIVE ADJACENT PLANTINGS AT SAN 
ANTONIO 
At San Antonio the successive plantings were made on April 19 
and 28 and May 5and12. The Lone Star variety was used, the seed 
having been grown on the experiment farm in 1922. The rows were 
