BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 75 
COTTON INSECT INVESTIGATIONS 
BOLL WEEVIL 
The damage by the boll weevil in 1939 was similar in amount and 
geographical distribution to that of 1938. The severe damage re- 
ported last year along the Atlantic seaboard continued in Virginia, 
North Carolina. Georgia, and Florida, and extended into parts of 
Alabama and Mississippi in 1939. The average loss was estimated 
at 32 percent in Virginia, the highest ever recorded from that State, 
and at 23 percent in North Carolina, or slightly less than in 1938. 
In South Carolina the hot, dry growing season was very unfavorable 
for weevil development and reduced the damage for the State to 8 
percent, or only one-half of that of the previous year. The damage 
was also below average in all the States west of the Mississippi River 
where deficiencies in rainfall prevailed. The average reduction from 
full yield caused by the boll weevil for the United States in 1939 
was estimated at 8.7 percent, or 1.2 percent less than in 1938 and 
slightly below the 10-year average. 
The general conditions of weevil abundance and damage in rep- 
resentative sections are also shown by the gains secured from control 
measures. The increase in }'ields secured from treating plots in dif- 
ferent sections with the standard calcium arsenate dust after 10 
percent of the squares became infested is becoming of more value as 
an index of weevil damage as the records are accumulated over a 
period of years. At Florence, S. C, the average gain in 1939 was 
315 pounds of seed cotton per acre; at State College, Miss., 661 
pounds; at TaiTalah, La., 221 pounds as compared with a 20-year 
average of 305 pounds ; and at Waco, Tex., only 31 pounds per acre. 
Light defoliations by leaf worms allowed the weevils to continue 
developing late into the season and above normal numbers to enter 
hibernation in the fall of 1939. At Tallulah, La., 189 live weevils 
per ton of Spanish moss were found as compared with an average 
of 54 during the previous 4 } T ears. The expected heavy carry-over 
of weevils into 1940 was fortunately changed by the unusually low 
temperatures during January. At Tallulah there were freezing tem- 
peratures for 20 successive days and a minimum of —8° F. was the 
coldest ever recorded at that station, and practically all weevils hiber- 
nating in Spanish moss, cornstalks, and similar open shelter were 
destroyed. The emergence in hibernation cages with Spanish moss 
and cornstalk shelter was only 0.01 percent, the lowest ever recorded. 
No live weevils were found in the spring examination of Spanish 
moss collected from woods near cotton fields in several sections of 
the State. At Florence, S. C, with a minimum temperature of 
13° F., the survival was 0.08 percent. Lower temperatures and sur- 
vival occurred at Florence in 1936. The survival in cages at Lees- 
burg. Fla., was 11 percent, and at Waco, Tex., 0.09 percent. Previous 
records are not available for comparison at the latter places. How- 
ever, weevils hibernating in surface trash were protected from the 
cold by a heavy covering of snow over a large part of the Cotton Belt, 
and examinations of woods trash from near cotton fields snowed 
that weevils had survived in protected places. Trash examination 
at Tallulah showed an average of 2,243 weevils per acre last fall and 
190 in the spring of 1940, or a survival of 8.5 percent as compared 
