BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 69 
to 2) applied at the rate of 12 pounds per acre was 212 pounds per 
acre, or the same as from calcium arsenate, undiluted, applied at the 
rate of 4 to 6 pounds per acre; on late-planted cotton in which boll 
weevils were abundant and the rapid and tarnished plant bugs fairly 
abundant, sulfur dust alone was responsible for an increase of 105 
pounds of seed cotton per acre; calcium arsenate-sulfur (1 to 1) for 
488 pounds, and calcium arsenate, undiluted, for 438 pounds. 
At College Station, Tex., with a light boll weevil and light flea 
hopper infestation, the use of calcium arsenate-sulfur mixtures (1 to 
1 and 1 to 2) resulted in gains of 337 pounds of seed cotton per acre, 
and the use of calcium arsenate, undiluted, in 379 pounds. 
Cage tests for the control of the boll weevil in which calcium arsen- 
ates containing low, intermediate, and high percentages of water- 
soluble arsenic pentoxide as determined by the New York method were 
continued, the average net mortalities for the 2 years being 60 per- 
cent with the low (0.4 percent), 78 percent with the intermediate (4.5 
percent), and 76 percent with the high (10.5 percent). A cooperative 
field test of these high, intermediate, and low calcium arsenates was 
made at six stations of the Division and at the Texas Agricultural 
Experiment Station. In all, 8 tests, consisting of a total of 45 replica- 
tions for each treatment, representing different climatic and boll 
weevil conditions, were made. Randomized-block plot arrangements 
were used, the plots being one-thirtieth of an acre in area. Statisti- 
cally, the square infestations and yields did not differ in the plots 
receiving calcium arsenates containing low, intermediate, and high 
percentages of water-soluble arsenic pentoxide. However, both high 
and intermediate calcium arsenates appeared to be slightly more toxic 
to the weevils in cage tests, whereas in field tests the yields in plots 
dusted with the low were slightly better. Since the results obtained 
in the field plots are not in accord with those of the cage tests, the tests 
are being repeated this year in an attempt to find which type of 
calcium arsenate is best under field conditions. 
The addition of several wetting agents to calcium arsenate and 
cryolite dusts did not significantly affect the insect mortality in cage 
tests. Dicalcium arsenate caused a significantly higher boll weevil 
mortality in cage tests than did tricalcium arsenate and commercial 
calcium arsenate. 
In field tests with cryolite conducted at Florence, Tallulah, and 
College Station much better control was secured than last year, and 
material containing a high percentage of sodium fluoaluminate was 
more effective than that used previously. The physical qualities of the 
cryolites ;ue very poor for dusting. 
Continued experiments on boll weevil control on sea-island cotton 
at Tifton, Ga., and Gainesville, Fla., where the infestations were 
heavy in 1938, again demonstrated that adequate protection against 
the late-season migratory weevils constitutes the crucial problem in 
control on long-staple cotton. At Gainesville the best control un- 
secured by using a spray of calcium arsenate (10 pounds to 50 gallons 
of water) applied with small compressed-air sprayers at the rate of 
20 to 30 gallons per acre. The yield was increased 127 percenl . The 
second-best gain was obtained with calcium arsenate dust — 119 per- 
cent over the checks. At Tifton spraying with 5 pounds of calcium 
arsenate to 1 gallon of cane syrup and 49 gallons of water gave good 
