BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 17 
Insecticides Field-Evaluated Against Boll Weevil 
Large-scale field experiments and small field-plot tests were con- 
ducted at Waco, San Benito, and Brownsville, Tex., Tallulah, La., 
Stoneville, Miss., and Florence, S. C, to evaluate several new insec- 
ticides and combinations of insecticides against the boll weevil and 
other cotton pests. 
In the Lower Rio Grande Valley, where boll weevil damage was 
greatest, dieldrin gave longer residual control of the boll weevil than 
any of the other insecticides tested. A combination of dieldrin and 
DDT applied at the rate of 0.25 to 0.375 pound of dieldrin plus 1 to 
1.5 pounds of DDT per acre controlled most of the major cotton in- 
sects. This combination, however, did not prevent a buildup of aphids 
and spider mites. 
Methyl parathion appeared promising for boll weevil, cotton aphid, 
spider mite, and cotton leafworm control. A combination of methyl 
parathion and DDT at the rate of 0.15 to 0.375 pound of methyl para- 
thion plus 0.5 to 1.5 pounds of DDT per acre was effective against all 
cotton pests. During heavy boll weevil migration, however, this com- 
bination was not so effective as the dieldrin-DDT combination, owing 
to lack of residual action of methyl parathion against the boll weevil. 
Endrin applied as a spray at the rate of 0.2 to 0.5 pound per acre 
appeared promising against the boll weevil, bollworm, and several 
other cotton insects. It was not effective against the pink bollworm, 
aphids, or spider mites. 
Isodrin at the rate of 0.2 pound per acre gave effective boll weevil 
control in tests conducted in South Carolina. 
EPN alone gave variable results against the boll weevil, but at 
Brownsville, Tex., a combination of EPN and DDT at the rate of 
0.5 pound of EPN to 1.5 pounds of DDT per acre appeared promising 
for the control of the boll weevil, bollworm, pink bollworm, spider 
mites, and several other cotton insects. This combination appeared 
weak against the cotton aphid, however. 
The following insecticides applied as dusts gave satisfactory con- 
trol of the boll weevil and a number of other insects : BHC containing 
3 percent of gamma plus DDT 5 percent; calcium arsenate applied 
alternately with BHC containing 3 percent of gamma plus DDT 
5 percent; lime-free calcium arsenate containing 1 percent of para- 
thion; aldrin 1.5 to 2.5 percent plus DDT 5 percent; dieldrin 1.5 to 
2.5 percent plus DDT 5 percent; and toxaphene 20 percent. Forty 
percent of sulfur was added to the organic mixtures to suppress spider 
mite buildup. 
Four sprays made from emulsion concentrates gave satisfactory 
control of the boll weevil and several other cotton insects. These, in 
per-acre dosages, were : 2 pounds of technical toxaphene plus 1 pound 
of DDT ; BHC at 0.3 pound of the gamma isomer plus 0.5 pound of 
DDT; 0.25 pound of aldrin plus 0.5 pound of DDT; and 0.15 pound 
of dieldrin plus 0.5 pound of DDT. 
Satisfactory Bollworm Control Obtained With Several Sprays 
Endrin was the only new insecticide tested that showed promise in 
controlling bollworms. It was ineffective in some tests as a dust. 
When applied in a spray at the rate of 0.2 to 0.25 pound per acre, 
