16 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE, 1953 
winter and the damage caused by this insect in L952 was extremely 
heavy. 
Spray Combinations Effective Against Many Cotton Insects 
Large-scale spray tests in the Lower Rio Grande Valley in 195-2 
indicate that spray combinations of DDT with either methyl para- 
thiol) or Metacide may control the pink bollworm, boll weevil, cotton 
aphid, bollworm, cotton leafworm, and spider mites. Average 
cotton yields from test fields -prayed with these combinations were 
almost three times the yield from untreated test area-. In one Held 
sprayed with DDT and methyl parathion combined, a gain of 1,600 
pounds of seed cotton per acre was obtained over the untreated area. 
All tests were in cooperation with the Texas Agricultural Experiment 
Station. 
Spray applications were begun on April 15. when about 10 percent 
of the blooms were infested with the pink bollworm, and repeated 
about once a week until July 3. The number of applications varied 
from 11 in one of the fields to 3 in another, and averaged a little 
more than 6 per field, which was below the average for applications 
of other sprays on many farms where the pink bollworm was a prob- 
lem in L952. The percentage of bolls infested by the pink bollworm 
averaged 61.2 in the untreated areas. L5.7 in areas sprayed with the 
DDT-methyl parathion combination, and L4.9 in areas sprayed with 
DDT plus Metacide. The methyl parathion-DDT combination held 
the boll infestation in another test to 9 percent while that of the 
corresponding check area averaged 63.1 percent. 
Dieldrin was added to the other materials in some of the final appli- 
cat ion- to provide better control of the heavy, late-season migration of 
t he boll weevil. Met hyl parathion in combinat ion with DDT appeared 
slightly more effective against the boll weevil than the Metacide-DDT 
combination. 
Search On for New Chemicals To Control Cotton Insects 
Endrin and the diethyl analog of mcthoxychlor. known as Q 128, 
were the only new chlorinated hydroca rhon insecticides tested which 
showed promise for control of the boll weevil. In Laboratory and 
field cage tests designed to discover new chemicals that may be 
useful in the control of spider mites and insects attacking cotton, these 
compounds appeared outstandingly effective at dosages of 0.25 and 
2.0 pound- per acre, respectively. This work, conducted at College 
Stat ion, Tex., was in cooperat ion with the Texas Agricultural Experi- 
ment Stat ion and \ arious insecticide and chemical manufacturers. 
Of the new phosphorus compounds, met hyl parathion at dosages o{ 
from 0.25 to 0.5 pound per acre appeared promising. EPN and l- 
methylumbelliferone 0,0-diethyl thiophosphate and their methyl 
analogs showed enough promise t<» justify further field testing. 
Chlorothion, a compound related t<> parathion, containing chlorine, 
also appeared promising at about >>..'» pound per acre. When nine 
homologous pair- of phosphorous compounds were tested against the 
boll weevil, the methyl homolog was in general considerably more 
effective than it< ethyl counterpart. Several compounds have been 
found in have 3vstemic activity against the boll weevil. 
