BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 15 
to the soil it was taken up by the plants and killed aphids and mites 
feeding on them. 
Parathion Effective Against Green Peach Aphid on Tobacco 
The green peach aphid continues to cause grave concern to tobacco 
growers. Light but widespread infestations were reported from North 
and South Carolina, Georgia, and Florida in April 1949. In North 
Carolina they remained light to moderate, but in the other three States 
by the last of June the pests had built up to the highest populations 
since 1946, when they first appeared on tobacco. Infestations were 
reported from Maryland, Virginia, and Tennessee in May, and from 
Connecticut in June. 
In experiments during the past year progress was made toward 
finding a suitable method of control on shade-grown tobacco in Flor- 
ida. Encouraging results were obtained with dusts containing 1 per- 
cent of parathion. No injury to the plants was evident. A dust con- 
taining 1 percent of the essentially pure gamma benzene hexachloride 
was fairly effective against light infestations, although less so than 
parathion, but technical benzene hexachloride was found to injure 
the tobacco plants. Promising results were also obtained with sprays 
containing 1 pint of 10-percent tetraethyl pyrophosphate in 100 gal- 
lons of water. The addition of a 10-percent DDT dust to the para- 
thion provided protection against associated infestations of horn- 
worms, budworms, and garden fleahoppers in one treatment. 
In Florida the destruction of the favorite host plants, such as col- 
lards and several species of weeds, in and around fields where shade 
tobacco was grown aided materially in controlling the aphids. 
Effect of Insecticides on the Yield and Quality of Tobacco Tested 
The effect of mixing DDT, benzene hexachloride, and toxaphene in 
the soil on the yield and quality of tobacco grown therein was studied 
at Florence, S. C, in cooperation with the Bureau of Plant Industry, 
Soils, and Agricultural Engineering and the South Carolina Agricul- 
tural Experiment Station. DDT in dosages up to 40 pounds per acre 
had no adverse effect on the tobacco ; an excessive dosage of 100 pounds 
per acre tended to impart a slightly abnormal sweet taste to the cured 
product but did not affect the yield. Technical benzene hexachloride 
in dosages as low as 2 pounds of the gamma isomer per acre gave an 
off-taste, and excessive dosages ranging from 6 to 10 pounds of gamma 
per acre reduced the yield slightly as well as the quality. Toxaphene 
at 20 pounds per acre slightly retarded the growth of tobacco plants 
and reduced the yield. 
The effect of foliage applications of various insecticides on the taste 
and aroma of the tobacco was studied in cooperation with the tobacco 
industry. The tests were made by tobacco experts, or specialists in 
judging various aspects of' tobacco quality. The insecticides used 
were DDT, benzene hexachloride, toxaphene, parathion, and tetraethyl 
pyrophosphate. Technical benzene hexachloride was the only mate- 
rial that showed any consistent evidence of deleterious effect on the 
