10 CIRCULAR 862, U. S. DEPARTMENT OF AGRICULTURE 



dragon, which were injured at 5 pounds, and pinks at 20 pounds. 

 The 10-pound treatment had lost no insecticidal value in 1 year, 

 but the 5-pound treatment began to lose at 10 months. Stitt and 

 Evanson (42) reported that 35 pounds per acre of chlordane 

 reduced stands of cucumbers, beans, beets, chard, and turnip, 

 while 5 pounds was without effect. 



Goldsworthy and Wilson (19) found that parathion from 6 to 

 100 pounds per acre progressively stimulated growth of straw- 

 berries. 



Kulash (27) recorded no effect on corn of 4 pounds per acre 

 of chlordane, 1 or 2 pounds of parathion, or 10 pounds of toxa- 

 phene. 



Goldsworthy (16) noted no harmful effect of toxaphene or of 

 chlordane, from 12 to 400 pounds per acre, upon strawberries. 



GREENHOUSE EXPERIMENTS 



Materials and Methods 



Unless otherwise specified the DDT used in the earlier years 

 of this work was of the technical grades as manufactured and 

 supplied by the Geigy Co., Inc., and the E. I. Du Pont de Nemours 

 & Co., Inc., in late 1945. It contained approximated 75 percent 

 p,p' DDT, 20 percent o,p' DDT, 5 percent p,p' TDE, 0.05 percent 

 bis(p-chlorophenyl) sulfone, and trace amounts of other closely 

 related chemicals. Preparations of later manufacture have since 

 been used that are higher in content of p,p' DDT and less toxic 

 to most plants than the material received in 1945. The highly 

 purified isomers and the isolated impurities, bis(p-chlorophenyl) 

 sulfone and p,p' TDE, were furnished by the courtesy of Drs. 

 H. L. Haller and R. C. Roark, of the Bureau of Entomology and 

 Plant Quarantine; Grasselli Chemicals Department, E. I. Du Pont 

 de Nemours & Co., Inc., and Hercules Powder Co., Wilmington, 

 Del. ; and the Geigy Co., Inc., New York. 



The technical BHC contained approximately 12 percent of the 

 gamma isomer and was obtained from Hooker Electro Chemical 

 Co. in 1946. The other substances on which data are presented 

 were obtained in the year indicated from the respective firms that 

 originated them: Chlordane from the Velsicol Corp. in 1946 and 

 Julius Hyman & Co. in 1948; toxaphene from Hercules Powder 

 Co. in 1946 ; and parathion from American Cyanamide Co. in 

 1948. 



Except for minor variations the several greenhouse studies 

 (fig. 1) on DDT were conducted as outlined briefly in the follow- 

 ing paragraphs. 



Repeated tests were run on four different soils, Chester loam, 

 Sassafras sandy loam, Evesboro loamy sand, and a New Jersey 

 muck. Each soil completely filled to a depth of 6 inches one or 

 more benches approximately 4 feet wide and 30 feet long. The 

 benches were divided crosswise by wooden partitions into nine 

 plots of equal size of which one received no DDT and the other 

 eight received DDT at the rates of 25, 100, 400, and 1,000 pounds 

 per acre in duplicate. Treatments were randomized within 

 benches, and soils were randomized among benches in each of two 



