PLANT RESPONSES TO INSECTICIDES IN THE SOIL 7 



of the seeds. Brooks and Anderson (7), however, found that 

 heavy coating with DDT and a "sticker" before planting reduced 

 germination and stand of lima bean about 40 percent and one 

 variety of sweet corn about 33 percent. 



Smith and Wenzel (4-0) and Wilson and Choudhri (.45) found 

 DDT to have very little, if any, significant effect on numbers of 

 soil micro-organisms or on nitrifying or ammonifying power of 

 the soil. 



Most workers found one or more species of plants to be injured 

 at one or more of soil dosages of DDT with which they worked. 



Chapman and Allen (8) noted retarded germination of corn, 

 beans, and cucumber at 6.25, 25, and 100 pounds per acre in 

 sawdust. Corn was later stimulated, but cucumbers were injured. 

 Goldsworthy and Dunegan (18) found progressive reduction in 

 number and weight of strawberry plants produced by mother 

 plants in soil with 12 up to 100 pounds of DDT per acre; p,p' 

 DDT was about one-third to one-fourth as toxic as technical 

 DDT (16). Young and Gill (47), using 10, 25, and 100 pounds 

 of DDT per acre, found rye, tomato, and strawberry most sensi- 

 tive, and collard, eggplant, and onion less so. Morrison and 

 others (32) reported bush and pole beans were seriously stunted 

 by 138 pounds per acre of DDT. Using no more than 25 pounds 

 of DDT per acre, Fleming (14) noted injury to strawberry, 

 tomato, lima bean, snap bean, onion, and spinach. Certain herba- 

 ceous ornamentals were injured, but when the 25 pounds of DDT 

 per acre was applied to the surface of soil in which woody peren- 

 nials were already well established, they were uninjured. Many 

 vegetables also were uninjured by 25 pounds. Roberts (38) in- 

 jured germination of corn and cotton by adding 0.1 gram of DDT 

 per 8-inch pot of soil before planting. 



Goldsworthy (17) observed progressive reduced growth of 

 1-year-old peach trees in sand culture containing from 25 to 

 1,000 pounds of DDT per acre, but in soil 200 pounds or more 

 was required to retard growth significantly. Kulash (26) stated 

 that 200 and 400 pounds per acre retarded germination and early 

 growth of corn. Allen and others (3) observed no significant 

 effect of DDT up to 100 pounds per acre on tobacco, cotton, or 

 cowpeas, but rye was seriously reduced in yield by 40 and 100 

 pounds. 



Investigators who found no injury or other pronounced plant 

 response to the amounts of DDT used in their respective studies 

 are listed in the following two paragraphs, together with brief 

 notations on the nature or conditions of their work. 



Wilson and Choudhri (45) conducted a small laboratory test, 

 using tumblers of treated soil containing 250 to 10,000 pounds 

 of DDT per acre to grow plants for 35 days during midwinter 

 with the aid of artificial light. No effect of DDT was noted on 

 alfalfa, red clover, soybean, or vetch. 



Lane and others (28), Kulash (27), and Riherd (37), working 

 with various amounts of DDT per acre in the soil, found no 

 injury to corn up to 10 pounds, to lima beans up to 20 pounds, 

 and to potatoes up to 40 pounds. Lhoste and Ravault (29) found 

 no effect on wheat up to 300 kilograms per hectare. Grayson 



