PLANT RESPONSES TO INSECTICIDES IN THE SOIL 



25 



Table 7. — Effect of toxaphene in soil in the greenhouse on stand and growth 

 of seedlings within h months of application, Beltsville, Md., 191+7 



GERMINATION AND STAND 



Crop 



Duplicate 



tests 



Response to pounds per acre of toxaphene shown 







25 



100 



400 



1,0001 



L.S.D.2 



Sensitive plants: 



Bean, snap 



Pumpkin 



Squash, summer 



Number 

 2 

 1 

 2 

 1 

 1 

 1 



Percent 

 88 

 68 

 60 

 52 

 90 

 28 



Percent 



85 

 72 

 46 

 57 

 66 

 31 



Percent 



85 

 64 

 45 

 38 

 67 

 37 



Percent 

 71 

 57 

 45 

 29 

 48 

 7 



Percent 

 61 

 64 

 42 

 24 

 42 

 



Percent 

 ( 3 ) 

 (3) 

 (3) 

 ( 3 ) 



Tomato 



Watermelon 



40 

 13 







65 



60 



56 



43 



39 



12 









Less sensitive plant: 



1 



98 



94 



97 



94 



94 



( 3 ) 







WEIGHT PER PLANT 



Sensitive plants: 



Pumpkin 



Squash, summer 



Tomato 



Number 



1 

 2 

 1 

 1 



Grams 



24.7 



17.5 



4.7 



5.7 



12.9 



Grams 



16.9 



16.1 



5.5 



7,3 



11.5 



Grams 

 16.7 



7.7 

 4.5 

 3.1 

 8.0 



Grams 



15.1 



6.4 



2.2 



.9 



6.2 



Grams 



13.8 



3.4 



.8 



Grams 



6.7 



9.1 



.8 



2.9 







Less sensitive plants: 



Bean, snap 



Corn, sweet 



Squash, winter 



2 

 1 



1 



10.1 



7.2 



12.9 



10.7 



6.0 



11.8 



9.8 

 4.9 

 8.3 



10.1 



4.8 

 4.9 



9.3 

 3.3 



(3) 

 (3) 

 (3) 



Mean 





10.1 



9.5 



7.7 



6.6 



6.3 





1 The 1,000-pound treatment is not included in the variance analysis, bee 

 replication of treatment. 



2 Least significant difference at the 5-percent level. 



3 Differences among treatments not significant. 



ause there was no 



Results With Parathion 



Parathion (0,0-diethyl para-nitrophenyl thiophosphate) is a 

 compound of remarkable toxicity to insects and to man and ani- 

 mals. Its insecticidal properties persist for only a few days after 

 its has been sprayed or dusted onto crops, and it is now believed 

 to decompose into harmless products. In 1948, however, its amaz- 

 ing potency as an insecticide and the lack of definite information 

 about how it might behave in soil called for its inclusion in these 

 studies. 



Table 8 shows that amounts of parathion from 1.5 pounds up 

 to 100 pounds per acre had no consistent and significant harmful 

 effects on a wide range of vegetable crops, with the possible ex- 

 ception of snap beans and muskmelons. In a few instances, as 

 tomatoes and rye on the 50-pound plot, there appeared to be 

 significant increases above the control. Two such instances are 

 not surprising in a table of 88 items, considering that in a random 

 sample 2 items may be a little above and 2 a little below the "5- 

 percent level. ,, 



