DISCUSSION 



During the period from 1957 through 1964, approximately 500 samples of 

 forage crops were analyzed for insecticide residues. The major portion of 

 these samples consisted of irange girass experimentally treated for grasshopper 

 control. Samples of red clover treated for root borer control and of lima 

 bean stiraw treated for control of certain foliage-feeding insects were also 

 analyzed. The presence of certain insecticide residues on the above-mentioned 

 forage could result in the deposition of these materials in the fat of the 

 animals and the possible secretion of the pesticides, or their metabolites, in 

 the milk. In results of analyses employing older procedures (prior to gas 

 chromatography and more sensitive colorimetric methods) , the lower level of 

 accuracy of the analytical method is presented where the residue levels found 

 were equal to or less than the lower limit. 



Red Clover 



Table 2 presents the residue levels found when red clover was treated 

 with one carbamate and three chlorinated hydrocarbon insecticides. Where 0.8 

 to 2.7 lb. of aldrin were applied, either as a granular material or as a dust 

 66 to 83 days before harvest, no measurable residues of aldrin or its metabo- 

 lite dieldrin vi^ere found on the red clover when the samples were analyzed by 

 colorimetric methods. When carbaryl was applied as a dust at 1.5 lb. per acre 

 49 days before harvest, the residue ranged from 0.20 to 0.47 p. p.m. Residues 

 on the same plots were less than 0.10 p. p.m. 65 days after application. 



The application of heptachlor either as the granular material or as a 

 dust resulted in measurable deposits of heptachlor and its metabolite, hepta- 

 chlor epoxide, when detennined by gas chiroraatography. No deposits in excess 

 of the lower limit of accuracy of the analytical methods were found by colori- 

 metric analysis. Red clover samples taken 51 days after treatment with either 

 0.25 or 1.00 lb. of heptachlor per acre, as granules, did not contain measur- 

 able deposits when analyzed by colorimetric methods. When 0.75 lb. of granu- 

 lar heptachlor was applied, residues of 0.14 and 0.01 p. p.m. of heptachlor and 

 heptachlor epoxide were found 201 days after application, because of the 

 increased sensitivity of the newer gas chromatographic methods of analysis. 



The aerial application of heptachlor granules at 1.3 lb. per acre 

 resulted in residues of 0.016 p. p.m. heptachlor and 0,004 p. p.m. heptachlor 

 epoxide 236 days after application, when analyzed by gas chromatographic tech- 

 niques. When 1.5 lb. of heptachlor, as granules, were applied by aircraft and 

 samples taken 77 days after application, no measui^ble residues were found by 

 colorimetric techniques. When the same amount was applied by aircraft as a 

 dust and sampled at 77 days after application, residues of 0.18 p. p.m. of 

 heptachlor were found by colorimetric methods. No measurable epoxide was 

 found. The increase in heptachlor residue is possibly explained by the nature 

 of the formulation applied. The granular material tends to scatter through 

 the foliage while the dust formulation adheres to the foliage. The presence 

 of residues of heptachlor or heptachlor epoxide at harvesttime prohibits 

 application of the rates and formulations tested where the foirage may be con- 

 sumed by lactating animals or animals being finished for slaughter. The 

 significance of the lower level deposits, such as 0.004 p,p,m., has not been 

 evaluated. 



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