Enhanced degradation discovery

Field studies with single applications of phenoxyalkanoic acid herbicides have indicated that breakdown is rapid under temperature and moisture conditions that favour microbiological activity (5). Enhanced degradation of these herbicides, under field conditions, was first noted in the late 1940s. The use of plant bioassay procedures, led to the discovery that the persistence of 2,4-D, but not 2,4,5-T, was decreased,by pretreatment of the soil with 2,4-D (26, 27). This enhanced breakdown was later confirmed using (14C)2,4-D and radiochemical analytical techniques (29). The breakdown of the (14C)2,4-D being more rapid in soil from the treated plots, tested 8 months after the last field application, than in soil from plots treated for the first time. 

Carvone is a chemical component of the spearmint plant that has been shown to enhance the growth and ability of Arthrobacter bacteria to degrade polychlorinated biphenyl (PCB). Until this discovery the only known method of strmnlating the bioremediation of PCBs was addition of biphenyl to the soil however, biphenyl is itself a toxic snbstance. 

The discovery that crop tolerance for a particular herbicide could be enhanced has led to the identification of many compounds that antidote the herbicidal effect of the thiolcarbamate herbicides. iV,A/ -Diallyl-dichloroacetamide was the first material commercialized with thiocarbamate herbicides for use in corn. This same concept also has application for other types of herbicides. Also it was discovered that repeated application of the same thiolcarbamate led to rapid microbial degradation of the material in the soil. Addition of extenders to the thiolcarbamate herbicide counteracted with degrading effect of the microorganisms in the treated soil. 

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