Carbofuran degradation

Effect of pH, soil type, and application rate on carbofuran degradation in soils... 

Pharmacologically, carbofuran inhibits cholinesterase, resulting in stimulation of the central, parasympathetic, and somatic motor systems. Sensitive biochemical tests have been developed to measure cholinesterase inhibition in avian and mammalian brain and plasma samples and are useful in the forensic assessment of carbamate exposure in human and wildlife pesticide incidents (Bal-lantyne and Marrs Hunt and Hooper 1993). Acute toxic clinical effects resulting from carbofuran exposure in animals and humans appear to be completely reversible and have been successfully treated with atropine sulfate. However, treatment should occur as soon as possible after exposure because acute carbofuran toxicosis can be fatal younger age groups of various species are more susceptible than adults (Finlayson et al. 1979). Carbofuran labels indicate that application is forbidden to streams, lakes, or ponds. In addition, manufacturers have stated that carbofuran is poisonous if swallowed, inhaled, or absorbed through the skin. Users are cautioned not to breathe carbofuran dust, fumes, or spray mist and treated areas should be avoided for at least 2 days (Anonymous 1971). Three points are emphasized at this juncture. First, some carbofuran degradation... 

Table 12.2 Effect of pH, Soil Type, and Application Rate on Carbofuran Degradation in Soils... 

Sterilized soils did not show evidence of carbofuran degradation (Felsot et al. 1981)... 

In a small watershed, carbofuran was applied to corn seed farrows at a rate of 5.03 kg/ha active ingredient. Carbofuran was stable up to 166 d, but after 135 d, 95% had disappeared. The long lag time suggests that carbofuran degradation was primarily due to microbial degradation (Caro et al., 1974). 

Ramanand, K., Panda, S., Sharmila, M., Adhya, T.K., and Sethunathan, N. Development and acclimatization of carbofuran-degrading soil enrichment cultures at different temperatures, J. Agric. Food Chem., 36(l) 200-205, 1988. 

Research on control failures during the late 1970 s and early 1980 s focused on carbofuran, a compound that had earlier provided excellent control and had captured a considerable share of the rootworm insecticide market (e.g. 20% of treated acres in Iowa in 1977)(9). Although some studies found no correlation between prior use of carbofuran and an enhanced rate of carbofuran degradation (10.11) both monitoring of field residues (12-14) and laboratory degradation tests (15-17) conclusively demonstrated enhanced microbial degradation as the cause of decreased carbofuran persistence in fields with histories of carbofuran use. Thus, a... 

We are developing an understanding of how microbial populations in enhanced soils respond to carbofuran. Our efforts have centered around two sets of soils in which enhanced carbofuran degradation has been demonstrated (5). We have estimated the microbial population changes in these two systems. 

Of the three insecticides studied, enhanced biodegradation has been definitively associated with repeated applications of carbofuran ( ). In our studies, the chemical assay data from 1987 only weakly suggested the development of enhanced biodegradation, and the data from 1988 indicated that biodegradation rate was not affected by multi-year carbofuran treatments. Since a severe drought occurred in 1988, a lack of soil moisture may have slowed the rate of carbofuran degradation. 

Table IV. Carbofuran Degradation and Carbofuran Phenol Production in Liquid Suspensions Inoculated with Enhanced and Non-enhanced Soil...

Carbofuran degrades slowly in neutral or acid aerobic soils with half-lives that may range from 1-8 weeks. 

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