Enhanced biodegradation of carbamothioate

Enhanced Biodegradation of Carbamothioate Herbicides in South Carolina... 

Based on field and laboratory data, enhanced biodegradation of carbamothioate herbicides was confirmed under South Carolina conditions. A good correlation was observed between enhanced biodegradation and performance failure. Laboratory analyses of "problem" soils could be used to predict potential problems or weak efficacy under field situations. However, lack of soil... 

Data presented do not directly address enhanced biodegradation of carbamothioate herbicides other than EPTC. However, research indicates that both dietholate and SC-0058 reduce enhanced butylate biodegradation problems (Harvey, R. G. Weed Sci.. in press). 

Enhanced biodegradation of pesticides has received considerable attention in recent years since it was first described by Audus (1) for the herbicide 2,4-D. Diphenamid, a soil applied herbicide, is also subject to enhanced biodegradation by soil microorganisms (2.31. Fungicides (4.51 and insecticides (6-91 are also subject to enhanced degradation by soil microorganisms. The carbamothioate herbicides are readily degraded by microbes (10.Ill and especially after repeated applications (12-191. ... 

Continuous use of cycloate plus cyanazine over the six-year period provided an average of 89% millet control even though cycloate is a carbamothioate herbicide (Table IV). Previous studies have shown little potential for enhanced biodegradation of cycloate (8). Alachlor plus cyanazine or pendimethalin plus cyanazine treatments, often considered as alternatives to EPTC for millet control, did not provide better millet control than combinations of cyanazine plus EPTC or EPTC plus dietholate when the latter treatments were used no more frequently than every other year. 

Roeth FW, Wilson RG, Martin AR, Shea PJ (1990) Enhanced carbamothioate herbicide degradation research in Nebraska. In Racke AD, Coats JR (eds) Enhanced Biodegradation of Pesticides in the Environment. American Chemical Society, Washington DC, pp 23-36... 

This paper reviews the results of previously unpublished trials conducted by Stauffer Chemical Company and ICI Americas Inc. on the effects of cultural and chemical practices on the activity of carbamothioate herbicides in soils. The inter-relationship of these factors in the expression of enhanced biodegradation and the commercial significance and management of enhanced biodegradation in the cases of the carbamothioate herbicides EPTC, EPTC + dietholate, and butylate is demonstrated. 

Other factors besides enhanced biodegradation which influence carbamothioate herbicide persistence include environmental conditions, application efficiency, soil incorporation, crop and chemical rotation, herbicide combinations, and chemical extenders (4-6,12-13,17,20). Lack of commercially acceptable weed control may be attributed to misapplication, poor soil preparation and incorporation, and high weed populations, as well as enhanced biodegradation. 

Apparent Elimination of Enhanced Biodegradation. Good farming practices and favorable environmental conditions may maximize the efficacy of carbamothioates and provide acceptable weed control... 

The increased weed control in carbamothioate + atrazine or metolachlor tank mixtures may be due to the 1) additive/synergistic action of the tank mix 2) inhibition of enhanced biodegradation, or 3) activity of atrazine as a mild extender for carbamothioate herbicides. 

Tank mixtures of carbamothioates with atrazine or metolachlor reduced the expression of enhanced biodegradation (Tables V-VI). Other rotations of crops and or chemical classes can achieve the same results (4). 

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