Chemical weed control history

This book is about the revolutionary impact of the triazines herbicides, likely the most important class of agricultural chemicals ever developed. For five decades the triazines have provided weed control in more than 50 crops around the world and have helped farmers boost yields and produce enough food to feed a rising global population. The triazine herbicides, and especially atrazine, are the most well-researched herbicides in history, with thousands of scientific studies on their safety to humans and the environment. Data from studies on the triazines have been evaluated extensively by regulatory authorities around the globe to ensure their safe use. 

Between 1976 and 1978 Stauffer Chemical Company researchers identified fields where EPTC failed to give expected herbicidal activity. The fields had a history of repeated annual applications of EPTC. Greenhouse bioassays with EPTC demonstrated reduced persistence as the cause of reduced weed control observed in the field. Sterilization of the soil with heat or chemicals restored herbicidal activity. This indicated that, in some soils, enhanced microbial degradation might be associated with the observed reduction in herbicidal activity (D.L. Hyzak, personal communication). 

Reduced weed control with butylate in butylate history fields was reported in 1983 (7,8). Laboratory, greenhouse and field trials demonstrated that repeated annual use of butylate may cause enhanced butylate biodegradation and result in reduced weed control. Reports of reduced weed control with repeated use of butylate were much less frequent than with EPTC (Stauffer Chemical Company unpublished). Since 1986, the potential for enhanced biodegradation of butylate has been documented and described more completely by researchers in the Southeastern U.S. (9,10,11,12). 

Resistance. Pest resistance to chemical control has a long history, but currently its scope and speed of development are accelerating 1531 No class of compound is unaffected. A striking example is emergence of weeds resistant to sulfonylureas — and implementation of resistance management strategies involving mixtures and short-residual compounds — soon after their introduction (Brown and Kearney, this volume). 

The history of agricultural production has been inextricably lirtked to the control of weeds, pests and diseases in crop production practices. There is no doubt that the production of consistently high yielding, highqrrality crops requires the use of pesticides. Although orgarric production methods provide a viable alternative the yields achieved are lower arrd the qrrahty of the produce can be more variable. The aim, therefore, of an IFM system is to utilise the cultural control methods that are known to reduce the incidence of pests on crops, and then use crop protection chemicals as a final resort. 

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