Pesticide market structure

The need to develop and use chiral chromatographic techniques to resolve racemates in pesticide residues will be driven by new hazard and risk assessments undertaken using data from differential metabolism studies. The molecular structures of many pesticides incorporate chiral centers and, in some cases, the activity differs between enantiomers. Consequently, in recent years manufacturers have introduced resolved enantiomers to provide pesticides of higher activity per unit mass applied. For example, the fungicide metalaxyl is a racemic mix of R- and 5-enantiomers, both having the same mode of action but differing considerably in effectiveness. The -enantiomer is the most effective and is marketed as a separate product metalaxyl-M. In future, it will not be satisfactory to rely on hazard/risk assessments based on data from metabolism studies of racemic mixes. The metabolism studies will need to be undertaken on one, or more, of the resolved enantiomers. 

To produce QSAR models, a data set containing chemicals within a specified well-defined end-point is necessary. Since our knowledge about the properties of the natural compounds that surround us is very poor, especially for allelochemicals and toxicological evaluation of synthetic pesticides is well documented (regulators oblige the chemical industry to produce experimental data for synthetic chemicals, before they can be marketed), when allelochemicals toxicity values are not available, pesticides with similar structure can be used in the analysis. Therefore suitable data sets can be defined with pesticides and their activities, to predict the toxicity (activity) of the allelochemicals. 

A number of natural biopolymers containing pesticide active groups have been in the market for the purpose of developing ideal controlled release formulations for fungicides and herbicides. These biopolymers have been derived by natural exudation. Several factors appear to be important in governing the rates of release of active moieties. These factors include environmental conditions as well as the effects of the biopolymers compositions, properties and chemical structures, and the simulated conditions necessary to prolong the activity under suboptimal conditions such as the pH and temperature. 

Brazil accounts for 55% of pesticide sales in Central and South America. Pesticide sales in Brazil were US 1.4 billion in 1994 and an increase in sales was seen for all leading crops between 1993 and 1994 (up 57% for cotton, 44.8% for coffee, 36.3% for maize, 30.2% for soybean, 17.7% for citrus fruits and 11.5% for sugai cane). Herbicide sales dominate the market (50% in 1994) and it was predicted that usage would continue to expand as more farms convert to minimum tillage practices (due to severe problems with soil erosion and deterioration in soil structure) that rely on increased herbicide applications to control weeds,... 

It is estimated that 45-50 billion mosquito coils are used annually by approximately 2 billion people worldwide, mainly in Southeast Asia, but with a growing market in South America and Africa. Mosquito coils were traditionally made with finely groundpyrethrum daisy Chtysanthemum cinerariaefolium) flowers mixed with coconut husks or sawdust. Synthetic pyrethroids, based on the molecular structure of the pyrethrins contained in the pyrethrum daisy, have outstripped natural pyrethrins for use in household pesticides because they are far more photo stable, although both chemical groups possess rapid insecticidal and repellent action. Nonetheless, 17,000 tons of natural pyrethrum are produced in Kenya, Tanzania, Rwanda, and Australia annually to supply the household insecticide market. There is ample evidence that mosquito coils made from both natural pyrethrins and synthetic pyrethroids effectively repel mosquitoes. ... 

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