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Bt-toxin is not effective anymore in controlling cotton pink bollworm in the major cotton producing countries of South Asia. The cultivation of Bt-cotton without the use of 5% non-Bt plants as a refuge crop has made pink bollworm resistant to this toxin. On the other hand this pest has been successfully eradicated from the main cotton growing areas of the United States. The wise use of 5% non-Bt cotton as refugee has provided successful control over this pest in Australia and China. The genetically engineered cotton encoding the Cry1Ac, Cry2Ab, or Cry1F protein does not have a stable insecticidal efficacy. There is fluctuation in its expression during different cotton plant growth stages. Significant reduction in Bt-toxin expression and resistance for pink bollworm has been reported especially near crop maturation. The early crop termination through early maturing varieties, harvest aid chemicals and use of growth regulators can be a key to disrupt pink bollworm diapause phase. Varieties with Bt-toxin along with several morphological and anatomical features that provide natural shelter against bollworm attack should be cultivated in the affected regions. The collective use of integrated pest management approach, sterile PBW moth release, pheromone treatments, crop management for host free period, use of early maturing varieties, natural insect pest resistant varieties, adaptation toward the shortening of crop season, use of 5% refuge crop and transgenic Bacillus thuringiensis (Bt) cotton have great impact on the management of this pest of cotton and can change the current suboptimal worse condition of the effected cotton growing areas of the world.

Agricultural spreading of dewatered sewage sludge from wastewater treatment plants is economically profitable but care must be taken to ensure that there is neither degradation of the agronomic quality of the soils nor contamination of them in the long term, particularly by accumulation of heavy metals. To evaluate the variability of the sludge in a given geographical area, we studied the sludge coming from five treatment plants in northern Algeria. We determined parameters that account for the agronomic quality of sludges and total content of Ag, Cd, Co, Cr, Cu, Ni, Pb, Ti and Zn. We evaluated the bioavailability of theses metals by determining their speciation by sequential extraction, each metal being distributed among five fractions: easily exchangeable, acido-soluble, bound to carbonates and partly to Fe-sulphides, bound to Fe- and Mn-oxides, bound to organic matter or sulphides, contained in poorly soluble minerals. We found that all the analysed sludges had satisfactory properties from an agronomic quality point of view. High total Ni content indicated that three sludges were not spreadable under French or Chinese regulations. Metal speciation, however, showed that Ni was contained in very poorly bioavailable fractions, and therefore presented a low risk in the soils concerned. In contrast, the total Cu was below the regulatory limit values, but contained in very bioavailable fractions with a risk of toxic effects by accumulation over less than 10 years. These results showed that regulations must take into account the bioavailability with regard to the characteristics of the soils on which sludge will be spread. Metal speciation in the sludge also made it possible to identify the zone of the sewerage network on which the sources of contamination must be sought and gave indications on the nature of these sources.

This field study was performed to assess the variation in chemical and agronomic properties and total and extractable concentrations of heavy metals in soils fertilized with regulated doses of urban sewage sludge (USS) for 6 consecutive years in the framework of an agronomic treatment program. Chemical and agronomical properties, total contents and extractable concentrations of Cd, Cr, Cu, Hg, Ni, Pb and Zn were determined in agricultural soils treated with USS for 6 consecutive years, agricultural soils cultivated using mineral fertilizers and uncultivated soils representative of the local geochemical background. USS application caused a decrease in pH and an increase in extractable concentrations of Cr, Cu, Pb and Zn. No organic carbon, total nitrogen and total phosphorus enrichment trend was observed in the treated soils due to biodegradation of the organic compounds supplied by USS. The decomposition of USS organic matter was presumably the main process responsible for the pH decrease in the USS-fertilized soils. There was no heavy metal accumulation in treated soils, and total heavy metal contents were below the corresponding maximum threshold concentrations set by European and Italian legislation. Increased availability of Cr, Cu, Pb and Zn was found in treated soils due to an increase in their extractable concentrations in the treatment period. The results of this study suggest that the environmental risks related to the accumulation and availability of heavy metals in agricultural soils fertilized with USS are limited when treatment observes recommended doses in agronomic treatment programs.