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The introduction of an agricultural pest species into a new environment is a potential threat to agroecosystems of the invaded area. The phytosanitary concern is even greater if the introduced pest’s phenotype expresses traits that will impair the management of that species. The invasive tomato borer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), is one such species and the characterization of the insecticide resistance prevailing in the area of origin is important to guide management efforts in new areas of introduction. The spinosad is one the main insecticides currently used in Brazil for control of the tomato borer; Brazil is the likely source of the introduction of the tomato borer into Europe. For this reason, spinosad resistance in Brazilian populations of this species was characterized. Spinosad resistance has been reported in Brazilian field populations of this pest species, and one resistant population that was used in this study was subjected to an additional seven generations of selection for spinosad resistance reaching levels over 180,000-fold. Inheritance studies indicated that spinosad resistance is monogenic, incompletely recessive and autosomal with high heritability (h2 = 0.71). Spinosad resistance was unstable without selection pressure with a negative rate of change in the resistance level ( = −0.51) indicating an associated adaptive cost. Esterases and cytochrome P450-dependent monooxygenases titration decreased with spinosad selection, indicating that these detoxification enzymes are not the underlying resistance mechanism. Furthermore, the cross-resistance spectrum was restricted to the insecticide spinetoram, another spinosyn, suggesting that altered target site may be the mechanism involved. Therefore, the suspension of spinosyn use against the tomato borer would be a useful component in spinosad resistance management for this species. Spinosad use against this species in introduced areas should be carefully monitored to prevent rapid selection of high levels of resistance and the potential for its spread to new areas. [ABSTRACT FROM AUTHOR]

The use of Cry toxins from Bacillus thuringiensis (Bt) is a breakthrough in the cultivation of transgenic Bt plants because of its high specificity and safety for the environment. However, a serious threat to the sustainability of this technology is the potential for insect populations to develop resistance to Bt toxins. It is important to understand the pathogen-insect interactions to extend the usefulness of prod-ucts based on B. thuringiensis. Recent studies reported evidence of a tolerance mechanism associated with the immune response. Because of the importance of Alabama argillacea (Hubner, 1818) as a cot-ton pest, this research assessed its immunological alterations (cellular and humoral) when challenged with formulations of B. thuringiensis var. aizawai and B. thuringiensis var. kurstaki. The results sug-gest that the fourth instar larvae of A. argillacea do not have the potential to develop natural immune tolerance to the formulations based on B. thuringiensis. Dipel® led to a quantitative variation in all cell types, while XenTari® changed prohemocytes, plasmatocytes, granulocytes and oenocytoids. In insects treated with Dipel® there was no increase in the level of nitric oxide. These differences in response to treatments can be attributed to differences in the composition of the insecticides tested. The results indicate that the insecticide Dipel® caused significant changes in cellular and humoral immune system of fourth instar larvae of A. argillacea, while XenTari® caused only changes in the cellular immune system, furthermore Dipel® was faster to cause the cellular changes mentioned. [ABSTRACT FROM AUTHOR]