BACKGROUND: A high dose/refuge combination is the main tactic recommended for mitigating resistance selection of target herbivore species in crops expressing insecticidal proteins of the bacterium Bacillus thuringiensis (i.e. Bt proteins). The tactic consists of the simultaneous use of Bt crops expressing high levels of the Bt protein associated with neighboring areas of refuge of the same non-Bt crop species. Nonetheless, the approach faces controversy regarding its effectiveness and scale of adoption, at least in some regions. One concern focuses on its potential impact on the arthropod community, including its short-term and spatially dependent impact considering the likely biota spillover effect between Bt and non-Bt neighboring areas. Thus, the eventual spillover of Bt maize targeted and non-targeted arthropods was surveyed along transects extending from the refuge border to the center of the Bt maize area. RESULTS: Arthropods were collected throughout the maize vegetative and reproductive stages. A total of 85 arthropod species were collected, but their richness and abundance did not vary with distance from the refuge. By contrast, cultivation season played a significant role in distinguishing the arthropod communities. Refuge distance from the sampling point within Bt-fields did not significantly affect the food web metrics, unlike season, which affected the number of nodes integrating each food web. Winter maize cultivation exhibited higher arthropod diversity and combined values of species numeric abundance and biomass at each trophic level. CONCLUSIONS: No arthropod spillover was evident between the refuge edge and Bt maize, adding further controversy to the tactic currently subjected to lower usage in the region with a disputed cost-benefit relationship, because not even the target and its interdependent species were affected.

Koerner et al., 2017). Indeed, every ecosystem is potentially vulnerable to the negative impact of stressors and some anthropogenic activities cause severe environmental stress, including deforestation, global warming, and exotic species invasion, to name a few (

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The intrinsic rate of natural increase of a population (rm) has been in focus as a key parameter in entomology and acarology. It is considered especially important in studies of predators that are potential biological control agents of fast-growing pests such as mites, whiteflies and thrips. Life-table experiments under controlled laboratory conditions are standard procedures to estimate rm. However, such experiments are often time consuming and may critically depend on the precise assessment of the developmental time and the fecundity rate early in the reproductive phase. Using selected studies of predatory mites with suitable life-table data, we investigated whether and how measurements of growth rates can be simplified. We propose a new method for estimating rm from partial life tables, in which the researcher can choose a level of precision based on a stand-in measure of relative error. Based on this choice, the procedure helps the researcher to decide when a life-table experiment can be terminated. Depending on the chosen precision, significant amounts of experimental time can be saved without seriously compromising the reliability of the estimated growth parameter.

Plants produce volatiles in response to attacks by arthropod herbivores, and these volatiles can be used as cues by natural enemies to find their prey. Because these volatiles are within a variety of other odour blends, here referred to as background volatiles, natural enemy response towards prey-associated plant volatiles may be affected. Thus, this research aimed to evaluate the effect of mixing blends of volatiles under controlled conditions on the foraging behaviour of the predatory mite Phytoseiulus macropilis. Moreover, we investigated whether background volatiles and other cues in a release-recapture experiment under semi-field conditions would affect the response of this predatory mite. Mixing the blends emitted by Tetranychus urticae- infested bean plants with uninfested coriander under controlled conditions, led to a preference of predatory mites towards blends emitted by infested-bean alone over the combination. Also, I found that the volatiles of an uninfested mint plant were attractive to the predatory mite when offered against no odour source. Besides, released-recapture experiments showed a low recapture percentage for every combination of plants tested, suggesting that background volatiles from both companion plants and the environment might have hindered P. macropilis in localizing the plants with prey. These results indicate that experiments under semi-field conditions have a higher accuracy in predicting natural enemy behaviour when compared to olfactometer experiments, that in spite of its importance, does not allow us to predict a behaviour under more complex conditions. Keywords: T. urticae. Herbivore-induced plant volatiles. Companion plants. Semi-field experiments.