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BACKGROUND The Old‐World bollworm, Helicoverpa armigera (Hübner), was recently documented attacking cotton and soybean plants in Brazil; however, restricted basic knowledge on host plant interactions and landscape use in Brazil have limited the effectiveness of control measures. In this study, we evaluated the suitability of different crops commonly cultivated in Brazil as hosts for H. armigera and H. zea, and examined their contribution to the establishment and size of H. armigera and H. zea field populations. We also estimated the proportions of H. armigera and H. zea moths that used cotton, noncotton C3 plants, and C4 plants as hosts in four regions in Brazil through the length of the cropping season. RESULTS: Viability of H. armigera larvae was highest on cotton (46.1%), followed by millet (39.5%), sorghum (31.2%), soybean (24.2%), and maize (21.1%). Noncotton C3 hosts served as the major source of H. armigera moths in all regions evaluated, and C4 hosts were a source of H. armigera mainly in regions where winter maize is typically cultivated. H. armigera moths that used cotton plants as natal hosts were observed during the reproductive stage of the crop mainly in the state of Bahia. Only C4 host plants were a consistent source of H. zea moths, primarily when maize was in the reproductive stage. H. armigera individuals were the main species infesting cotton and soybean fields while H. zea individuals were the main species infesting maize ears. CONCLUSIONS: Regional differences in the host use and population dynamics of H. armigera among the regions evaluated may be attributed to variation in alternative host utilization (crops, noncrops, and weeds) and the possible occurrence of facultative diapause and or migration. [ABSTRACT FROM AUTHOR]

Background: Spodoptera frugiperda is a destructive pest that often imposes difficult management due to its high polyphagy and rapid insecticide resistance evolution. Knowledge of species diversification, population structure, and host preference can aid efforts to manage pest populations. Here, we investigated the patterns of hybridization, genetic structure, and gene flow in S. frugiperda populations, discussing how we can apply this knowledge to insect resistance management programs in South America. Results: The corn‐strain CS‐h2 of S. frugiperda was the most frequent haplotype in all sampled populations. Spodoptera frugiperda populations are experiencing demographic expansion, and the ecoregions partially explain the genetic structure and not strains. We did not find a correlation between gene flow and susceptibility levels to flubendiamide and lufenuron insecticides, but populations with high LC50 sent a great number of migrants to all other locations, maintaining resistance alleles in the geographic range. Conclusion: High levels of population admixture, including between corn‐ and rice‐strains, were found in sampled populations. We showed that S. frugiperda immigrants will not necessarily cause an increase in LC50 upon arrival in a new location but will assure the constant presence of resistance alleles in the area. Increases in LC50 largely depend on the local pesticide management adopted in the areas. Our results indicate that pesticide resistance management must be adopted on a local or small regional scale. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The coffee leaf miner, Leucoptera coffeella (Guérin-Mèneville & Perrottet, 1842), probably infested coffee plants in Neotropical America during the 19th century. The species subsequently became a key pest of coffee plants in Brazil, but not in Colombia, the two main coffee producers in the region. The contrasting importance of the coffee leaf miner in Brazil and Colombia may be the result of the evolutionary and demographic history of this species. Therefore, our goal was to test two alternative hypotheses regarding the possible genetic origins of this species: 1) leaf miners in both countries share the same origin and 2) the leaf miner arrived in both countries independently from distinct sources and subsequently diversified without genetic exchange between countries. Thus, DNA sequence data of 21 populations were collected (Brazil, 16; Colombia, 5), and partial sequences of their cytochrome oxidase subunit I (COI), cytochrome b (Cytb), and the nuclear internal transcribed spacer (ITS) region were obtained to test these hypotheses. Both nuclear and mitochondrial molecular markers showed low nucleotide diversity. Analyses of molecular variance indicated higher variability within population in both concatenated mitochondrial genes and ITS region (70.57 and 84.01%, respectively). Finally, geno/haplotype networks showed each central geno/haplotypes that displayed high frequency and were distributed widely in both countries. Low-frequency geno/haplotypes were at tip positions connected to the central geno/haplotypes through single mutation steps, suggesting that the Neotropical coffee leaf miner in both Brazil and Colombia consists of a single species and exhibits a common and recent genetic origin. [ABSTRACT FROM AUTHOR]

Leafminer flies are phytophagous and cosmopolitan pests. Leafminer fly outbreaks and damage to cultivated plants have steadily increased in several regions in the world., In the present study, we report host range, geographical distribution, Wolbachia infection and mitochondrial strains of leafminer fly species from eastern Brazil., Four leaf miner fly species were identified using cytochrome c oxidase subunit I DNA barcoding. Liriomyza sativae is the main pest as a result of its high polyphagy and wide distribution. Liriomyza brassicae, Liriomyza huidobrensis and Calycomyza malvae are important in Brassicaceae, Curcubitaceae and Malvaceae crops, respectively., There is no relationship among host range, geographical distribution and mitochondrial strains of leafminer fly species. We did not find Wolbachia infection in any of the specimens collected., Phylogeographical analyses suggests that there are four strains of L. sativae in the world, one of which is endemic from Brazil. The lack of shared haplotypes between Brazilian specimens and those from other world regions indicates the absence of recent gene flow of leafminer flies from Brazil with specimens from Americas and Old world. The exception is L. brassicae, which exhibits one haplotype shared among Brazil, Philippines and Sri Lanka., The host range identification and geographical isolation of leafminer fly species from Brazil comprise useful information for quarantine and pest management purposes. [ABSTRACT FROM AUTHOR]

BACKGROUND Random mating is a common assumption in studies of insecticide resistance evolution, but seldom tested despite its potential consequences. Therefore, the existing evidence of female choice and insecticide resistance in populations of the maize weevil ( Sitophilus zeamais), a key pest of stored cereals, led to the assessment of mating preferences and their association with insecticide resistance in this species. RESULTS Mixed lines of a maize weevil colony were established from field-collected populations, which after 5 months of natural breeding were selected for deltamethrin resistance for five generations, reaching over 100-fold resistance. Mating preference was significantly based on the partner size, measured as body mass ( χ2 = 5.83, df = 1, P = 0.016). Susceptible females preferred heavier males for mating ( χ2 = 5.83, df = 1, P = 0.015), a trait that was more frequently associated with deltamethrin resistance ( χ2 = 7.38, df = 1, P = 0.007). Deltamethrin resistance compromised daily fertility, although the reduced offspring production observed in matings between susceptible females and resistant males was negligible. CONCLUSION Susceptible female weevils prefer larger (and heavier) males to mate, a trait associated with deltamethrin resistance, favouring the maintenance and spread of the resistant phenotype in the population. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The tomato leaf miner Tuta absoluta is a key pest of the tomato and is of global significance. Insecticide is the primary method for controlling this pest, requiring a search for compounds with a low toxicity to nontarget organisms., We assessed the toxicity of eight insecticides to T. absoluta and its pirate bug predators Orius tristicolor, Amphiareus constrictus and Blaptostethus pallescens ( Hemiptera: Heteroptera: Anthocoridae). We also assessed the effect of insecticide synergists on their toxicity to the predators, as well as their walking response to insecticide exposure., All insecticides, with the exception of methamidophos, exhibited the minimum efficacy threshold required by the Brazilian legislation (80% efficacy) at concentrations lower than the registered label rates. Indoxacarb and chlorantraniliprole exhibited a lower toxicity to the pirate bug predators than to the tomato leaf miner., The results obtained with the synergized insecticides suggest the involvement of cytochrome P450-dependent monooxygenases as the primary detoxification enzymes minimizing insecticide toxicity in the pirate bug predators., The insecticides led to a reduction in predator walking activity, especially abamectin and indoxacarb, which significantly minimized predator exposure., The results of the present study indicate that novel insecticides, especially chlorantraniliprole, are better suited to sustainable integrated management programmes of the tomato leaf miner. [ABSTRACT FROM AUTHOR]

The genus Sitophilus (Coleoptera: Curculionidae) encompasses species of great economic importance as stored grain pests worldwide. Among these species, the maize and the rice weevils ( Sitophilus zeamais and Sitophilus oryzae, respectively) are particularly important in warmer climates. These two weevils exhibit closely morphological and ecological resemblance making difficult their proper identification and recognition of their distribution in grain-producing regions. Both species are recorded in South America and particularly in Brazil, but their respective distribution and prevalence were not yet assessed in the region. Therefore, several insect samples throughout Brazil were collected and subjected to morphological identification using male genitalia and also using molecular identification with species-specific primers designed for clear recognition of both the species. The primers were designed for the specific amplification of a gene fragment of the cytochrome oxidase subunit I, which exhibited high specificity during our preliminary experiments with insects from six populations of known species (either S. zeamais or S. oryzae). Both identification strategies provided the same results indicating prevalence of the maize weevil S. zeamais throughout the country. Two hypotheses may explain such prevalence: (i) the likely host preference of S. zeamais for maize because this is the most cultivated cereal in Brazil, and (ii) the prevalence of S. zeamais in tropical regions as compared with S. oryzae, which is more disseminated in subtropical and temperate regions. [ABSTRACT FROM AUTHOR]