Artificial neural networks as a tool for seasonal forecast of attack intensity of Spodoptera spp. in Bt soybean.

Soybean (Glycine max) is the world's most cultivated legume; currently, most of its varieties are Bt. Spodoptera spp. (Lepidoptera: Noctuidae) are important pests of soybean. An artificial neural network (ANN) is an artificial intelligence tool that can be used in the study of spatiotemporal dynamics of pest populations. Thus, this work aims to determine ANN to identify population regulation factors of Spodoptera spp. and predict its density in Bt soybean. For two years, the density of Spodoptera spp. caterpillars, predators, and parasitoids, climate data, and plant age was evaluated in commercial soybean fields. The selected ANN was the one with the weather data from 25 days before the pest's density evaluation. ANN forecasting and pest densities in soybean fields presented a correlation of 0.863. It was found that higher densities of the pest occurred in dry seasons, with less wind, higher atmospheric pressure and with increasing plant age. Pest density increased with the increase in temperature until this curve reached its maximum value. ANN forecasting and pest densities in soybean fields in different years, seasons, and stages of plant development were similar. Therefore, this ANN is promising to be implemented into integrated pest management programs in soybean fields.

Morinda citrifolia Essential Oil: A Plant Resistance Biostimulant and a Sustainable Alternative for Controlling Phytopathogens and Insect Pests.

With the growing demand for sustainable and safe agricultural practices, plant compounds emerge as a solution for biological activities. Here, we evaluated the potential of using Morinda citrifolia essential oil to induce plant resistance and to control phytopathogens (Curvularia lunata) and insect pests (Daubulus maidis). We conducted a chromatographic analysis to unveil the essential oil components. We also quantified the activity levels of antioxidant enzymes and chitinase for resistance induction. The antifungal action was evaluated through disease progression and the inhibition of mycelial growth in addition to in silico studies that made it possible to predict the interaction site between the fungal protein and the compounds. We assessed the toxicity and repellent actions towards the D. maidis. Octanoic acid (58.43%) was identified as the essential oil major compound. Preventive treatment with essential oil and octanoic acid (25.0 µL mL-1) increased not only the plant defense activities (i.e., the activity of the enzymes superoxide dismutase, catalase, phenol peroxidase, ascorbate peroxidase, and chitinase) but also controlled Curvularia leaf spot. The stable interactions between octanoic acid and tyrosine-tRNA ligase from C. lunata suggested protein synthesis inactivation. The essential oil inhibited 51.6% of mycelial growth, and this effect was increased to 75.9% with the addition of adjuvants (i.e., angico gum). The essential oil reduced 76% of the population of D. maidis adults and repelled 50% of the number of D. maidis after 48 h under field conditions. The repellency effect in the field reduced the population of D. maidis adults, transmitters of the stunting complex, by 50%. The results highlight the potential of M. citrifolia as a resistance activator, fungicide, insecticide, and an effective biorational alternative.

Optimizing Corn Crop Protection: The First Sampling Plan for Controlling Dalbulus maidis (Hemiptera: Cicadellidae).

Corn (Zea mays) is the most widely planted crop in the world. Dalbulus maidis (Hemiptera: Cicadellidae) is currently a primary corn pest. The starting point for the development of pest control decision-making systems is the determination of a conventional sampling plan. Therefore, this study aimed to determine a practical conventional sampling plan for D. maidis in corn crops. Insect density was evaluated in 28 commercial fields. Subsequently, D. maidis densities were sampled from fields ranging from 1 to 100 ha. Insect density conformed to a negative binomial distribution in 89.29% of the fields. The insect densities determined using the sampling plan had a low error rate (up to 15%). Sampling time and costs ranged from 2.06 to 39.45 min/ha and 0.09 to 1.81 USD/ha for fields of 1-100 ha, respectively. These results provide the first precise and representative conventional sampling plan for scouting D. maidis adults grown in corn fields. Therefore, the conventional sampling plan for D. maidis determined in this study is practical and can be incorporated into integrated pest management programs for corn crops owing to its representativeness, precision, speed, and low cost.

Behavioral and physiological responses of Girardia tigrina exposed to polyethylene microplastics.

Microplastic particles appear in great abundance and variety in freshwater ecosystems across the globe, spanning lakes and rivers, with increasingly frequent exposure of aquatic organisms. Studies on the mechanisms of any effects of plastic particles are still scarce, particularly in relation to the regenerative capacity of biota, for which there is no established model organism; however, planaria have shown sensitivity for assessing these risks to the aquatic environment. Thus, the present study aimed to investigate the behavioral and regeneration responses of the freshwater planaria Girardia tigrina exposed to polyethylene (PE) microplastics (MPs) incorporated into their food source. The greatest effect was observed on planarian regeneration, which was manifested at 10 µg/mg liver. Planaria reproduction and fertility were affected at 50 µg/mg liver; however, planaria locomotion was not affected at the concentrations evaluated. Mid-infrared absorption spectroscopy (FT-IR) was used to identify the constituent polymers, and ingestion of the polyethylene microplastic by the planaria was confirmed by infrared spectroscopy. The results highlight the potential adverse effects of exposure to polyethylene microplastic and show that the reproductive behavior and regeneration of a freshwater organism can be indicators of toxicity resulting from environmental pollution.

Ecotoxicological evaluation of effluent from bovine slaughterhouses disinfected by peracetic acid (PAA) using the bioindicator Girardia tigrina.

The evaluation of the ecotoxicological effects of the effluent after treatment with peracetic acid is relevant to help establish reference concentrations for the disinfection process and waste recovery. Therefore, the objective of this work was to evaluate the ecotoxicity of effluent from a bovine slaughterhouse treated with peracetic acid on Girardia tigrina. The toxicity bioassays for planaria were the acute test (LC50) and chronic assays: locomotion, regeneration, reproduction and fertility. The results showed that the effluent treated with peracetic acid showed less toxicity than the effluent without application of peracetic acid. The effluent after peracetic acid application showed a chronic toxic effect in the reduction of locomotor speed in all studied disinfectant concentrations (0.8, 1.6, 3.3 and 6.6 µg L-1 of peracetic acid) and a delay in the formation of G. tigrina photoreceptors at the concentration of 6.6 µg L-1 of peracetic acid. Peracetic acid concentrations of 0.8, 1.6 and 3.3 µg L-1 were not toxic for blastema regeneration, photoreceptor and auricle formation, fecundity and fertility. In addition, this study assists in defining doses of peracetic acid to be recommended in order to ensure the wastewater disinfection process without causing harm to aquatic organisms.

A MaxEnt Model of Citrus Black Fly Aleurocanthus woglumi Ashby (Hemiptera: Aleyrodidae) under Different Climate Change Scenarios.

The citrus blackfly (CBF), Aleurocanthus woglumi Ashby, is an exotic pest native to Southeast Asia that has spread rapidly to the world's main centers of citrus production, having been recently introduced to Brazil. In this study, a maximum entropy niche model (MaxEnt) was used to predict the potential worldwide distribution of CBF under current and future climate change scenarios for 2030 and 2050. These future scenarios came from the Coupled Model Intercomparison Project Phase 6 (CMIP6), SSP1-2.6, and SSP5-8.5. The MaxEnt model predicted the potential distribution of CBF with area under receiver operator curve (AUC) values of 0.953 and 0.930 in the initial and final models, respectively. The average temperature of the coldest quarter months, precipitation of the rainiest month, isothermality, and precipitation of the driest month were the strongest predictors of CBF distribution, with contributions of 36.7%, 14.7%, 13.2%, and 10.2%, respectively. The model based on the current time conditions predicted that suitable areas for the potential occurrence of CBF, including countries such as Brazil, China, the European Union, the USA, Egypt, Turkey, and Morocco, are located in tropical and subtropical regions. Models from SSP1-2.6 (2030 and 2050) and SSP5-8.5 (2030) predicted that suitable habitats for CBF are increasing dramatically worldwide under future climate change scenarios, particularly in areas located in the southern US, southern Europe, North Africa, South China, and part of Australia. On the other hand, the SSP5-8.5 model of 2050 indicated a great retraction of the areas suitable for CBF located in the tropical region, with an emphasis on countries such as Brazil, Colombia, Venezuela, and India. In general, the CMIP6 models predicted greater risks of invasion and dissemination of CBF until 2030 and 2050 in the southern regions of the USA, European Union, and China, which are some of the world's largest orange producers. Knowledge of the current situation and future propagation paths of the pest serve as tools to improve the strategic government policies employed in CBF's regulation, commercialization, inspection, combat, and phytosanitary management.

Reference genes for Eucalyptus spp. under Beauveria bassiana inoculation and subsequently infestation by the galling wasp Leptocybe invasa.

Relative gene expression analysis through RT-qPCR is an important molecular technique that helps understanding different molecular mechanisms, such as the plant defense response to insect pests. However, the use of RT-qPCR for gene expression analysis can be affected by factors that directly affect the reliability of the results. Among these factors, the appropriate choice of reference genes is crucial and can strongly impact RT-qPCR relative gene expression analyses, highlighting the importance in correctly choosing the most suitable genes for the success of the analysis. Thus, this study aimed to select and validate reference genes for relative gene expression studies through RT-qPCR in hybrids of Eucalyptus tereticornis × Eucalyptus camaldulensis (drought tolerant and susceptible to Leptocybe invasa) under conditions of inoculation by the Beauveria bassiana fungus and subsequent infestation by L. invasa. The expression level and stability of eleven candidate genes were evaluated. Stability was analyzed using the RefFinder tool, which integrates the geNorm, NormFinder, BestKeeper, and Delta-Ct algorithms. The selected reference genes were validated through the expression analysis of the transcriptional factor EcDREB2 (dehydration-responsive element-binding protein 2). For all treatments evaluated, EcPTB, EcPP2A-1, and EcEUC12 were the best reference genes. The triplets EcPTB/EcEUC12/EcUBP6, EcPP2A-1/EcEUC12/EcPTB, EcIDH/EcSAND/Ecα-TUB, EcPP2A-1/Ecα-TUB/EcPTB, and EcPP2A-1/EcUPL7/EcSAND were the best reference genes for the control plants, mother plants, plants inoculated with B. bassiana, plants infested with L. invasa, and plants inoculated with B. bassiana and subsequently infested with L. invasa, respectively. The best determined reference genes were used to normalize the RT-qPCR expression data for each experimental condition evaluated. The results emphasize the importance of this type of study to ensure the reliability of relative gene expression analyses. Furthermore, the findings of this study can be used as a basis for future research, comprising gene expression analysis of different eucalyptus metabolic pathways.

Endophytic colonization of five Trichoderma species and their effects on growth of a Eucalyptus hybrid.

The study aimed to evaluate the effectiveness of endophytic colonization via leaf and root inoculation of five Trichoderma species in a Eucalyptus hybrid, as well as the effects of inoculation on plant growth. The experimental design was completely randomized in a 6 × 2 factorial scheme. Plant growth was evaluated during the experimental period at three different times: 20 days after inoculation (d.a.i), 40 d.a.i., and 60 d.a.i. A statistical difference was observed between the inoculation methods during each period and between the Trichoderma species. Plants inoculated with T. asperellum showed the greatest growth among the treatments. Root-inoculated plants produced the greatest growth response. This showed that the presence of Trichoderma in the roots assisted in nutrient assimilation, promoted greater plant growth, when compared with leaf-inoculated plants. Evaluation of the effectiveness of endophytic colonization was performed at each sampling period by collecting leaf samples, and at 60 d.a.i., by collecting leaf, stem, and root samples. T. longibrachiatum and T. harzianum were isolated from leaves at 20 d.a.i., with an increase in the number of colonized plants throughout the evaluation of leaf-inoculated plants. In root-inoculated plants, treatment with T. longibrachiatum, T. harzianum, and T. asperellum presented the highest endophytic colonization in the stem and root samples (at 60 d.a.i.).

The combined effects of microbial insecticides and sodium chloride on the development and emergence of Chironomus xanthus.

BACKGROUND: Freshwater organisms are facing increasing salinity levels, not only due to natural environmental processes, but also human activities, which can cause several physiological adaptations to osmotic stress. Additionally, these organisms might also have to deal with contamination by microbial insecticides. Our main goal was to use Chironomus xanthus to assess the chronic effects of increasing the salinity and commercial formulations of the microbial insecticides based on Bacillus thuringiensis subs. kurstaki (Btk) and Beauveria bassiana (Bb) as active ingredients, respectively. RESULTS: A significant interaction of growth was observed between the biopesticide based on Bb and NaCl on the larvae of C. xanthus. Single exposure to NaCl and each one of the formulations demonstrated deleterious impacts not only on larval development, but also on the emergence success and emergence time of this nontarget insect, with potential consequences for freshwater ecosystems due to cascading effects. CONCLUSION: The chronic effects induced by both bioinsecticides show that these formulations can have environmental impacts on nontarget freshwater insects. © 2023 Society of Chemical Industry.

What does not kill it makes it stronger! The tolerance of the F1 larvae of Chironomus xanthus to a neonicotinoid insecticide formulation.

Thiamethoxam (TMX) is a systemic neonicotinoid that acts as a partial agonist of the nicotinic acetylcholine receptors (nAChRs). However, target species have shown resistance to formulations based on such neonicotinoids, which can also be expected for non-target insects. This research aimed to study the effects of a formulation based on TMX [Cruiser® 350 FS (CRZ)] on the life traits of Chironomus xanthus filial generation (F1) and compare it with the parental generation (P). Environmentally relevant concentrations of CRZ significantly decreased larvae growth P generation , also slowing and decreasing their emergence. Larvae of the F1 generation were less sensitive than their parents, suggesting that the progeny were able to thrive and perform basic physiological functions better than the parental generation. Our results highlight that insect resistance to neonicotinoids may be associated with the better performance of the filial generation, which is related to the change in affinities of the active ingredient for the sub-units constituting the nAChRs subtypes of F1 organisms, inherited from P organisms that were able to survive and reproduce. Moreover, further studies using biochemical and omics tools should be performed to disentangle the specific changes occurring at the nAChRs throughout insect development.

Sequential Sampling Plans for Thrips (Thysanoptera: Thripidae) in Soybean Crops With Insecticide Applications Using Tractor or Airplane.

Sampling plans are an essential part of integrated pest management programs. Sequential sampling plans enable rapid and low-cost assessment of pest densities. Thrips are emerging pests in soybean crops, and the main method used in pest control is chemical. In soybean crops, insecticides are applied mainly using tractors or airplanes. Thus, this work aimed to determine sequential sampling plans for thrips in soybean crops with insecticide applications using a tractor or airplane. Data were collected in 56 soybean fields, and each field was 20 ha. Sampling plans were determined and validated. The lower (m0) and upper (m1) limits of the sequential sampling plans were: m0 = 1.72 and m1 = 3.43 (by tractor applications) and, m0 = 2.27 and m1 = 4.53 thrips. sample-1 (by airplane applications). The slope (S) and the lower (h0) and upper (h1) intercepts of the sequential sampling plans were: S = 2.42, h0 = -5.79, and h1 = 5.79 (by tractor applications) and, S = 3.19, h0 = -6.83, and h1 = 6.83 (by airplane applications). Sequential sampling plans allowed for correct decisions to be made in all situations using a maximum of 10 samples. The sequential plan reduced the sampling effort by over 87% compared to conventional sampling plans. Therefore, these control decision-making systems have proven feasible and advantageous for implementing integrated pest management programs for controlling thrips species in soybean crops.

The multigenerational effects of clothianidin on Chironomus xanthus: Larvae exposed to this acetylcholine super agonist show no clear resistance.

Clothianidin (CLO) is an insecticide belonging to the second-generation class of neonicotinoids. In this study, we evaluated how CLO affects the survival and the complete life cycle of the tropical insect Chironomus xanthus, a non-target species, considering the Parental (P) and Filial (F1) generations. We found a 48 h-lethal concentration (LC50) of CLO of 3.78 µg/L. The lowest observed effect concentrations (LOECs) were: i) for body growth and head capsule width in P generation = 47.3 ng/L CLO; ii) for body growth and head capsule width in F1 generation larvae = 80 and 36.4 ng/L CLO, respectively; iii) for cumulative emergence it was 80 ng/L CLO in the P generation, while there was no significant difference in the F1 generation; iv) for total developmental time for males and females = 61.53 ng/L in P generation; v) in the F1 generation, the LOEC was determined to be 36.4 ng/L for males and 80 ng/L for females; vi) The number of total hatched eggs and total hatched eggs/female had LOECs of 36.4 ng/L CLO for both generations. Our study reveals that environmentally relevant concentrations of the CLO-based insecticide are highly toxic to C. xanthus. It also shows that the F1 generation, resulting from parents exposed to CLO was not clearly resistant to the insecticide. This fact might be explained by the different effects observed for males and females of F1 generation. Understanding the sub-types of acetylcholine receptors present on target and non-target insect species and toxicological effects of neonicotinoids seems to be desirable for the insecticide industry to deal with insect pests and the environmental protection of non-target organisms.

Cell death and changes in primary metabolism: the onset of defence in Eucalyptus in the war against Leptocybe invasa.

BACKGROUND: Here, we investigated changes in primary metabolism and cell death around oviposition sites in two hybrid clones of Eucalyptus with different degrees of resistance to Leptocybe invasa Fisher & La Salle (Hymenoptera: Eulophidae), as well as tolerance to water deficiency. RESULTS: We showed that apices of the resistant clone with oviposition had a higher content of amino acids, organic acids and the compound putrescine compared with those of the susceptible clone with oviposition. By contrast, apices of the resistant clone with oviposition had lower sugar and pyruvate organic acid content than those of the susceptible clone with oviposition. Small areas of necrosis were induced around the oviposition sites in the stem apices of Eucalyptus 24 h after infestation. The resistant clone developed larger necrotic areas that showed progressive increases 24-72 h after infestation compared with the susceptible clone, in which cell death was significantly lower and no changes were observed in necrotic area over time. Thus, the programmed death of cells around the egg, modulated by several amino acids, is likely the first defence response of Eucalyptus against L. invasa. CONCLUSION: Our results serve as the basis for the early identification of key metabolites produced in plants in defence against galling insects. © 2022 Society of Chemical Industry.

Do bio-insecticides affect only insect species? Behavior, regeneration, and sexual reproduction of a non-target freshwater planarian.

Bio-insecticides have been increasingly used worldwide as ecofriendly alternatives to pesticides, but data on their effects in non-target freshwater organisms is still scarce and limited to insects. The aim of this study was to determine the lethal and sub-lethal effects of the bio-insecticides Bac Control (based on Bacillus thuringiensis kurstaki-Btk) and Boveril (based on Beauveria bassiana-Bb) on regeneration, behavioral, and reproductive endpoints of the freshwater planarian Girardia tigrina. The estimated LC50-48h were > 800 mg a.i./L for Btk and 60.74 mg a.i./L for Bb. In addition, exposure to Btk significantly decreased locomotion and feeding activities of planarians (lowest observed effect concentration (LOEC) of 12.5 mg a.i./L Btk) and fecundity rate (LOEC = 3.12 mg a.i./L Btk), whereas exposure to Bb significantly delayed regeneration (LOEC = 0.75 mg a.i./L Bb) and decreased fecundity rate (1.5 mg a.i./L Bb) of planarians. Thus, both bio-insecticides induced deleterious sub-lethal effects on a non-insect freshwater invertebrate species. However, only Bb-based formulation affected the survival, fecundity rate, and regeneration at concentrations below the maximum predicted environmental concentration (PEC = 247 mg/L). Thus, care should be taken when using such formulations as alternatives to chemical insecticides near aquatic ecosystems.

Fenton-type process using peracetic acid: Efficiency, reaction elucidations and ecotoxicity.

Recent studies on Fenton-type processes involving peracetic acid (PAA) stimulated further development of advanced oxidative processes (AOPs). The objective of this work was to provide new information about such processes, elucidate their reaction mechanisms both experimentally and theoretically, and verify their possible uses. The Fenton-type reaction of PAA with Fe3+ exhibited a greater dye degradation efficiency than the Fenton process, while the efficiency of the PAA reaction with Fe2+ was very close of Fenton process. Moreover, the processes photocatalyzed by solar radiation demonstrated comparable efficiencies due to the photoreduction of Fe3+ to Fe2+. By conducting theoretical calculations, it was found that the formation of oxidizing radicals during the reaction of PAA with Fe2+ was not thermodynamically favorable and, therefore, unsuitable for practical use. In contrast, the processes occurred in the PAA/Fe3+ system included thermodynamically spontaneous reactions that generated peroxyl (CH3C(O)OO•), alkoxyl (CH3C(O)•), and hydroperoxyl (HO2•) radicals. The ecotoxicological tests demonstrated that the toxicity of the PAA to the organism Dugesia tigrina can be attributed to the presence of H2O2.

First report of Colletotrichum chrysophillum causing cassava anthracnose in Brazil.

Cassava (Manihot esculenta Crantz) has significant socioeconomic relevance in Brazil and other developing countries, as one of the main sources of carbohydrates for human and animal consumption (De Oliviera et al., 2011). Among the cassava crop diseases, anthracnose is one of the main limiting factors for production and may be caused by species like Colletotrichum plurivorum, C. karstii, C. fructicola, and C. siamense (Bragança et al., 2016; Liu et al., 2019; Oliveira et al., 2016; Sangpueak; Phansak; Buensanteai, 2018). Severity in the field is variable, depending on the resistance of the variety used and is also highly influenced by the climate, being the most severe disease under high humidity and high temperature. Under these conditions, it can cause losses of up to 100%. In 2019, cassava leaves presenting dark brown necrotic injuries of different sizes and irregular borders-typical anthracnose symptoms- were collected from commercial plantations in the states of Pará and Tocantins, Brazil. Symptomatic tissue fragments were superficially disinfected, placed in plates with potato dextrose agar (PDA), and incubated under 25 ± 2 °C for seven days. In the 56 isolates used in the morphological identification, the colonies were white and gray at the top and dark gray in the bottom with sector formation. The conidia were hyaline, cylindrical, and aseptic, 10.04 to 17.83 µm long × 3.29 to 5.75 µm wide. These phenotypical characteristics were similar to those of C. gloeosporioides lato sensu species (Weir et al., 2012). Genomic DNA was extracted from two representative isolates (UFT/Coll69, collected in the municipality of Casa de Tábua-PA; UFT/Coll82, collected in Pau Darco-PA) and the APN2 / MAT-IGS, DNA lyase (Apn2), and glyceraldehyde-3-phosphate dehydrogenase-IGS (GAP2-IG) intergenic spacers were amplified and sequenced. The nucleotide sequences were deposited in the GenBank (accession numbers: MT409462, MT396231, MT759633, MT396239, MT396232, MT800846). The BLASTn (Basic Local Alignment Search Tool) showed a 99 to 100% similarity with Colletotrichum chrysophillum. The maximum likelihood phylogenetic analysis grouped the isolates in the C. chrysophillum clade, with a high bootstrap value (98%). Based on morphocultural characteristics and the phylogenetic analysis, the isolates associated with M. esculenta anthracnose were identified as C. chrysophillum, with a frequency of 6.67% among Colletotrichum colonies isolated from cassava leaves. The inoculation of three isolates was carried out in three plants, three leaves for each plant, by spraying spore solution with a concentration of 1×106 conidia / ml, without wounding the leaves and placed in a humid chamber at 25 ° C for ten days. Control plants were inoculated with sterile distilled water. From the 2nd day after inoculation, small irregular necrotic lesions appeared that increased in size over time, while control plants remained asymptomatic. Both were pathogenic and the symptoms caused after inoculation were similar to each other and to those observed in the field. In Brazil, anthracnose by C. chrysophillum was reported in cashew (Veloso et al., 2018) and banana trees (Vieira et al., 2017). To our knowledge, this is the first report of cassava anthracnose disease by C. chrysophillum.

Lethal and sublethal effects of the saline stressor sodium chloride on Chironomus xanthus and Girardia tigrina.

Salinization in freshwaters is gradually increasing as a result of human activities and climatic changes. Higher salt content causes stress for freshwater organisms. Sodium chloride (NaCl) is among the most frequently occurring salts in freshwater ecosystems. The objective of the present study was to investigate the lethal and sublethal effects of NaCl on freshwater ecosystems, using as test organism the dipteran Chironomus xanthus and the planarian Girardia tigrina. Acute tests showed that C. xanthus was more sensitive (48-h LC50 (median lethal concentration) of 2.97 g NaCl L-1) than G. tigrina (48-h LC50 of 7.77 g NaCl L-1). C. xanthus larvae growth rate (larvae length and head capsule width) was significantly reduced under exposure to concentrations as low as 0.19 g L-1 NaCl and higher. A delay in the emergence time (EmT50) was also demonstrated for the same concentration. Sublethal NaCl effects in G. tigrina included feeding inhibition (LOEC (lowest observed effect concentration) of 0.4 g L-1), reduced locomotion (LOEC = 0.2 g L-1), and 24-48-h blastema regeneration (LOEC = 0.2 g L-1 and 0.1 g L-1, respectively). The results demonstrated the toxicity of NaCl to C. xanthus and G. tigrina including sublethal effects that can result in negative consequences for populations in natural freshwaters under salinization.

Effects of lethal and sublethal concentrations of peracetic acid and active chlorine of calcium hypochlorite on Chironomus xanthus.

Freshwater ecosystems are vulnerable to residual concentrations of chemical agents from anthropogenic activities, and the real impacts of such compounds can only be evaluated accurately using ecotoxicological tests. The assessment of ecotoxicological effects of peracetic acid (PAA) and the active chlorine of calcium hypochlorite (Ca(ClO)2) on the insect Chironomus xanthus Meigen (Diptera: Chironomidae) is highly relevant as there are few reports on its effects in fresh water ecosystems. To our best knowledge, this is the first study to assess the chronic toxicity of the compounds to C. xanthus. The toxicity bioassays for C. xanthus included the acute effect (CL50) and the chronic effects based on body length, head width, and cumulative emergence. The results obtained in the acute effect tests indicated that the active chlorine of Ca(ClO)2 is 14 fold more toxic than PAA to C. xanthus. In sublethal evaluations, the active chlorine of Ca(ClO)2 presented higher toxicity than PAA in terms of percentage emergence, body development, and head width. In general, the results showed lower PAA toxicity relative to the active chlorine of Ca(ClO)2, demonstrating that PAA is a promising substitute for chlorinated disinfectants. In addition, the study facilitates the establishment of reference values for the safe release of effluents treated with PAA into water bodies.

Geostatistical Assessment of Frankliniella schultzei (Thysanoptera: Thripidae) Spatial Distribution in Commercial Watermelon Crops.

Spatial distribution studies of insect pests make it possible to determine their colonization and dispersal patterns. Watermelon (Citrullus lanatus (Thunb.) Matsum. et Nakai) is among the most frequently consumed fruits in the world, and the common blossom thrips, Frankliniella schultzei (Trybom) (Thysanoptera: Thripidae), is one of the most important insect pests of this plant. The objective of this study was to determine the spatial distribution of F. schultzei in commercial watermelon crops using geostatistics. The studied F. schultzei populations presented an aggregated distribution. The colonization of thrips began at the borders of the crops, especially in the areas located in the opposite direction to that of the prevailing winds. The highest densities of thrips occurred in crops that had cucurbits in the surrounding areas. When monitoring for F. schultzei populations, greater attention should be given to sampling that part of the crop located in the opposite direction to that of the prevailing winds because this is where colonization begins. Even at low densities, the aggregation points of thrips in the crop should be located and controlled so that they do not cause damage. In sampling programs for F. schultzei, samples should be taken at distances greater than 9 m apart because this is the distance up to which densities of this species show spatial dependence. Planting watermelon crops close to other cucurbits should be avoided, as these alternate hosts may act as a source of infestation by this pest.

Detection of Colletotrichum gloeosporioides in native cashew species in Brazil.

The savanna cashew (Anacardium humile A. St. Hil.) nut is a native shrub species distributed in the savanna biome of Central Western Brazil. This species is similar to the cashew (Anacardium occidentale L.) nut, and its edible pseudo-fruits have been used for various purposes. However, A. humile is at risk of extinction. One reason for this is the phytosanitary issues. Therefore, phytosanitary studies of the serious plant diseases caused by fungal pathogens are necessary. The aim of this study was to survey the savanna cashew nut (Anacardium humile) in Central Western Brazil from August 2013 to October 2014. Serious damage caused by anthracnose to the plant's leaves and fruits was consistently detected. The pathogen fungal species was Colletotrichum gloeosporioides. It was identified by morphological characteristics and molecular analyses. Additional experiments showed evidence that C. gloeosporioides can be transmitted by cashew seeds. We observed anthracnose symptoms on the surfaces of the floral peduncle, leaves, and peduncle of the A. humile cashew nuts. The genomic DNA sequences of the selected strains for molecular characterization have had 99% identity with the analogous sequences of C. gloeosporioides. Naturally occurring C. gloeosporioides infection of the leaves of A. humile was low (20.3%) compared with that of the nuts (79.7%). Our results can be used to design strategies to prevent the introduction and establishment of C. gloeosporioides in new areas. They can also be helpful in monitoring programs in areas with a current occurrence of C. gloeosporioides. Finally, these results can be used in future research plans of C. gloeosporioides infection management.