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The iota toxin (ITX) is a binary enterotoxin produced as a protoxin by Clostridium perfringens (C. perfringens) type E that is activated by proteolytic enzymes in the small intestine of infected animals. By depolymerization of the actin filaments, ITX causes cytoskeleton disorganization of cells promoting the increase of the cell permeability. Here, we conducted this review aiming to advance the understanding of enteric clostridial diseases caused by C. perfringens toxins and the specificity of ITX in the intestinal mucosa lesions. ITX consists of an enzymatic component (Ia) and a binding component (Ib). We screened the recently published histological findings of the ITX effects and its relationship with intestinal enteric diseases. Histologically, hemorrhagic necrosis and multifocal hemorrhage have been observed in the jejunum-ileum mucosa, the small intestine, and the abomasum. Although the diagnosis is still based on the presence of toxins in the intestinal contents and the clinical and/or histological history, it is important to develop novel enterotoxemic indicators capable of establishing precise methods for differentiate the actions of ITX and other toxins involved in the infectious process of C. perfringens type E.

Recent agricultural expansion into regions of the Brazilian savannah or Cerrado has improved agricultural knowledge and management practices. Under this biome’s favorable conditions, the incidence of diseases such as gummy stem blight (GSB) could be a limiting factor for some crops (i.e., Cucumis melo L.), due to high losses in productivity and fruit quality. We conducted field experiments to assess the temporal progression of the incidence and severity of GSB disease in melon plants under five pesticide treatments and three growing seasons (dry, rainy, and transition periods). Furthermore, the susceptibility of six cultivars of melon to GSB was evaluated with and without pesticide application. In the dry season, although the incidence of the disease was high and dependent on the applied pesticides, its severity was low, allowing the crop cycle to be completed and marketable fruits to be harvested. However, in the rainy and transition periods, the high incidence and severity of the disease recorded in all plants, independent of the pesticides used, resulted in a premature end to the growth of the melon crops. Moreover, the commonly cultivated cultivar (Eldorado 300) showed a higher incidence and severity of the disease than the other potential cultivars. The results suggest that melon crops should be grown exclusively under the Brazilian Cerrado conditions during the dry season, dominated by favorable climatic conditions for the melon and unfavorable conditions to the pathogen. Other cultivars need to be investigated for their suitability to this region.

Extremely low-frequency electromagnetic fields (ELF EMFs) have been shown to impact the behavior and physiology of insects. Recent studies have highlighted the need for more research to determine more specifically how they affect flying insects. Here, we ask how locust flight is affected by acute exposure to 50 Hz EMFs. We analyzed the flights of individual locusts tethered between a pair of copper wire coils generating EMFs of various frequency using high-speed video recording. The mean wingbeat frequency of tethered locusts was 18.92 ± 0.27 Hz. We found that acute exposure to 50 Hz EMFs significantly increased absolute change in wingbeat frequency in a field strength-dependent manner, with greater field strengths causing greater changes in wingbeat frequency. The effect of EMFs on wingbeat frequency depended on the initial wingbeat frequency of a locust, with locusts flying at a frequency lower than 20 Hz increasing their wingbeat frequency, while locusts flying with a wingbeat frequency higher than 20 Hz decreasing their wingbeat frequency. During the application of 50 Hz EMF, the wingbeat frequency was entrained to a 2:5 ratio (two wingbeat cycles to five EMF cycles) of the applied EMF. We then applied a range of ELF EMFs that were close to normal wingbeat frequency and found that locusts entrained to the exact frequency of the applied EMF. These results show that exposure to ELF EMFs lead to small but significant changes in wingbeat frequency in locusts. We discuss the biological implications of the coordination of insect flight in response to electromagnetic stimuli. © 2021 Bioelectromagnetics Society.

The management of the Neotropical brown stinkbug Euschistus heros (Hemiptera: Pentatomidae) in soybean fields has been heavily dependent on the application of neonicotinoid insecticides. Neonicotinoids act primarily by impairing the function of the nicotinic acetylcholine receptors of the nervous system. These compounds also target specific organs (e.g., salivary glands), which may potentiate their insecticidal efficacy. Here, we evaluated whether the exposure to the neonicotinoid imidacloprid would cause cytomorphological changes in the salivary glands of E. heros. First, we determined the lethal concentrations (LCs) of imidacloprid through contact and ingestion. Subsequently, the cytomorphology of the salivary glands were evaluated in insect groups that survived exposure to the LC5 (3.75 mg a.i./L), LC50 (112.5 mg a.i./L), or LC75 (375.0 mg a.i./L, equivalent to the recommended field rate) doses. Imidacloprid induced apoptosis and necrosis in the salivary gland cells according to the insecticide concentration and salivary gland region. All concentrations increased apoptosis and injured cells (e.g., vacuolization, chromatin condensation, swelling of organelles, and plasma membrane rupture) in the principal and accessory salivary glands. Individuals that survived exposure to the highest concentrations (i.e., LC5 and LC50) were more affected, and exhibited several necrotic cells on their main principal salivary glands. Collectively, our results indicate that imidacloprid exerts toxic effects on the non-target organs, such as the salivary glands, which increases the efficacy of this compound in the management of stink bug infestations.

Stink bugs (Pentatomidae) produce volatile chemical substances in the scent glands, with unpleasant odors that function as alarm and defense signals against natural enemies. The contents of the scent glands of the predatory Podisus nigrispinus and its prey, the phytophagous Euschistus heros were used to evaluate the behavioral interactions between these two insects. Quantitative and qualitative analyses of odor components were performed by gas chromatography (GC/FID and GC/MS) and behavioral response evaluated by video-tracking system. The chemical composition of the odor produced by P. nigrispinus and E. heros contains aldehydes and hydrocarbons. The chemical mixture has quantitative and qualitative component differences between species and sexes, with 20 compounds identified for P. nigrispinus and 17 compounds for E. heros. The compounds (E)-2-hexenal, hexenoic acid, (E)-2-decenal, tridecane, tetradecane, and pentadecane occur in both species, but with different amounts between males and females. The secretion of the scent gland of P. nigrispinus and E. heros produces repellent and irritant effects between species and between sexes of the same species, supporting the defensive function of these compounds. Chemical identification of the Pentatomidae scent gland compounds may influence in insect behavior cause side effects in other insects. Overall, these compounds can be a sustainable and novel source of insecticides with potential to agricultural pest control.

Complaints of severe damage by whiteflies in soybean fields containing genetically engineered (GE) varieties led us to investigate the role of transgenic soybean varieties expressing resistance to some insects (Cry1Ac Bt toxin) and to herbicide (glyphosate) on the population growth and feeding behavior of Bemisia tabaci (Gennadius) MEAM1 (Hemiptera: Aleyrodidae). In the laboratory, the whiteflies reared on the GE Bt soybeans had a net reproductive rate (R0) 100% higher and intrinsic rate of population increase (rm) 15% higher than those reared on non-GE soybeans. The increased demographic performance was associated with a higher lifetime fecundity. In electrical penetration graphs, the whiteflies reared on the GE soybeans had fewer probes and spent 50% less time before reaching the phloem phase from the beginning of the first successful probe, indicating a higher risk of transmission of whitefly-borne viruses. Data from Neotropical fields showed a higher population density of B. tabaci on two soybean varieties expressing glyphosate resistance and Cry1Ac Bt toxin. These results indicate that some GE soybean varieties expressing insect and herbicide resistances can be more susceptible to whiteflies than non-GE ones or those only expressing herbicide resistance. Most likely, these differences are related to varietal features that increase host-plant susceptibility to whiteflies. Appropriate pest management may be needed to deal with whiteflies in soybean fields, especially in warm regions, and breeders may want to consider the issue when developing new soybean varieties.

BACKGROUND The use of insecticidal solutions containing sodium chloride (NaCl) has been proposed as a more environmentally friendly alternative to managing stink bug infestations of Neotropical soybean fields. The potential sublethal and undesirable effects of this practice have, however, been overlooked, especially with novel insecticides. Here, we have evaluated experimentally whether the addition of NaCl (0.5% w/v) to imidacloprid-containing solutions could alter insecticide toxicity and modify the reproductive responses of the Neotropical brown stink bug Euschistus heros. RESULTS Adding NaCl to imidacloprid solutions significantly increased imidacloprid toxicity against E. heros. The exposure to E. heros to sublethal concentrations of imidacloprid affected the insect's mating abilities in a concentration-dependent manner. The addition of NaCl to solutions containing imidacloprid at concentrations as low as 0.126 μg a.i. cm-2 (i.e. the equivalent to 3% of field rate recommendation) also impacted the sexual behavior of E. heros, reducing mating duration. NaCl-exposed stink bugs, however, exhibited higher fecundity and fertility rates than those insects that were unexposed to NaCl or those that were exposed to sublethal levels of imidacloprid only. CONCLUSIONS The addition of low amounts of NaCl resulted in a higher toxicity of imidacloprid. This practice, however, can also lead to undesirable effects as increasing reproductive output of E. heros that can potentially compromise the management of these insect pests.

The market for biological control of insect pests in the world and in Brazil has grown in recent years due to the unwanted ecological and human health impacts of chemical insecticides. Therefore, research on biological control agents for pest management has also increased. For instance, insect viruses have been used to protect crops and forests around the world for decades. Among insect viruses, the baculoviruses are the most studied and used viral biocontrol agent. More than 700 species of insects have been found to be naturally infected by baculoviruses, with 90% isolated from lepidopteran insects. In this review, some basic aspects of baculovirus infection in vivo and in vitro infection, gene content, viral replication will be discussed. Furthermore, we provide examples of the use of insect viruses for biological pest control and recently characterized baculoviruses in Brazil.

Biorational insecticides are composed of natural products, including animals, plants, microbes, and minerals, or are their derivates. The use of biorational products for the management of insect pests has grown intensively in recent years, which has increased their popularity and share on the insecticide global market. Much of these recent increases in the use of biorational insecticides has been derived from the generalized perception that conventional insecticides have undesirable ecological and human health impacts. However, the idea of simply replacing synthetic compounds with biorational insecticides without considering their potential unintended effects can mislead their use and reduce the market life of such pest management tools. A systematic literature survey encompassing over 15 000 scientific manuscripts published between 1945 and 2019 reinforces the bias of focusing on studying the targeted effects while overlooking the potential detrimental effects of biorational products on human health and the environment (e.g. death and negative sublethal effects on pollinators and beneficial arthropods such as parasitoids and predators). Thus, the risks associated with biorational compounds (e.g. control failures, the evolution of resistance, shift in dominance, and outbreaks of secondary or primary pests) need to be revisited and the outcomes of such inquiry could be decisive for their future use in pest management programs. The shortcomings of regulatory processes, knowledge gaps, and the outlook for the use of the biorational products in pest management are discussed. © 2020 Society of Chemical Industry.

Lygus lineolaris is an important native pest of cotton in the mid-southern USA and a potential invasive species in other parts of the world. L. lineolaris feeds on more than 300 plant species, especially preferring reproductive plant organs but also feeding on young terminal leaves. There is little known about feeding behaviors performed on cotton leaves nor of associated injury symptoms triggered. Herein, we used the most accurate way to study feeding of piercing–sucking insects, i.e., electropenetrography (EPG). EPG was used to quantify L. lineolaris feeding behaviors on young terminal leaves of cotton, for third, fourth, and fifth instars plus male adults. Both non-probing (combined walking, standing and antennation) as well as probing behaviors (cell rupturing, transition, and ingestion) were compared with a time course of digitally measured leaf damage. Overall, L. lineolaris, especially adults, spent most time in non-probing behaviors. For probing behaviors, the longest duration was cell rupturing, especially for fourth and fifth instars followed by the third instars. The greatest damage to cotton leaves occurred when high numbers of wound-inducing cell-rupturing probes, which inject macerating saliva, were combined with minimal subsequent ingestion of saliva. On cotton leaves, this style of cell rupturing matches that of older nymphs. Thus, even small amounts of cell rupture feeding and ingestion by older L. lineolaris nymphs are damaging to cotton leaf terminals. These results help to understand the cause of damage to L. lineolaris hosts and consequently aid in developing strategies to reduce crop loss.

Successful biological control requires detailed knowledge about the mass rearing conditions of the control agents in order to ensure higher quality of field-released insects. Thus, we investigated whether rearing fluctuating thermal condition would affect the fitness and costs of the parasitoid wasp Telenomus podisi Ashmead (a biocontrol agent used for controlling the Neotropical brown stink bug Euschistus heros (Fabricius)) when compared with parasitoid reared at constant temperature condition, which is commonly used in insect facilities. Parasitoids were reared under either constant (continuous exposure at 25 ± 2°C) or fluctuating temperature conditions (i.e., 30 ± 2°C during day and 20 ± 2°C at night) during four consecutive generations. Our results indicated that tested fluctuating temperature is more suitable for rearing of T. podisi as such temperature condition not only resulted in fitness benefits (e.g., shorter developmental time, longer female longevity, higher fecundity/fertility) but also reduced (approximately 23.5%) the estimated costs for producing the parasitoids. Furthermore, rearing T. podisi under fluctuating temperatures improved tolerance to low constant temperatures (i.e., 20°C) without changing the tolerance to constant high temperatures (30°C) in the fourth generation. Surprisingly, even parasitoids that developed under fluctuating thermal conditions performed better than those reared at constant temperature of 25°C. Collectively, our findings suggest that T. podisi reared under fluctuating thermal condition can tolerate better fluctuating temperatures that normally occur both during long periods of transport and in agricultural ecosystems, which will increase the quality and productivity of mass-reared T. podisi for inundative releases.

Pyriproxyfen is a juvenile hormone analogue that is commonly used to control the immature stages of mosquitoes in both artificial and natural water reservoirs. Recently, concerns have been raised regarding the pyriproxyfen community effectiveness in preventing vector-transmitted diseases. Such concerns have been based on the unintended effects on non-target organisms and selection of resistant mosquito populations. Thus, this investigation was conducted aiming to evaluate the toxicity of pyriproxyfen to Aedes aegypti (Diptera: Culicidae) larvae and the backswimmer Buenoa amnigenus (Hemiptera: Notonectidae), a naturally occurring mosquito larvae predator. We also assessed the abilities of backswimmers exposed to sublethal levels of pyriproxyfen to prey upon mosquito larvae (L2) under three larval densities (3, 6, or 9 larvae/100 mL of water) using artificial containers. Our results revealed that pyriproxyfen killed backswimmers only at concentrations higher than 100 mg active ingredient [a.i.]/L, which is 10 times higher than that recommended for larvicidal field application (i.e, 10 mg a.i./L). Interestingly, the abilities of backswimmers exposed to sublethal levels of pyriproxyfen (100 mg a.i./L) to prey upon mosquito larvae were not affected. Harmful effects on the backswimmer predatory abilities were detected only at concentrations of 150 mg a.i./L and when there was a higher prey availability (i.e., 9 larvae/100 mL of water). Together, our findings indicate that the reduced community effectiveness of this insecticide derives from factors other than its detrimental effects on non-target organisms such as the backswimmers.

Chikungunya and Mayaro fevers are viral infectious diseases, without vaccine or treatment, that causes fever and arthralgia. Establishing novel antiviral tools capable of preventing or treating Chikungunya virus (CHIKV), and Mayaro virus (MAYV) infections are needed. The use of plant-based compounds that affect the replication cycles of these viruses has been proposed as a promising strategy. Chiococca alba (L.) Hitchc. is a neotropical plant used by Yucatec Mayas traditional healers, mainly, as antipyretic and antirheumatic. To evaluate the potential of C. alba methanolic extracts against CHIKV and MAYV through preliminary analysis in vitro and in silico. The cytotoxicity profile of two C. alba roots methanolic extracts in Vero cells was performed by lysosomal viability using the neutral red assay, and the antiviral potential was determined by plaque assay. We further assessed, through in silico computational predictions, the possible interactions between the active site of the nsP2 proteases of these viruses with some secondary metabolites present in C. alba extracts, identified by High-Performance Liquid Chromatography (HPLC). Our partial phytochemical analysis revealed the presence of flavonoids, and phenolic acids in the C. alba extracts. Our in vitro assays showed that both C. alba extracts inhibited more than 70% of CHIKV and MAYV activities at 60 µg/mL concentration. Based on our in silico computational predictions, the flavonoids naringin and vitexin showed the greatest affinity energies with the CHIKV and MAYV nsP2 proteases, revealing the great potential of these compounds as viral inhibitors. The findings described here indicates that C. alba extracts, or their secondary metabolites, as a potential source of novel antiviral compounds.

The spittlebugs Mahanarva spectabilis economically challenges cattle production of neotropical regions, due to its voracious feeding on tropical grasses. Here, we evaluated biochemical responses of the interaction between M. spectabilis and the widely cultivated tropical grasses Brachiaria spp. (i.e., brizantha and decumbens) and elephant grasses (cvs. Roxo de Botucatu and Pioneiro), regarding lipoxygenases, protease inhibitors, phytohormones, and proteolytic activities in the midgut of M. spectabilis. The M. spectabilis-infested grasses increased lipoxygenases activity, except for cv. Pioneiro. The levels of the phytohormones jasmonic and abscisic acids were similarly low in all genotypes and increased under herbivory. Furthermore, salicylic acid concentration was constitutively higher in Brachiaria sp., increasing only in spittlebug-infested B. decumbens. M. spectabilis infestations did not induce increases of protease inhibitors in any forage grass type. The trypsin activity remained unaltered, and the total proteolytic activity increased only in B decumbens-fed insects. Our findings revealed that most forage grasses exposed to spittlebugs activate the lipoxygenases pathway, resulting in increased abscisic and jasmonic acids. However, greater amounts of these hormones do not induce protease inhibitory activity in response to spittlebug attack. This knowledge certainly helps to guide future projects aiming at reducing the impact of spittlebugs on forage production. Made available in DSpace on 2021-09-15T12:00:27Z (GMT). No. of bitstreams: 1 Differential-defense.pdf: 966114 bytes, checksum: 1aff97283378e2d95870009591ee6794 (MD5) Previous issue date: 2021

RNA interference (RNAi)-based pesticides are promising novel pest management products that might reduce environmental impacts compared to other pesticides. Their sequence-guided mode of action facilitates a high species-selectivity, preventing harm on non-target organisms. However, there is currently no consensus on the minimum needed sequence similarity for efficient RNAi in insects and studies have shown that adverse effects in non-targets cannot always be ruled out a priori. This study investigates the effects of exposing the parasitoid wasp Telenomus podisi to double-stranded RNA (dsRNA) which is lethal to its host, the Neotropical brown stink bug Euschistus heros. Feeding T. podisi with wasp-specific dsRNA targeting the vATPase A and actin-2 genes led to 76.4 ± 9.9% and 76.7 ± 8.8% mortality respectively, demonstrating that dietary RNAi is functional in T. podisi. When feeding T. podisi with E. heros-specific dsRNA targeting the same genes, no lethal or sublethal effects were observed. To link sequence similarity to potential gene silencing effects in the parasitoids, the expression of genes showing the highest degree of similarity (17-21 nucleotide matches) with these two target genes was monitored and was found unaffected by the E. heros-specific dsRNA. Our study confirms that RNAi was in this case highly specific and that for E. heros, RNAi-based pesticides can be used complementary to biological control in an integrated pest management context.

Pyrethrum extract from dry flowers of Tanacetum cinerariifolium (formally Chrysanthemum cinerariifolium) has been used globally as a popular insect repellent against arthropod pests for thousands of years. However, the mechanistic basis of pyrethrum repellency remains unknown. In this study, we found that pyrethrum spatially repels and activates olfactory responses in Drosophila melanogaster, a genetically tractable model insect, and the closely-related D. suzukii which is a serious invasive fruit crop pest. The discovery of spatial pyrethrum repellency and olfactory response to pyrethrum in D. melanogaster facilitated our identification of four odorant receptors, Or7a, Or42b, Or59b and Or98a that are responsive to pyrethrum. Further analysis showed that the first three Ors are activated by pyrethrins, the major insecticidal components in pyrethrum, whereas Or98a is activated by (E)-β-farnesene (EBF), a sesquiterpene and a minor component in pyrethrum. Importantly, knockout of Or7a, Or59b or Or98a individually abolished fly avoidance to pyrethrum, while knockout of Or42b had no effect, demonstrating that simultaneous activation of Or7a, Or59b and Or98a is required for pyrethrum repellency in D. melanogaster. Our study provides insights into the molecular basis of repellency of one of the most ancient and globally used insect repellents. Identification of pyrethrum-responsive Ors opens the door to develop new synthetic insect repellent mixtures that are highly effective and broad-spectrum., Author summary Pyrethrum extract began to be used as an insect repellent against biting arthropods and blood-sucking mosquitoes since ancient times. However, the mechanisms underlying pyrethrum repellency remains unknown. In this study, we took advantage of Drosophila melanogaster as a model insect system for olfaction studies and conducted a series of electrophysiological, molecular genetic and behavioral experiments to understand the mechanism of pyrethrum repellency in D. melanogaster. We discovered that pyrethrum repels D. melanogaster by activating multiple odorant receptors (Ors). Apparently simultaneous activation of these Ors by various components in pyrethrum extract makes pyrethrum one of the most potent and the longest used insect repellents in the human history.

Many environmental stressors are currently implicated in the decline of flying insects in general, and important pollinator species such as the honey bee. Recent studies have shown that extremely low frequency electromagnetic fields (ELF EMFs) affect many aspects of insect behaviour and cognition which raises the potential that ELF EMFs could interact with other environmental stressors such as neonicotinoid insecticides to have even greater impact on the decline of flying insects. Here we analysed the effects of individual and combined exposure of the honey bee to 50 Hz EMFs and sublethal exposure to clothianidin, in a tethered flight assay and an olfactory appetitive learning assay. Clothianidin was significantly toxic to bees and exposure to field-realistic levels (2.00 ng/bee) led to 25% mortality. Exposure to ELF EMFs alone led to a significant increase in wingbeat frequency at levels above 100 µT. Prior exposure to clothianidin attenuated the effects of EMFs on wingbeat frequency. Exposure to EMFs alone reduced learning of a proboscis extension reflex (PER). Prior exposure to low doses of clothianidin attenuated the effects of EMFs on PER. These results indicate no evidence of synergy between clothianidin and ELF EMFs as environmental stressors but suggest the potential for EMFs to affect the same susceptible fraction of the bee population that have been affected by clothianidin. Results lay the foundation to further explore the interactions of ELF EMFs with other environmental stressors and consider the key factors that may make bees susceptible to ELF EMFs.

Background Volatile pyrethroid insecticides, such as transfluthrin, have received increasing attention for their potent repellent activities in recent years for controlling human disease vectors. It has been long understood that pyrethroids kill insects by promoting activation and inhibiting inactivation of voltage-gated sodium channels. However, the mechanism of pyrethroid repellency remains poorly understood and controversial. Methodology/Principal findings Here, we show that transfluthrin repels Aedes aegypti in a hand-in-cage assay at nonlethal concentrations as low as 1 ppm. Contrary to a previous report, transfluthrin does not elicit any electroantennogram (EAG) responses, indicating that it does not activate olfactory receptor neurons (ORNs). The 1S-cis isomer of transfluthrin, which does not activate sodium channels, does not elicit repellency. Mutations in the sodium channel gene that reduce the potency of transfluthrin on sodium channels decrease transfluthrin repellency but do not affect repellency by DEET. Furthermore, transfluthrin enhances DEET repellency. Conclusions/Significance These results provide a surprising example that sodium channel activation alone is sufficient to potently repel mosquitoes. Our findings of sodium channel activation as the principal mechanism of transfluthrin repellency and potentiation of DEET repellency have broad implications in future development of a new generation of dual-target repellent formulations to more effectively repel a variety of human disease vectors., Author summary Vector-transmitted human diseases, such as dengue fever, represent serious global health burdens. Pyrethroids, including transfluthrin, are widely used as insecticides and repellents due to their low mammalian toxicity and relatively benign environmental impact. Pyrethroids target voltage-gated sodium channels for their insecticidal action. However, the mechanism of pyrethroid repellency remains unclear and controversial. Insect repellency is traditionally thought to be mediated by olfactory receptors. We made two important discoveries in this study, showing that transfluthrin repellency is via activation of sodium channels and transfluthrin enhances DEET repellency. Discovery of sodium channel activation as a major mechanism of pyrethroid repellency has broad significance in insect olfaction study, repellents development, and control of human disease vectors.

Background Using plant-based extracts and their constituents has been suggested as alternative tools to replace or integrate with the synthetic compounds used to manage insect pests. Here, we evaluated the potential of extracts obtained from Ficus carica Linn (Moraceae) branches and leaves against the Neotropical brown stink bug, Euschistus heros, one of the most prevalent insect pests in soybean fields. We further isolated and evaluated the toxicity of the extracts' major components against E. heros. Additionally, by using computational docking analysis and toxicological approaches, we assessed the physiological basis for the selectivity of these extracts against beneficial insects such as pollinator bees (i.e., Apis mellifera and the Neotropical stingless bee Partamona helleri), ladybeetles (Eriopis connexa and Coleomegilla maculata), and lacewings (Chrysoperla externa). Results Our results demonstrated that branch (LC50 = 5.9 [4.7-7.1] mg/mL) and leaf (LC50 = 14.1 [12.5-15.4] mg/mL) extracts exhibited similar toxicity against E. heros. Our phytochemical analysis revealed psoralen and bergapten furanocoumarins as the major components of the extract. Based on our computational predictions, these molecules' differential abilities to physically interact with the acetylcholinesterases of E. heros and beneficial insects play relevant roles in their selectivity actions. The estimated LC90 values of branch (30.0 mg/mL) and leaf (30.0 mg/mL) extracts killed less than 12% of the beneficial insects. Conclusion Overall, our findings revealed that furanocoumarin-rich extracts obtained from F. carica extracts have the potential to be used as alternative tools in the integrated management of stink bug pests. This article is protected by copyright. All rights reserved.

Pesticide effects on natural enemies in an agroecosystem are of paramount importance for integrated pest management programs. Natural enemies can be subject to direct and indirect exposure to insecticides and synergistic molecules (e.g., sodium chloride - NaCl) which are used to control various pests of agricultural crops such as soybean. Here, we evaluated the potential effects of imidacloprid and its interaction with NaCl as an enhancer on the survival and reproductive abilities of the non-target predator Podisus nigrispinus (Dallas) (Hemiptera: Pentatomidae). The insects were exposed to the stink bugs control field recommended dose of imidacloprid associated or not with the salt at the concentration of 0.5% (w/v). NaCl as a pesticide enhancer did not affect the survival of P. nigrispinus adults after 48 h of exposure (less than 12% of mortality was always recorded). However, the fifth instar nymph mortality was almost 50%. The effects of imidacloprid on the reproductive parameters of P. nigrispinus included a decrease in the oviposition, showing fewer eggs per day. However, the fertility was not affected. The NaCl addition, therefore, had no effect on the mortality, survival, and reproduction of the non-target predator. The use of NaCl associated to imidacloprid and other pesticides in the presence of P. nigrispinus demonstrated compatibility, however, it requires further evaluation to endorse the set of these pest control strategies. Resumen Los efectos de los pesticidas sobre los enemigos naturales en un agroecosistema son de suma importancia para los programas de manejo integrado de plagas. Los enemigos naturales pueden estar sujetos a la exposición directa e indirecta de insecticidas y moléculas sinérgicas (por ejemplo, cloruro de sodio - NaCl) que se utilizan para controlar diversas plagas de cultivos agrícolas como la soja. Aquí, evaluamos los posibles efectos del imidacloprid y su interacción con NaCl como un potenciador de la supervivencia y las capacidades reproductivas del depredador no objetivo Podisus nigrispinus (Dallas) (Hemiptera: Pentatomidae Los insectos fueron expuestos a una tasa de campo de imidacloprid, recomendado para controlar los chinches en campos de soya. La solución de imidacloprid fue mezclada (o no) con NaCl (0.5%, w/v). El NaCl como potenciador de pesticidas no afectó la supervivencia de los adultos de P. nigrispinus después de 48 h de exposición (siempre se registró menos del 12% de mortalidad). Sin embargo, la mortalidad de la ninfa del quinto estadio fue casi del 50%. Los efectos de imidacloprid sobre los parámetros reproductivos de P. nigrispinus incluyeron una disminución en la oviposición, mostrando menos huevos por día. Sin embargo, la fertilidad no se vio afectada. La adición de NaCl, por lo tanto, no tuvo efecto sobre la mortalidad, supervivencia y reproducción del depredador no objetivo. El uso de NaCl asociado a imidacloprid y otros pesticidas en presencia de P. nigrispinus demostró compatibilidad, sin embargo, requiere una evaluación adicional para respaldar el conjunto de estas estrategias de control de plagas.

The application of agrochemicals plays a key role in the world's food and agricultural products supply. Brazil, as one of the most relevant agricultural global players is highly dependent on the application of such products, which surely attracted not only companies that licitly commercialized the pesticides but also the so termed pesticide smugglers. Here, we conducted a retrospective survey (i.e., from 2010 to 2017) regarding the apprehension of illegal products, agricultural productivity and food poisoning in the state of Mato Grosso do Sul (MS). The statistical data were obtained by official agencies Such as Technical-Scientific Sector of the Federal Police Department of the MS State, The System of Control of Seized Goods, The National Toxic-Pharmacological Information System and The Brazilian Institute of Geography and Statistics, and by the non-official National Union of the Product Industry for Plant Protection agency. The results indicated that in 2011 the MS state had the largest number of seizures of illegal pesticides compared to other years. In addition, from 2010 to 2013, the state was among the regions with the highest number of seizures. In the same period, the agricultural productivity of the cotton, sugarcane, corn and soybean crops was lower compared to the other years. Regarding the food poisoning, the percentage of human intoxication by agrochemicals for agricultural use was low compared to all cases of intoxication by various toxic agents. It was concluded that the state MS presented a large amount of seizure of illegal pesticides.

BACKGROUND: The application of lime sulfur is a common practice used to control arthropod pests in organic production of fruits. However, the unintended effects of this insecticide preparation on non‐targeted organisms have not received the adequate attention. Here, we evaluated the lime sulfur toxicity on the phytophagous mites Tetranychus urticae Koch (Acari: Tetranychidae) and on two predatory mite species [i.e., Neoseiulus californicus (McGregor) and Phytoseiulus macropilis (Banks)] (Acari: Phytoseiidae) of natural occurrence in strawberry plants. We also assessed the repellency and potential effects on the oviposition rates and the egg viability of mites that were exposed to field‐used lime sulfur concentrations (i.e., 2%). RESULTS: The lime sulfur exhibited higher toxicity to the predators N. californicus (LC₅₀ = 5.4 [4.5%–6.8%]) and P. macropilis (LC₅₀ = 5.0 [4.0%–6.5%]) than to the phytophagous T. urticae (LC₅₀ = 12.4 [9.0%–17.1%]). However, the exposure to field‐applied concentrations resulted in higher reductions on the oviposition rate of T. urticae (36%) than on the predatory mites (N. californicus = 18%. P. macropilis = 19%). Interestingly, although the egg viability of P. macropilis was less affected (i.e., reduction of 50%) by such lime sulfur exposures, these mites were unable to avoid lime sulfur‐treated areas. Egg viability of N. californicus was only 18.6%. CONCLUSION: Lime sulfur at field‐applied concentrations harmed T. urticae fecundity and fertility and it showed selectivity against naturally occurring predatory mites, which reinforces its potential as a tool for integrated mite pest management. © 2019 Society of Chemical Industry

The ecological and economic contributions of pollinator bees to agricultural production have been threatened by the inappropriate and excessive use of pesticides. These pesticides are often applied in areas with ecological peculiarities (e.g., the Neotropical savannah-like region termed as Cerrado) that were not considered during the product development. Here, we conducted field experiments with melon (i.e., Cucumis melo L.) plants cultivated under Brazilian Cerrado conditions and evaluated the impacts of botanical (i.e., neem-based insecticide) and synthetic (i.e., the pyrethroid insecticide deltamethrin and the fungicides thiophanate-methyl and chlorothalonil) pesticides on the flower visitation rates of naturally occurring pollinator bees. Our results revealed that both honey bees (i.e., Apis mellifera L.) and non-Apis bees visited melon flowers and the intensity of bee visitation was moderately correlated with yield parameters (e.g., number of marketable fruits and fruit yield). Pesticide treatments differentially affected bee species. For instance, Plebeia sp. bees were not affected by any pesticide treatment, whereas both A. mellifera and Halictus sp. bees showed reduced visitation intensity after the application of deltamethrin or neem-based insecticides. Fungicide treatment alone did not influence the bee's visitation intensity. Deltamethrin-treated melon fields produced significantly lighter marketable fruits, and the melon yield was significantly lower in melon fields treated with the neem-based insecticide. Thus, our findings with such pollinator bees reinforce the idea that field applications of botanical pesticides may represent as risky as the applications of synthetic compounds, indicating that these alternative products should be submitted to risk assessments comparable to those required for synthetic products.

The protection of stored products from insect damages, when accomplished, is mostly relying on the application of synthetic insecticides with serious health and environmental issues in addition to risks of selection of resistant insect populations associated with such practice. The use of plants derived compounds have been presented as sound strategy for sustainable insect pest management. Eugenol is an aromatic component of natural occurrence in essential oils of numerous plants. known for its repellent and insecticidal bioactivities against different insect species. Here, we investigated the fumigant application of eugenol to control the cowpea weevil Callosobruchus maculatus (Coleoptera: Chrysomelidae: Bruchinae) by assessing toxicity, effects on biological development (including emergence inhibition) and repellency to these weevil. Besides a good fumigant insecticidal activity, eugenol exposure resulted in a dose-dependent decrease of the growth rate of C. maculatus associated with a steady reduction in bean mass losses. Additionally, inhibition of offspring was upper 50% when adults were exposed to lethal and sublethal concentrations. significant inhibition of the offspring emergence was achieved after the exposure of parental adults to lethal and sublethal doses of eugenol. Furthermore, adult weevils were repelled away from beans exposed to high dose (LD99) of eugenol in contrast with their attraction to the beans treated with lower dose (LD50). Our findings suggest that eugenol has potential as control tool to be used in sustainable management startegies of C. maculatus.

The use of wood residues and their extracts as sources for bioactive molecules not only helps to reduce the environmental impacts of the wastage produced by timber industry but also provide innumerous biotechnological application opportunities, including the development of novel insecticide products. Here, the insecticidal and repellent (in gel and cream formulations) potential of wood extracts of the Neotropical plant “purple ipe”, Tabebuia heptaphylla (Bignoniaceae) against the mosquitoes Aedes aegypti are investigated. Firstly, the chemical composition of the chloroform and hexane extracts obtained from T. heptaphylla residues is analyzed and their insecticidal activities are assessed against A. aegypti larvae. Furthermore, the repellence and oviposition deterrence actions of these extracts were evaluated against adult mosquito females. Computational docking analysis was also conducted to predict the physical interactions between the major constituents of the T. heptaphylla residue extracts and the odorant binding receptor of A. aegypti. Despite the fact that the 2,6-di-tert-butylnaphthalene was the major constituent (53.3%) in the T. heptaphylla hexanoic extract, the presence of lapachol, 2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthalenedione, as major constituent in both wood extracts combined with the computational docking analysis, strongly suggest the lapachol as the major factor of the insecticidal/repellent effects of T. heptaphylla wood extracts. The computational docking analysis predicted significant binding of lapachol with the internal active pocket of the mosquito odorant binding receptor, which helps to explain the up to 3 h protection against bites of A. aegypti females provided by gel and cream formulations containing the T. heptaphylla residue extracts. Collectively, the findings demonstrated relevant biotechnological and environmentally-friend opportunities (i.e., production of biopesticides) for the wood residues produced by timber activities during the extraction and processing of T. heptaphylla trees.

Sublethal exposure to insecticides can trigger unintended responses in non-target insects that may disrupt reproductive and developmental performances of these organisms. Here, we assessed whether sublethal exposure to the pyrethroid insecticide deltamethrin in early life had sublethal and transgenerational effects on the reproduction (i.e., fecundity and fertility) and wing morphology of Chironomus columbiensis, an aquatic insect used as a water quality indicator. We first conducted concentration-response bioassays to evaluate the susceptibility of C. columbiensis larvae to deltamethrin. Our results revealed that deltamethrin toxicity was approximately 7-fold higher when C. columbiensis larvae where exposed to 96 h (LC

Biological invasions have reached large parts of the globe, due to human actions across the planet. Drosophila suzukii (Matsumura, 1931) is a globally invasive species, always associated with enormous and costly damage to agricultural crops. Native to Southeast Asia, D. suzukii recently (i.e., 2013) invaded and is dispersing through South America. Here, we used a phylogeographic approach based on the cytochrome c oxidase subunit I gene fragment to explore the invasion dynamics of D. suzukii populations in Brazil. We identified five haplotypes and moderate genetic diversity in Brazilian populations, which are undergoing demographic and spatial expansion. The analyses of molecular variance indicated a high genetic structure among the populations, which is partially explained by their morphoclimatic origin and invasion history. Drosophila suzukii expanded from southern to southeastern Brazil, aided by human-mediated transport of fruits from region to region. The sharing of haplotypes among Brazilian and other invaded regions of the world suggests a single invasion event of D. suzukii in Brazil, originating from previously invaded areas (e.g., North America and Europe). The rapid geographic dispersal and wide variety of fruits attacked by of D. suzukii require immediate implementation of control strategies (legal and phytosanitary) to manage this pest in Brazil.

Target-site mutations and changes in insect metabolism or behavior are common mechanisms in insecticide-resistant insects. The co-occurrence of such mechanisms in a pest strain is a prominent threat to their management, particularly when alternative compounds are scarce. Pyrethroid resistance among stored grain weevils (i.e., Sitophilus spp.) is an example of a long-standing concern, for which reports of resistance generally focus on a single mechanism in a single species. Here, we investigated pyrethroid resistance in maize and rice weevils (i.e., Sitophilus zeamais and S. oryzae), exploring potential knockdown resistance (kdr) mutations in their sodium channels (primary site for pyrethroid actions) and potential changes in their detoxification and walking processes. Resistance in pyrethroid-resistant rice weevils was associated with the combination of a kdr mutation (L1014F) and increases in walking and detoxification activities, while another kdr mutation (T929I) combined with increases in walking activity were the primary pyrethroid resistance mechanisms in maize weevils. Our results suggest that the selection of pyrethroid-resistant individuals in these weevil species may result from multiple and differential mechanisms because the L1014F mutation was only detected in Latin American rice weevils (e.g., Brazil, Argentina and Uruguay), not in Australian and Turkish rice weevils or Brazilian maize weevils.

Despite being effective in controlling mosquito larvae and a few other target organisms, the application of insecticides into aquatic systems may cause unintended alterations to the physiology or behavioral responses of several aquatic non-target organisms, which can ultimately lead to their death. Here, we firstly evaluated whether the susceptibility of the giant water bug, Belostoma anurum (Hemiptera: Belostomatidae), a predator of mosquito larvae, to pyriproxyfen would be similar to that of its potential prey, larvae of Aedes aegypti (Diptera: Culicidae). Secondly, we recorded the nominal concentrations of pyriproxyfen in water and evaluated whether sublethal exposures would lead to physiological or behavioral alterations on the B. anurum nymphs. We characterized the activities of three major families of detoxification enzymes (i.e., cytochrome P450 monooxygenases, glutathione-S-transferase, and general esterases) and further evaluated the abilities of pyriproxyfen sublethally-exposed B. anurum to prey upon A. aegypti larvae at different prey densities. Our findings revealed that nominal pyriproxyfen concentration significantly decreased (approximately 50%) over the first 24 h. Furthermore, when applied at the concentration of 10 μg a.i./L, pyriproxyfen was approximately four times more toxic to A. aegypti larvae (LT50 = 48 h) than to B. anurum nymphs (LT50 = 192 h). Interestingly, the pyriproxyfen sublethally-exposed (2.5 μg a.i./L) B. anurum nymphs exhibited reduced enzyme activities (cytochrome P450 monooxygenases) involved in detoxication processes and preyed significantly less on A. aegypti larvae when compared to unexposed predators. Collectively, our findings demonstrate that mortality-based pyriproxyfen risk assessments are not always protective of aquatic non-target organisms.

Stingless bees such as Partamona helleri Friese play important roles in pollination of native plants and agricultural crops in the Neotropics. Global concerns about declining bee populations due to agrochemical pollutants have, however, been biased towards the honey bee, Apis mellifera Linnaeus. Here, we analysed the unintended effects of commercial formulations of a neonicotinoid insecticide, imidacloprid, and a fungicide mixture of thiophanate-methyl and chlorothalonil on color preference, respiration rates and group locomotory activities of both P. helleri and A. mellifera. Our results revealed that P. helleri foragers that were not exposed to pesticides changed their color preference during the course of a year. By contrast, we found that pesticide exposure altered the color preference of stingless bees in a concentration-dependent manner. In addition, imidacloprid decreased the overall locomotion of both bee species, whereas the fungicide mixture increased locomotion of only stingless bees. The fungicide mixture also reduced respiration rates of forager bees of both species. Forager bees of both species altered their color preference, but not their locomotory and respiration rates, when exposed to commercial formulations of each fungicidal mixture component (i.e., chlorothalonil and thiophanate-methyl). Our findings emphasize the importance of P. helleri as a model for Neotropical wild pollinator species in pesticide risk assessments, and also the critical importance of including groups of agrochemicals that are often considered to have minimal impact on pollinators, such as fungicides.

Pyrethrum extracts from flower heads of Chrysanthemum spp. have been used worldwide in insecticides and repellents. While the molecular mechanisms of its insecticidal action are known, the molecular basis of pyrethrum repellency remains a mystery. In this study, we find that the principal components of pyrethrum, pyrethrins, and a minor component, (E)-β-farnesene (EBF), each activate a specific type of olfactory receptor neurons in Aedes aegypti mosquitoes. We identify Ae. aegypti odorant receptor 31 (AaOr31) as a cognate Or for EBF and find that Or31-mediated repellency is significantly synergized by pyrethrin-induced activation of voltage-gated sodium channels. Thus, pyrethrum exerts spatial repellency through a novel, dual-target mechanism. Elucidation of this two-target mechanism may have potential implications in the design and development of a new generation of synthetic repellents against major mosquito vectors of infectious diseases., Although pyrethrum is used to repel insects for centuries, the underlying mechanism has been enigmatic. Liu et al. found that specific components of pyrethrum mediate repellency by targeting olfactory receptors and/or voltage-gated sodium channels in Aedes aegypti mosquitoes.

Bacillus thuringiensis serovar israelensis (Bti) is used to control insect vectors of human and animal diseases. In the present study, the toxicity of four strains of Bti, named T0124, T0131, T0137, and T0139, toward Aedes aegypti and Culex quinquefasciatus larvae was analyzed. The T0131 strain showed the highest larvicidal activity against A. aegypti (LC50 = 0.015 µg/ml) and C. quinquefasciatus larvae (LC50 = 0.035 µg/ml) when compared to the other strains. Furthermore, the genomic sequences of the four strains were obtained and compared. These Bti strains had chromosomes sizes of approximately 5.4 Mb with GC contents of ~35% and 5472–5477 putative coding regions. Three small plasmids (5.4, 6.8, and 7.6 kb) and three large plasmids (127, 235, and 359 kb) were found in the extrachromosomal content of all four strains. The SNP-based phylogeny revealed close relationship among isolates from this study and other Bti isolates, and SNPs analysis of the plasmids 127 kb did not reveal any mutations in δ-endotoxins genes. This newly acquired sequence data for these Bti strains may be useful in the search for novel insecticidal toxins to improve existing ones or develop new strategies for the biological control of important insect vectors of human and animal diseases.

The adaptive fitness of insect species can be shaped by how males and females respond, both physiologically and behaviorally, to environmental challenges, such as pesticide exposure. In parasitoid wasps, most toxicological investigations focus only on female responses (e.g., survival and especially parasitism abilities), leaving the male contributions to adaptive fitness (survival, locomotion, mate search) poorly investigated. Here, we evaluated the toxicity of the spinosyn insecticide spinosad against the South American fruit fly, Anastrepha fraterculus, and we used the parasitoid wasp Diachasmimorpha longicaudata (Ashmead) to evaluate whether sex-linked locomotory and physiological responses would influence the susceptibility of these organisms to spinosad. Our results revealed that D. longicaudata males were significantly more susceptible (median lethal time (LT50) = 24 h) to spinosad than D. longicaudata females (LT50 = 120 h), which may reflect the differences in their locomotory and physiological (e.g., respiratory) responses to mitigate insecticide exposure. Compared to D. longicaudata females, male wasps were lighter (P

Neonicotinoid insecticides (e.g., imidacloprid) are some of the most prevalent tools used to control hemipterans that attack soybean crops worldwide. However, the emergence of neonicotinoid-resistant strains of phytosuccivorous soybean pests, such as the Neotropical brown stink bug Euschistus heros, has posed a challenge to the sustainable use of these compounds. Here, we laboratory-selected two E. heros strains for imidacloprid resistance and evaluated the activity of detoxification enzymes (e.g., cytochrome P450, esterases and glutathione-S-transferases) as well as potential adaptive costs associated with resistance (e.g., in survival, fecundity and fertility) in both strains, while laboratory selection for 13 generations in a known imidacloprid-susceptible E. heros strain (ImiSusc) resulted in an imidacloprid-resistant strain (ImiLabSel) with a resistance ratio (RR) of 11.6; similar resistance levels (i.e., RR = 13.5) were also achieved in another imidacloprid-resistant strain, which was field-collected (ImiGoias) and laboratory-selected for only six generations (ImiRes). Regarding enzymatic activity, both resistant strains differed from the imidacloprid-susceptible strain only in the activity of cytochrome P450, where the ImiLabSel and ImiRes strains exhibited higher activity by 72.3% and 40.5%, respectively. Furthermore, severe fitness costs (reductions of 86% for ImiLabSel and 68.0% for ImiRes) were recorded in both imidacloprid-resistant strains. Collectively, our results showed that E. heros rapidly responded to laboratory selection for neonicotinoid resistance, with enhanced cytochrome P450 activity as the likely underlying mechanism, and that they exhibit associated fitness costs, which have direct implications for the management of this insect pest.