Toxic Baits Research Articles

Balancing act: evaluating non-target risks of feral cat management in conservation reserves

Context Predation by feral cats continues to place substantial pressure on native Australian wildlife, contributing to significant population declines and localised extirpations of susceptible species. In Western Australia (WA), the registration of the poison bait Eradicat® provides a tool to help manage these introduced predators, but only in areas where the risk to non-target species is considered acceptable. The red-tailed phascogale (Phascogale calura), a small carnivorous marsupial now restricted to vegetation remnants in the highly fragmented agricultural zone of south-western WA (i.e. the Wheatbelt), is one species that may be vulnerable to lethal ingestion. Aim To investigate the impact of repeated Eradicat® baiting, to control feral cats, on the activity levels of the red-tailed phascogale, focusing on populations in two Wheatbelt conservation reserves. Methods We established a novel approach to monitoring red-tailed phascogales by using tree-mounted camera trap arrays in an area with feral cat management using ground-delivered Eradicat® baits, and two control zones with no feral cat management. We examined changes in activity levels (detection rate and occupancy) based on camera trap detections, before and after Eradicat® application, across two autumn and two spring baiting events. We also investigated non-target bait uptake using camera traps. Key results Although a small number of baits (7/60) was removed by red-tailed phascogales from the field of view of a camera, our results showed no overall impact of Eradicat® on their activity levels within the study area. Tree-mounted camera traps proved to be highly effective and efficient at detecting red-tailed phascogales. To maximise camera detections, the optimal time for monitoring red-tailed phascogales is during autumn, prior to male die-off. Conclusions Our results suggested that the risk posed to red-tailed phascogale populations from the repeated use of Eradicat® baits is likely to be low. Implications Integrating the application of Eradicat® to control feral cats with existing fox control in conservation reserves that support populations of red-tailed phascogales is likely to pose minimal risk to the species.

An overview of the development of termite baits in the past 3 decades.

Since the commercialization in 1995, termite baits have been introduced in 32 countries, protecting over 3.7 million homes and reducing pesticide use by more than 11,100 metric tons. Over the past 3 decades, advancements have been made to address the limitations of bait systems, including improvements in bait toxicants, bait matrices, and the frequency of required site visits. Termite baits have been applied in both commercial and experimental area-wide projects. This article discusses the factors contributing to the success of these projects and the key elements driving the progress and advancements in termite bait technology.

A study on the effectiveness of (+)-usnic acid as oral toxic sugar bait against adult male and female Anopheles gambiae

BackgroundDespite the application of various tools for the control of vectors of Plasmodium falciparum, malaria remains the major killer disease in sub-Saharan Africa accounting for up to 90% of deaths due to the disease. Due to limitations of the useage of chemical insecticides such as resistance, negative impact on the environment and to nontarget organisms, the World Health Organization (WHO) requires that affected countries find alternative vector control tools. This study evaluated the effectiveness of ( +)-usnic acid (UA) as an insecticide through oral administration to male and female Anopheles gambiae as an alternative or additional active ingredient to be used in toxic sugar bait.Methods( +)-usnic acid was diluted using acetone at 5, 10, and 15 mg/ml concentrations in three replicates. A 5 ml mixture of 2% food dye and 10% sugar using chlorine-free water mixed with the dilutions of the ( +)-usnic acid and negative control was made containing 2% food dye and 10% sugar solution. The preparations were soaked on a ball of cotton wool and placed over the net of a cup. 5 male and 5 non-blood-fed female newly hatched starved An. gambiae Kisumu strain were introduced together into a cup and monitored for knockdown and mortalities after 4, 24 48, and 72 h. The data were analysed using a multiple linear regression model using the lm function, a base R function and a posthoc test were conducted on the significant main effects and interaction terms using the emmeans function from the emmeans R package. All analyses were performed in RStudio using base R (version 4.3.3).ResultsThere was high mortality of both male and female An. gambiae after ingestion of the toxic sugar bait. 15 mg/ml usnic acid caused the highest mortality (50%) within the first 4 h compared to 5 and 10 mg/ml ( +)-UA. There was a decline in the mortality rate with increased exposure time from 24 to 72 h, however, there was a significant difference in mortality at 5, 10 and 15 mg/ml. Acute toxicity was associated with ingestion of 15 mg/ml after 24 h. 72 h post-mortality was lower in all concentrations than in the control. High mortality was observed among females over the first 4 h (60%) compared to males (40%) due to higher feeding rate of the toxic agent. The proportion of dead males and females was equal after 24 h while after 48 h, the proportion of dead males was high.There was a significantly lower mortality rate after 72 h for both males and females (0 to 13.3%). Compared to all the treatments, high mortality of males was observed.ConclusionsThe results of this study indicate that ( +)-UA when administered as oral sugar bait to An. gambiae has insecticidal properties and is a suitable ingredient to be used as a toxic agent in the novel attractive toxic sugar bait for the control of malaria vectors. ( +)-UA may be an alternative active ingredient as toxic bait in the effort to reduce and eliminate the transmission of Plasmodium falciparum in Africa.

Preference and Toxicity of Sulfoxaflor, Flupyradifurone, and Triflumezopyrim Bait against the Fire Ant Solenopsis invicta (Hymenoptera: Formicidae) and Their Efficacy under Field Conditions.

The red imported fire ant Solenopsis invicta Buren (Hymenoptera: Formicidae) is native to South America; however, its introduction to other countries has caused serious biodiversity, agricultural, and public health problems. As toxic bait is an effective method to control fire ant populations, the aim of this study was to determine the most effective concentration of sulfoxaflor, flupyradifurone, and triflumezopyrim as ingredients for baits against S. invicta under laboratory and field conditions. Sulfoxaflor, flupyradifurone, and triflumezopyrim had no effect on the feeding behavior of the fire ants. However, they significantly reduced the climbing, walking, and arrest abilities of the fire ant workers after 10 days of treatment, and insecticides were horizontally transferred from workers to alates or larvae. Specifically, sulfoxaflor and triflumezopyrim at 0.05% concentration were the most effective in exterminating fire ants. Sulfoxaflor and triflumezopyrim are nonrepellent and effective insecticides against S. invicta.

Sugar feeding in triatomines: a new perspective for controlling the transmission of Chagas disease.

Introduction: Triatomines are vectors of Trypanosoma cruzi, the etiological agent of Chagas disease. Currently, there is no vaccine against this disease. Thus, control of the insect vector population is the main strategy available to reduce the number of cases. Triatomines are considered obligate hematophagous, but different alternative feeding behaviors were described, such as haemolymphagy or plant feeding. Methods: To determine the preference for sugar feeding in nymphs and adults of Rhodnius prolixus, the insects were exposed a piece of cotton containing bromophenol blue plus sucrose. In addition, we offered several sugars for different species of triatomines, and tested sugar meals as a route of delivery of insecticides in first-instar nymphs of R. prolixus. The effect of sugar feeding on the physiology of these different species of triatomines was recorded. Results: First instar nymphs ingested sucrose more strongly than other stages, and showed high mortality rates. In different species of triatomines, sucrose induced an ingestion, but engorgement varied according to the species. R. prolixus nymphs showed an indiscriminate intake of various sugars, with very different physiological effects. Furthermore, ingesting different combinations of insecticides + sugar significantly reduced insect survival. Discussion: In summary, we described for the first-time sugar feeding as a widespread behavior in several species of triatomines, and the possibility of the use of toxic sugar baits for the control of these vectors. The knowledge of feeding behavior in these insects can be fundamental for the development of new strategies to control Chagas disease.

Adult dietary experience influences mortality of the pest melon fly, Zeugodacus cucurbitae (Diptera: Tephritidae), to an ingested toxin

AbstractIngested toxins formulated as baits can be effective in the management of insect pests, but their efficacy may be influenced by insect foraging alongside active ingredients. There are several components that might influence insect consumption of toxic baits, one of which being prior nutritional exposure. In our study, we investigated how protein deprivation following adult emergence influences lethal and sublethal effects of boric acid on the pest tephritid melon fly, Zeugodacus cucurbitae. We performed a series of experiments to address the impact of prior diet on mortality, diet consumption, enzymes involved in detoxification and antioxidation and fly activity. Newly emerged melon fly adults were provided either diet containing 3:1 sucrose/yeast hyrdrolysate or just sucrose for three days prior to bioassays. Overall, protein deprivation had a strong effect on fly interactions with boric acid. In two separate experiments (continuous exposure and short duration feeding), insects only pre‐fed sucrose had significantly higher mortality compared with those pre‐fed protein. Insects that were pre‐fed only sucrose removed more liquid diet over the same duration of the experiments, suggesting compensatory foraging behaviours. Adults pre‐fed sucrose had higher catalase (1.5×) and superoxide dismutase (1.7×) activities compared with adults pre‐fed sucrose‐yeast, but we found no effect of boric acid on their activity or that of glutathione‐S‐transferase or acetylcholinesterase activity. Boric acid consumption also significantly reduced the activity of melon flies. Overall, our results demonstrate that prior diet in fly adulthood can impact subsequent exposure to and efficacy of ingested toxicants.

Therapeutic Importance of Extracts from Leaf and Bark of <i>Gymnacranthera farquhariana</i>

Background: Gymnacranthera farquhariana (Hook. f. and Thomson) Warb. is one of the endangered tree taxon of the Western Ghats, a biodiversity hot-spot in peninsular India. Very few reports are available on biological applications of the bark, leaf and seed of this plant. Aim: The present work deals with the screening of methanol and aqueous extracts of G. farquhariana from leaf and bark for therapeutic importance. Methods: Anti-bacterial activities of extracts were carried out using two bacterial strains viz., Pseudomonas aeruginosa and Staphylococcus aureus through the agar well diffusion method. The antifungal activities by poison bait method using Aspergillus niger, Colletotrichum gloeosporioides and Fusarium solani. Each experimental parameter was conducted in triplicate. Results: The results showed that G. farquhariana bark and leaf extracts exhibited promising activities against bacteria. Antifungal activity also showed good inhibition activity. The extracts showed a good anti-diabetic potential in α-amylase inhibitory assay. Bark aqueous extract showed 54.79% inhibition for α- amylase inhibition assay at 250μL. The extract also showed good anti-inflammatory potential in the Bovine Serum Albumin (BSA) denaturation assay. Bark aqueous extract showed 83.9% inhibition for BSA denaturation assay at 100 μL. Conclusion: Both leaf and bark extracts of the plant showed good antioxidant, anti-diabetic and antimicrobial activity. This is the first such in vitro report concerning G. farquhariana plant parts.

Comparing efficiencies of population control methods for responding to introductions of transboundary animal diseases in wild pigs

Introductions of transboundary animal diseases (TADs) into free-ranging wildlife can be difficult to control and devastating for domestic livestock trade. Combating a new TAD introduction in wildlife with an emergency response requires quickly limiting spread of the disease by intensely removing wild animals within a contiguous area. In the case of African swine fever virus (ASFv) in wild pigs (Sus scrofa), which has been spreading in many regions of the world, there is little information on the time- and cost-efficiency of methods for intensively and consistently culling wild pigs and recovering carcasses in an emergency response scenario. We compared the efficiencies of aerial operations, trapping, experimental toxic baiting, and ground shooting in northcentral Texas, USA during two months in 2023. Culling and recovering carcasses of wild pigs averaged a rate of 0.15 wild pigs/person hour and cost an average of $233.04/wild pig ($USD 2023) across all four methods. Aerial operations required the greatest initial investment but subsequently was the most time- and cost-efficient, costing an average of $7266 to reduce the population by a standard measure of 10 %, including recovering carcasses. Aerial operations required a ground crew of ∼7 people/helicopter to recover carcasses. Costs for reducing the population of wild pigs using trapping were similar, although took 13.5 times longer to accomplish. In cases where carcass recovery and disposal are needed (e.g., response to ASFv), a benefit of trapping was immediate carcass recovery. Toxic baiting was less efficient because both culling and carcass recovery required substantial time. We culled very few wild pigs with ground shooting in this landscape. Our results provide insight on the efficiencies of each removal method. Strategically combining removal methods may increase overall efficiency. Overall, our findings inform the preparation of resources, personnel needs, and deployment readiness for TAD responses involving wild pigs.

Mycotoxicity of leaf extract of Tabernaemontana pachysiphon Stapf against Fusarium oxysporum Schlecht, a postharvest fungal rot pathogen of taro

Taro, otherwise known as cocoyam, is one of the major sources of calories in the tropics. However, losses of its corm during storage are high, partly due to pathogenic diseases. Fusarium oxysporum is one of the principal fungal pathogens causing about 50% of postharvest losses of taro corms in the tropics. The rise in pesticide-resistant fungal pathogens, amongst other factors, has necessitated the recent search for alternatives to synthetic pesticides. This work aimed to evaluate the effects of six concentrations (0%, 10%, 20%, 30%, 40%, and 50%) of aqueous leaf extract of T. pachysiphon on spore germination, mycelial growth and reproduction of F. oxysporum both in vitro and in vivo. The in vitro experiment was conducted using the poison bait technique, while the in vivo experiment involved 21 corms (200 g) artificially infected with F. oxysporum and treated with the respective concentrations of the test extracts or griseofulvin. The control consisted of fungus-infected corms only. Generally, the experiments consisted of 7 treatments replicated 3 times and were laid out in a completely randomized design. Results of the cultures studies showed that all aqueous extract of T. pachysiphon significantly (P< 0.05) and to varying degrees impeded spore germination (56.38–70.24%) and retarded radial growth of the pathogen (68.27–82.01%). The percentage rot expression in the living tissues treated with the extracts ranged between 19.4% and 40.4%. All results were statistically (P< 0.05) superior to the control but comparable to the results (75.06%, 86.41%, and 17.2%) obtained with griseofulvin for these features, respectively. The inhibitions were linearly correlated with the dose of application of the biotoxicant both in vitro and in vivo.

Synergistic Antifungal Activity of Green Synthesized Zinc Oxide Nanoparticles and Fungicide Against Rhizoctonia solani Causing Rice Sheath Blight Disease.

The biosynthesis of metal oxide nanoparticles using leaf extract of medicinal plants is a promising substitute for the traditional chemical method. This work aimed to synthesize zinc oxide nanoparticles using a green approach from local "Dholkolmi" (Ipomoea carnea) leaf extract which is a medicinal plant growing outside the roads of different regions of Bangladesh. The biosynthesized zinc oxide nanoparticles (ZnONPs) were characterized using ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, particle size analyzer, zeta-potential, scanning electron microscopy-energy dispersive spectroscopy, field emission scanning electron microscopy, and transmission electron microscopy. The results of UV-visible spectrophotometers observed an absorption peak at 373 nm wavelength, which confirmed the synthesis of ZnONPs in the solution. ZnONP sizes determined by XRD, DLS, and TEM are approximately ~37 nm, 105.61 nm, and 19.66 nm, respectively. ZnONPs were present because of the strong oxygen and zinc signals in the EDX profile. Additionally, this research assessed the antifungal activity of the biosynthesized ZnONPs and as well as folicur-incorporated ZnONPs against Rhizoctonia solani by the poison bait technique. According to the result of this study, ZnONPs synthesized from Ipomoea carnea leaf extract showed no promising result against Rhizoctonia solani mycelial growth reduction. But folicur-incorporated ZnONPs revealed a significant finding with a maximum 100% inhibition of mycelial growth at 1:1 and 3:1 ratio of ZnONPs with folicur fungicide under in vitro conditions. In the net house experiment, folicur-incorporated ZnONPs at a 1:1 ratio of ZnONPs with folicur showed considerable disease inhibition (26.96% RLH) as compared to disease control (52.83% RLH). In the case of rainfed transplanted Aus (March-June), the highest percentage of RLH was recorded in disease control (64.61%), and the lowest RLH was found in folicur (24.79%) followed by a 1:1 ratio of ZnONPs with folicur (32.10%) in field condition. On the other hand, the highest percentage of RLH was recorded in disease control (65.31%) and the lowest RLH was found in folicur (18.14%) followed by a 1:1 ratio of ZnONPs with folicur (21.39%) in rainfed transplanted Aman (July-November) season. The findings of the in vitro and in vivo studies provided evidence that ZnONPs and folicur had a strong synergistic antifungal impact and may be employed as a possible rice sheath blight disease management agent.

The Determination of the Prohibited Herbicide 4,6-Dinitro-Ortho-Cresol (DNOC) in Poisoned Domestic and Wild Animals in Italy.

This study reports the determination of DNOC in the baits and gastric contents of poisoned dogs and wild canids collected in the Abruzzo region between 2014 and 2022. A total of 663 samples of the baits and carcasses of domestic and wild animals were analyzed for the determination of DNOC through GC-MS. DNOC was found to be present in 58 cases from 663 analyzed samples, with 49 poison baits and nine gastric content samples from dogs and red foxes. This study confirms for the first time that the banned pesticide DNOC still poisons both domestic and wild animals in the Abruzzo region. It should be considered that this study was carried out on a population of animals from a regional geographical area, and more detailed country-wide studies need to be carried out to obtain the incidence of poisoning from this herbicide in Italy. Furthermore, these findings emphasize the importance of considering this chemical in differential diagnosis during toxicological investigations of animal poisoning.

Feral cat control: improving Eradicat® bait efficiency and effectiveness for fauna conservation in the Southern Jarrah Forest, Western Australia

Context Toxic meat baits are the most effective broadscale method used for reducing the densities and impacts of feral cats (Felis catus) on vulnerable Australian native fauna when alternative prey is minimal. Aims Our aim was to assess the efficiency (proportion of baits removed by target animals) and effectiveness (proportion of target animals removed) of Eradicat® baits and to identify how their use may be improved in Southern Jarrah Forest ecosystems of Western Australia. We sought to determine how, when, and where best to deploy baits using the current Eradicat® bait prescriptions to maximise the reduction of feral cats. Methods Eradicat® uptake trials were conducted over a 15-month period using remote sensor cameras (RSCs) to observe animals interacting with the baits at 40 sites. Ten successive baiting trials were conducted, each involving four randomly selected sites (two replicates for each of two bait deployment methods: clusters and transects). Key results The fate of 5658 Eradicat® baits at 2000 bait locations was recorded during 54,361 camera trap nights. Despite occupancy rates being high for cat and fox (Vulpes vulpes), (92% and 84%, respectively), the efficiency and effectiveness of Eradicat® baits was low for both introduced predators (cat: 0.1% and 10–12%, respectively; and fox: <0.6% and 8–20%, respectively). There were no major differences in baiting efficiency in relation to bait deployment method or time of year. More than half (56–58%) of the baits were removed by non-target animals prior to an introduced predator being observed on camera at the bait location. Along transects, there were more cat and fox visits closer to tracks and surface water features. Foxes were also more likely to visit bait locations closer to private property. Younger cats appeared to be more interested and more likely to eat a bait than older cats. Conclusions Substantial improvements could be made by increasing bait availability (reducing non-target interference), detectability and attractiveness to cats. Implications Additional introduced predator threat abatement methods may be needed for the conservation and recovery of many threatened native mammals in the Southern Jarrah Forests and elsewhere in Australia. Feral cat baiting should be conducted within an integrated and holistic invasive animal management system.

Novel acrylamide-based baits for effective control of subterranean termites (Blattodea: Rhinotermitidae).

Acrylamide-based bait has super water absorption making it highly attractive to subterranean termites that are lured by wood with high water content. This study investigated the control efficiency of these baits on subterranean termites. In particular, we evaluated the water-absorption capacity, attractiveness to subterranean termites, and control efficiency of these baits on subterranean termites through wooden blocks (Populus deltoides and three types of particleboards). The results indicated a substantial water absorption capacity of acrylamide (70.6%; control: 14.8%) and a strong attraction for feeding subterranean termites (P. deltoides: 198 highest; 81 lowest subterranean termites individuals; combination of neem leaves and walnut shells: 168 highest; 36 lowest subterranean termites individuals). When acrylamide was combined with boric acid at the highest concentration, it resulted in the lowest wood consumption rates (P. deltoides: 24.1%; control: 63.8%, combination of neem leaves and walnut shells: 32.5%; control: 62.1%). In conclusion, this research supports the commercial viability of employing innovative acrylamide-based toxic baits and particleboards for subterranean termite management. © 2024 Society of Chemical Industry.

A descriptive study of poisoners and users of other indiscriminate means to illegally control wildlife in Spain

AbstractPoison and other indiscriminate means are used illegally for wildlife control worldwide. This pervasive phenomenon can significantly damage ecosystems overall and be particularly harmful to certain species (endangered or otherwise) that are susceptible to poisoned baits. Poisoning (and co‐occurring poaching) jeopardizes public administration efforts to reintroduce or support the populations of certain species, while the favored toxic substances used pose a major threat not only to the biodiversity of habitats but also to human health. Both alleged and actual harm to crops and hunting resources are the main driver of illegal vermin and predator control. Previous studies on poisons and other nonselective methods of wildlife elimination have focused on the means used and the species affected. We have instead taken a global empirical approach, also analyzing contextual aspects, what motivates perpetrators and, eventually, the characteristics of the poisoners and users of various indiscriminate means for illegal wildlife control in Spain. This analysis is derived from a thorough examination of incidents based on the investigation of perpetrator by police and judicial records. Furthermore, this work provides a methodological framework that serves as first approach to this issue, gaining insight into the formulation of preventive policies and improving decision taking by law enforcement agencies.

Low secondary risks for turkey vultures from a sodium nitrite toxic bait for wild pigs

AbstractAn acute and orally‐delivered toxic bait for wild pigs (Sus scrofa) containing sodium nitrite (SN) is being developed and tested for potential registration in the U.S. We evaluated oral toxicity of SN and risk of secondary consumption in a common avian scavenger, the turkey vulture (Carthartes aura), by 1) conducting an acute oral toxicity test (LD50) for turkey vultures by oral gavage, and 2) allowing turkey vultures to feed on whole carcasses and digestive tracts of wild pigs that died from consuming SN‐laden bait. Captive tests were conducted during fall 2016 and spring 2017 in the Wild Pig Research Facility at Kerr Wildlife Management Area, Hunt, Texas, USA. We estimated the LD50 of SN for turkey vultures at 659 mg/kg. None of the turkey vultures died or exhibited any symptoms of SN‐toxicity from consuming whole carcasses, or digestive tracts of wild pigs that were poisoned with SN. We concluded that the risks of secondary poisoning to turkey vultures are low, which agrees with previous work on another scavenger, the coyote (Canis latrans). Overall, we found no evidence to suggest that 2 common scavengers would be at risk of acute mortality from consuming wild pigs that were poisoned with SN.

Nasturtium leaf compounds, diphenyl disulfide and lyral, against Atta sexdens (Hymenoptera: Formicidae) and their symbiotic fungi.

Social insect pests, particularly leaf-cutting ants, present a considerable challenge in terms of control. Leaf-cutting ants are significant agricultural, forestry, and pasture pests, and understanding their behavior and defense mechanisms is essential for managing their colonies effectively. While toxic ant baits are a primary control method, the limited availability of effective insecticides and concerns over their hazardous nature has spurred the search for alternative solutions, particularly natural compounds, which aligns with the goals of forest certification groups. In the light of previous evidence demonstrating the efficacy of nasturtium leaves (Tropaeolum majus L. (Brassicales: Tropaeolaceae)) in suppressing leaf-cutting ant colonies, this study investigates 2 active components of nasturtium leaf extracts: diphenyl disulfide and lyral. We tested their impact on Atta sexdens (L.) (Hymenoptera: Formicidae), the most prevalent leaf-cutter ant species in Brazil, and their symbiotic fungus, Leucoagaricus gongylophorus (Möller) Singer (Agaricales: Agaricaceae). We conducted experiments with increasing concentrations of diphenyl disulfide and lyral, assessing their effects on the symbiotic fungus and on forager workers and gardeners of A. sexdens colonies. Our findings revealed no fungicidal activity, and ant mortality was minimal in both topical and ingestion bioassays with the exception of gardeners topically exposed to diphenyl sulfide. Furthermore, the compounds did not affect leaf ingestion, but diphenyl disulfide did increase interactions among foragers. These results suggest that neither diphenyl disulfide nor lyral are the primary contributors to the suppression of leaf-cutting ant colonies by nasturtium leaves. However, they may enhance the formicidal activity of other compounds present in nasturtium leaves.

Boric acid toxic sugar bait suppresses male Aedes aegypti (Diptera: Culicidae): wing beat frequency and amplitude, flight activity, fecundity, insemination, and mate-finding Allee effect.

Controlling the spread of arboviral diseases remains a considerable challenge due to the rapid development of insecticide resistance in Aedes mosquitoes. This study evaluated the effects of boric acid-containing toxic sugar bait (TSB) on field populations of resistant Aedes aegypti mosquitoes. In addition, this study examined the flight activity and wing beat frequency and amplitude of males and the flight activity, fecundity, and insemination of females after pairing with males exposed to TSB. The population dynamics of Aedes mosquitoes under imbalanced sex ratios were examined to simulate realistic field conditions for male suppression under the effect of TSB. The mortality of male mosquitoes was consistently high within 24 h after exposure. By contrast, the mortality of female mosquitoes was inconsistent, with over 70% mortality observed at 168 h. The flight activity and wing beat amplitude of treated males were significantly lower than those of controls, but no significant difference in wing beat frequency was detected. The fecundity and insemination of treated female mosquitoes were lower than those of controls. A simulation study indicated that considerably low male population densities led to mating failures, triggering a mate-finding Allee effect and resulting in persistently low population levels. Boric acid-containing TSB could effectively complement current chemical intervention approaches to control resistant mosquito populations. TSB is effective in reducing field male populations and impairing male flight activity and female-seeking behavior, resulting in decreased fecundity and insemination. Male suppression due to TSB potentially results in a small mosquito population. © 2024 Society of Chemical Industry.

Widespread use of anticoagulant rodenticides in agricultural and urban environments. A menace to the viability of the endangered Bonelli's eagle (Aquila fasciata) populations

Anticoagulant rodenticides (ARs) are one of the most toxic groups of compounds currently used worldwide for rodent pest control. Toxic baits are often, directly or indirectly, ingested by non-target animals, resulting in secondary poisoning and frequently affecting apex predators. Their presence in many species of raptors is quite common, particularly scavenger species, with some of these acting as sentinels for the presence of these substances in the environment. However, there is less data on the presence of ARs in Bonelli's eagle, one of the most endangered eagle species in Spain and which is experiencing a negative population trend in Europe. This medium-sized eagle feeds predominantly on live species, and rarely consumes carrion.In this study, 17 carcasses of Bonelli's eagles from the Eastern Spain were necropsied. Both first and second generation ARs in their livers were analyzed by HPLC-MS-TOF revealing that all the eagles studied had been exposed to at least 5 ARs, out of a total of 10 ARs analyzed, with 7 being the highest number of ARs detected in a sample. Second generation ARs were the most prevalent, particularly bromadiolone and brodifacoum, with the highest concentrations in 94% of the cases. More than a third of the eagles presented a liver concentration of greater than 200 ng/g ARs, suggesting AR poisoning.The elevated presence of these compounds in Bonelli's eagles could be a new cause of mortality for this species or could explain other causes of death, such as the increased mortality in power lines, and should be taken into account for their conservation. At the same time, the presence of these compounds in the environment also represents a risk to public health, as the most frequent species in the diet of Bonelli's eagle (rabbits and partridges) are also hunted and consumed by hunters and their families.

Repellent potential of agroecological extracts: Exploring their efficacy against the leaf‐cutting ant Acromyrmex subterraneus in the laboratory

AbstractThe increasing restrictions on commercial toxic baits for controlling leaf‐cutting ants have started a “gold rush” for alternative compounds, with agroecological extracts emerging as a promising option. Here, we tested for the first time the repellent effects of concentrated and diluted ant extracts and cow urine solution on laboratory colonies of Acromyrmex subterraneus (Forel) (Hymenoptera: Formicidae). The agroecological extracts preparation and application followed the information provided by peasants from the Movimento dos Trabalhadores Rurais Sem Terra in Brazil who carry out agroecology. First, we applied the agroecological extracts in the middle segment of the upper path of a foraging trail to determine whether they act as a chemical barrier. All agroecological extracts induced the deviation of the foraging flow from the upper path to the lateral path. However, only the concentrated ant extract reduced the leaf delivery rate. Also, we applied the agroecological extracts directly on the leaf disks and conducted a paired selection test. The proportion of transported leaf disks with concentrated ant extract and cow urine solution was lower than that of control disks. We suggest that the observed repellent efficacy of the concentrated ant extract may stem from its content of chemical compounds belonging to the same chemical group as the alarm pheromones found by other Acromyrmex species. As for the cow urine solution, we attribute its repellent effect to the presence of urea. Our findings highlight a significant repellent potential of the concentrated ant extract and cow urine solution for leaf‐cutting ants, which may be applied both on foraging trails and on leaves of cultivated plants.

Polyols induce acute oxidative stress and mortality in Indian malaria vector Anopheles stephensi (Diptera: Culicidae): potential for use as sugar-cum-toxin source in toxic sugar baits.

Development of insecticide resistance in the major malaria vectors has necessitated the development of novel vector control tools. One such strategy involves the use of toxic sugar baits that targets the sugar-feeding behaviour of mosquito vectors. In this study, we investigated the potential of polyols, as a toxic food (sugar) source in toxic sugar baits against the malaria vector Anopheles stephensi Liston. We examined the acute toxicity of six polyols, namely, erythritol, glycerol, mannitol, propylene glycol (PG), sorbitol, and xylitol on adult female An. stephensi mosquitoes at two different concentrations - 2% and 10%. We also studied changes in fecundity, egg hatchability and mid-gut peroxide levels induced by polyol exposure. Among the six polyol compounds tested, PG was most toxic and lethal followed by glycerol and erythritol (P < 0.001) compared to the control (sucrose). PG induced acute mortality at different tested concentrations. In the erythritol- and glycerol-fed groups, a dose-dependent effect on mortality was observed. Glycerol evidently reduced fecundity and egg-hatchability in gonotrophic cycles G1 and G2. Sucrose was the preferred food source (48%), followed by erythritol (18%), PG (10%) and glycerol (8%). Ingestion of polyols increased peroxide levels in mosquito guts, which persisted for extended durations ultimately resulting in rapid mortality (P < 0.05). The present study highlights the usefulness of sugar polyols for the development of toxic sugar baits with minimal yet effective ingredients. Further research could be focused on field experiments and on the exploration of synergistic effects of different polyols for optimization of field applications. © 2024 Society of Chemical Industry.