Toxic Baits Research Articles

Mechanical and Chemical Management of Wild Boar (Sus scrofa L.) Pests in the Bireuen District of Aceh Province

The agricultural sector, including food crops, plantations, fisheries, livestock, and forestry, plays an essential role in the development of the national economy development. The infestation of pests, diseases, and weeds is one of the constraints to obtaining optimal crop production. One of the major pest, especially on estate crops, is wild boar (Sus scrofa L.). The damage caused to plantation commodities, especially those bordering the forest, is very significant. Therefore, it needs to be controlled. The objectives of this research were to study: Food bait preference, mechanical control using hook bait and snare trap, and chemical control using zinc phosphide as acute poison. This research was designed using block randomized experimental design to treat of baits (banana fruit, jackfruit, and cassava) and treatment villages (Puuek and Jambo Dalam in Peulimbang District; Blang Beururu and Ara Bungong in Peudada District). Data were analyzed using Minitab v. 16 for windows 8, then analyzed using the Tukey test at a level of α=5%. Consumption of wild boar in Blang Beururu Village was the lowest and significantly different from the other three villages. Bait preference trial showed that wild boar consumed more cassava in Peulimbang and more jackfruit in Peudada. Jackfruit, cassava, and banana baits were consumed in the same amount. Therefore, we used cassava for the subsequent trial. Wild boar consumed poison bait and hooked bait in Peudada higher than in Peulimbang. Poison bait, hook bait, and control were consumed simultaneously at the same amount. Wild boar was caught by snare trap more in Peulimbang than in Peudada.

A synthetic lure for Anopheles gambiae (Diptera: Culicidae) based on the attractive plant Parthenium hysterophorus.

Sugar is the sole diet for male mosquitoes and a complementary meal for females. Searching for natural sources of sugar is mediated by semiochemicals. Floral nectars, extra floral nectaries, damaged tissues of plants and rotten fruits are the most common sources of sugar in nature. I provide laboratory evidence of the high attraction of Parthenium hysterophorus L., a weed that grows in tropical climates, to Anopheles gambiae Giles. This study has tried to identify the chemicals which might be involved in the chemical attraction of A. gambiae to this plant. Using quantitative GC-MS analysis, α-pinene, camphene, 1-octen-3-ol, β-pinene, cis-β-ocimene, bornyl acetate, α-caryophyllene, hexadecanoic acid, and α-linolenic acid were identified as the main constituents of P. hysterophorus volatiles. Successive olfactory assays helped a better understanding of the more attractive chemicals of P. hysterophorus to A. gambiae which was the basis for testing a possible synthetic blend. Olfactory experiments proved this synthetic blend to be as attractive as Parthenium intact plants for A. gambiae. A minimal blend, consisting of only α-pinene, camphene, and cis-β-ocimene, was also produced and laboratory experiments indicated its relative attraction for A. gambiae. This blend can be tested in the attractive toxic sugar bait stations for sampling, surveillance, or control programs of mosquitoes in tropical Africa, where A. gambiae sensu stricto transfer malaria among residents.

Diols and sugar substitutes in attractive toxic sugar baits targeting Aedes aegypti and Aedes albopictus (Diptera: Culicidae) mosquitoes.

Around the world, mosquitoes continue to transmit disease-causing pathogens and develop resistance to insecticides. We previously discovered that a generally regarded as safe (GRAS) compound, 1,2-propanediol, reduces adult mosquito survivorship when ingested. In this study, we assess and compare 5 more chemically related compounds for mosquito lethality and 8 GRAS sugar substitutes to determine toxicity. We conducted a series of feeding assays to determine if ingesting the compounds influenced mosquito mean survivorship in locally collected lab-reared populations of Aedes aegypti (Diptera, Culicidae, Linnaeus, 1762) and Aedes albopictus (Diptera, Culicidae, Skuse, 1894) mosquitoes. Our results indicate that 1,2-propanediol, 1,3-propanediol, 1,5-pentanediol, 1,6-hexanediol, 2-methyl-1,3-propanediol, DL-dithiothreitol, acesulfame potassium, allulose, erythritol, sodium saccharin, stevia, and sucralose significantly reduced the mean survivorship of one or both species. Short-term trials with the most toxic compounds revealed that they could substantially affect survivorship after 24 h. We also found that there were different responses in the 2 species and that in several experimental conditions, male mosquitoes expired to a greater extent than female mosquitoes. These findings indicate that several of the compounds are toxic to mosquitoes. Further study is required to determine their effectiveness in attractive toxic sugar baits (ATSBs) as a potential component of population control strategies.

Mitigating neophobia behaviour of Bandicota bengalensis in accepting poison bait and traps using sulphur compounds as additives

This study aimed to assess the potential of five different sulphur compounds, namely carbon disulphide, dimethyl sulphoxide, dimethyl sulphide, allyl sulphide, and dimethyl disulphide as bait additives in mitigating neophobia behaviour of Bandicota bengalensis towards poison bait and traps. The efficacy of different concentrations (5, 10, 20, 50, and 100 ppm) of each of the sulphur compounds in enhancing bait acceptance was evaluated by exposing them to rats in a laboratory setting. The results showed significantly higher acceptance of bait containing 5 ppm concentration of all the compounds. Moreover, exposure of bait mixed with 5 ppm of all the compounds under multi-choice condition in radial maze revealed higher consumption by female rats of bait admixed with carbon disulphide, while male rats consumed the baits containing carbon disulphide and dimethyl sulphide to a greater extent. Female rats showed significantly higher acceptance (76.22%) of 2% zinc phosphide bait admixed with 5 ppm of carbon disulphide while male rats showed significantly higher acceptance of 2% zinc phosphide bait admixed with carbon disulphide (70.83%) and dimethyl sulphide (60.28%). Field experiments showed that 2% zinc phosphide bait mixed with 50 ppm carbon disulphide significantly reduced rodent activity in wheat crop fields. In laboratory and semi-field conditions, carbon disulphide at a concentration of 5 ppm and, in crop fields, at a concentration of 50 ppm, increased the efficacy of multi-catch traps for B. bengalensis. The study suggests that using carbon disulphide can enhance poison bait acceptance and trapping, thereby mitigating neophobia behaviour and improving rodent control success.

LABORATORY EXPLORATION OF TOLFENPYRAD AND NATURECIDE IN TOXIC SUGAR BAITS AGAINST AEDES AEGYPTI

Attractive toxic sugar baits (ATSB) are an effective mosquito control tool based on sugar feeding behaviors and oral ingestion. There is a demand from consumers for more effective active ingredients. Torac 15EC, containing tolfenpyrad, is a registered insecticide for control of agricultural pests, which may mean transferability to mosquito control. Another option, Naturecide Pest Management (NPM), is a botanical insecticide containing cedarwood and cinnamon oils for control of adult mosquitoes via contact. This study evaluated tolfenpyrad and a formulated essential oil blend added to toxic sugar baits (TSB) against adult Aedes aegypti, compared with a positive control of 1% boric acid toxic sugar bait, and untreated control. In this experiment setup, ingestions of tolfenpyrad at 1%, NPM at 1% (of finished product) TSB, and boric acid at 1% by female Ae. aegypti mosquitoes resulted in average mortality at 48 hrs were 71%, 73% and 95%, respectively. The results suggest that ingestible tolfenpyrad, Naturecide Pest Management, and boric acid TSBs may be potential tool for mosquito control strategies and programs, but the mode of action of essential oils to kill adult mosquitoes is still needed to be addressed.

ADULTICIDAL AND LARVICIDAL IMPACTS OF THE MIXTURE OF BACILLUS THURINGIENSIS ISRAELENSIS AND BORIC ACID TOXIC SUGAR BAIT (TSB) AGAINST AEDES AEGYPTI AND CULEX QUINQUEFASCIATUS

Toxic sugar baits (TSBs) can be used to deliver insecticide material via ingestion instead of via contact through spraying of insecticides by targeting the resting and sugar-feeding behaviors of adult mosquitoes. This semi-field study aimed to evaluate the adulticidal and larvicidal dual action of a foliage spray of a TSB with a mixture of Bacillus thuringiensis israelensis (Bti), and boric acid against Aedes aegypti Puerto Rico (PR) strain (resistant) and Orlando (OR) strain (susceptible), and laboratory colony of Culex quinquefasciatus (Gainesville 1995 strain). The larval and adult evaluation of TSB consisted of 11% VectoBac (Valent Biosciences, Libertyville, IL; Bti), 5% boric acid, and 10% sucrose solution. The TSB intervention for adults consisted of the same as the larval intervention but had an addition of a food grade, 5g Blue No. 1 dye (Sigma Aldrich; St. Louis MO) to observe adult feeding. The controls received a 10% sucrose solution. For the larval mortality evaluation, the TSB was applied to the bromeliad with the runoff dripping into pans containing mosquito larvae. At 24 hours post-application, 100% larval mortality was observed. At all-time mortality recordings, 50 larvae were introduced into the larval pans and the bromeliads were sprayed with water to mimic rainfall allowing the remaining TSB to be washed off into the larval pans. After the 4th day of larval introductions, larval mortality was 83.5% ± 14.3 for Ae. aegypti_PR, 92.5% ± 6.1 for Ae. aegypti OR, and 97 % ±1.7 for Cx. quinquefasciatus. Total mean mortality at 72 hours post exposure for the adult TSB evaluation was 52.7% ± 24.2 for Ae. aegypti_PR, 34.3% ± 26.5 for Ae. aegypti_OR, and 73.7% ± 13.9 for Cx. quinquefasciatus. Our study suggests this TSB including Bti is effective against larvae when applied as an adulticide barrier application and could be a dual-action approach to mosquito control.

Enhancing toxic sugar meals against Aedes aegypti (Diptera: Culicidae) by adulterating with erythritol in combination with other active ingredients.

Attractive toxic sugar baits (ATSBs) are an underexploited method for mosquito control. For ATSBs to be more widely accepted, demonstrably effective ingredients need to be verified. We investigated erythritol as a toxic additive in sugar meals against Aedes aegypti (L.) for potential future use in ATSBs. Erythritol is a sugar alcohol that is commonly used as a sugar substitute, while also being toxic to mosquitoes. Our studies tested formulations of erythritol, sucrose, and blends of both. Secondary investigations included combinations with the active ingredients Bacillus thuringiensis israelensis, spinosyn, and boric acid. Adult Ae. aegypti were separated into test groups and provided various combinations. Formulations containing erythritol, with or without another toxicant, exhibited 90% mortality within 72 h of observation (P = 0.03192). Additionally, erythritol appeared more effective when combined with sucrose in a 1:1 ratio (5% concentration each). This combination showed a 24% and 85% increase in mortality when combined with boric acid and Bti, respectively, at 48 h compared with equivalent groups containing only 10% sucrose. Erythritol appears to kill adult mosquitoes, even in relatively low concentrations, without another toxicant being required. However, erythritol also effectively enhances kill of main ingredient toxicants such as boric acid and Bti, showing a supporting role. The low concentration of erythritol needed to provide significant kill, its ability to fill in as both a sugar base and toxicant, and its ability to be safely handled by humans makes erythritol a strong candidate for use as a supporting ingredient in future bait formulations.

Biochemical, Histological Changes, Protein Electrophoretic Pattern, and Field Application of CuPb-Ferrite/TiO2 Nanocomposites for Controlling Terrestrial Gastropod Eobania vermiculata (Müller).

Eobania vermiculata is a hazardous snail that can damage ornamental plants and cause significant harm to plant sections in Egyptian areas. Herein, the molluscicidal activity of CuPb-Ferrite/TiO2 and TiO2 nanoparticles (NPs) against E. vermiculata was evaluated using the poisonous bait method. LC50 values were determined using the leaf dipping and contact methods, with values of 631.23 and 1703.49 ppm for CuPb-Ferrite/TiO2 and 193.67 and 574.97 ppm for TiO2. Exposure to both NPs resulted in a significant increase in the biochemical parameters of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP), as well as a decrease in total protein (TP) percentage of E. vermiculata. Histological examinations revealed that many digestive cells had ruptured, and their contents had been lost, while the foot's epithelial layer became ruptured. The average reduction was 66.36% for CuPb-Ferrite/TiO2 NPs compared to the recommended molluscicide, Neomyl, with a 70.23% reduction in the field application. Electrophoretic separation of total protein using sodium dodecyl sulfate-polyacrylamide gel electrophoresis after treatment with LC50 concentrations of TiO2 and CuPb-Ferrite/TiO2 demonstrated the potency of these synthetic compounds as molluscicidal agents. Therefore, we recommend the use of CuPb-Ferrite/TiO2 NPs as a novel land snail molluscicide because it is safe to use, and the baits are arranged to not affect irrigation water, with a high molluscicidal effect.

Contamination and mortality of leaf-cutting ant workers by the quinone inside inhibitor fungicide after social interactions

Leaf-cutting ants of the genera Atta and Acromyrmex (Hymenoptera: Formicidae) are the most important pests in forest and agricultural plantations and livestock. Toxic baits are the main method to manage these insects. The objective was to determine whether the behavior of allogrooming, touch, and self-grooming among Atta sexdens rubropilosa Forel, 1908 (Hymenoptera: Formicidae) workers disperse the fungicide quinone inside inhibitor and whether this product is toxic to them. This fungicide was applied, topically, in groups of workers and the social interactions between them and their mortality with and without the fungicide were evaluated. The interactions and the quinone inside inhibitor fungicide contamination increased with the number of leaf-cutting ant workers per group. Excessive touches, with subsequent allogrooming, and self-grooming among the ant workers dispersed the quinone inside the inhibitor fungicide causing 100% mortality and indicating its toxicity to this insect. The hypothesis that social interactions contaminated ant colony mates and the toxicity of the fungicide quinone inside inhibitor to workers of the leaf-cutting ant A. sexdens rubropilosa was proven.

Mesopredator release among invasive predators: Controlling red foxes can increase feral cat density and alter their behaviour

Abstract1. The mesopredator release theory predicts that the density of subordinate predators will increase as dominant predators decline. Persistent debate around mesopredator release in part reflects the lack of robust, replicated experiments that test this theory, and the use of population indices that confound changes in mesopredator density and detectability. This uncertainty has immediate impacts for conservationists who are faced with managing sympatric invasive predators.2. We used replicated experimental designs and spatially explicit models to examine whether mesopredator release of the feral cat Felis catus occurs in response to targeted control of the introduced red fox Vulpes vulpes. We surveyed three Control‐Impact paired landscapes in a region with long‐term fox control (1080 poison baiting) and conducted a Before‐After Control‐Impact Paired‐Series experiment in another region. We used fox occurrence as a simple metric of fox populations and estimated feral cat density with spatial mark–resight models.3. Lethal fox control had varying effects on fox occurrence, consistent with variation in the duration and intensity of poison baiting. Correspondingly, responses in feral cat density ranged from negligible to a 3.7‐fold higher density in fox‐baited landscapes. At a fine spatial scale (200 m2), feral cat density was negatively associated with fox occurrence probability across both regions. These results were consistent with mesopredator release, although uncertainty was high in the region where fox control had only recently commenced.4. Feral cat detectability also varied across the (artificially manipulated) gradients of fox occurrence probability. In one region, nonlinear models indicated that feral cats had lower detection and increased movement rates when foxes were uncommon, giving way to density suppression at high fox occurrence probabilities.5. Synthesis and applications. Our study provides replicated, experimental evidence that dominant predator suppression can be associated with a higher mesopredator density. Mesopredator release can manifest as changes in both behaviour and density, distorting inference if these processes are not distinguished. Our results may help explain why fox control does not consistently improve native prey persistence, suggesting integrated pest management may be necessary to improve conservation outcomes.

Retrospective analysis of forensic toxicology data from 2021 to identify patterns of various forensic cases

PurposeKnowing and analyzing the characteristics and trends of forensic toxicology cases in a certain area is particularly important for a local government to establish an effective prevention and control system. The purpose of this work was to summarize data from forensic toxicology cases received by the Academy of Forensic Sciences (AFS) in 2021. MethodsAs requested by the police or according to the details of cases, samples were systematically screened or analyzed by various methods. Liquid chromatography-tandem mass spectrometry and gas chromatography-mass spectrometry were used to identify medicinal drugs, drugs of abuse, pesticides, poison gases, etc. ResultsAFS received a total of 17,758 cases in 2021, of which 314 cases underwent autopsy. The main cause of death was sudden death, and the manner of death was mainly accident. Among 13,744 drug abuse cases, the number of positive cases was 1721, with a positive rate of 12.5%, and synthetic cannabinoids were the most frequently detected substances. In 3640 traffic cases, 85.3% of drivers were suspected of drunk driving. In 103 poisoning cases, hydrogen sulfide poisoning and pesticide suicide account for a large proportion. In drug-facilitated crimes, zolpidem was the most frequently tested component. In 55 case of dog poisonings, the main poisons were cyanides and succinylcholine, and the main poisoning tools were poisonous baits and poisonous syringe darts. ConclusionsThis study profiles the toxicological characteristics of forensic toxicological cases conducted at the AFS in 2021 and provides a scientific basis for poisoning cases and drug abuse prevention.

Lethal and sublethal effects of toxic bait formulations on Doryctobracon areolatus (Hymenoptera: Braconidae) and implications for integrated fruit fly management.

The use of toxic baits has become one of the main methods of management of fruit flies in Brazil. The application of toxic baits may cause side effects on the native parasitoid Doryctobracon areolatus (Hymenoptera: Braconidae). Based on the results, formulations made from the food attractants 3% Biofruit, 1.5% Ceratrap, 1.25% Flyral, 3% Isca Samaritá, 3% Isca Samaritá Tradicional, and 7% sugarcane molasses associated with the Malathion 1000 EC and the ready-to-use toxic bait Gelsura (containing the active ingredient alpha-cypermethrin) were classified as harmful (class 4) to D. areolatus (mortality > 85% at 96 HAE). In contrast, for toxic baits formulated with insecticide phosmet, the mortality ranged from 38% to 72%, classified as slightly harmful or moderately harmful. However, when phosmet was added to the 3% Samaritá Tradicional bait, the mortality was only 3.9% (class 1-harmless), similar to the toxicity observed for the Success 0.02 CB ready-to-use bait (0.24 g a.i. spinosad/l) (<5% mortality). Although toxic baits were formulated with spinosyn-based insecticides, all toxic bait formulations were classified as harmless or slightly harmful (<50% mortality) to D. areolatus, with the exception of 1.5% Ceratrap + spinetoram and 7% Sugarcane molasses + spinosad (≈ 60% mortality-moderately harmful). In addition, these formulations did not show sublethal effects in reducing the parasitism and emergence rate of the F1 generation of D. areolatus in A. fraterculus larvae. The results serve as a basis for the correct use of toxic food baits without affecting the biological control.

The Potential of Fluralaner as a Bait Toxicant to Control Pest Yellowjackets in California.

The western yellowjacket, Vespula pensylvanica (Saussure), is an important seasonal pest of recreational and outdoor venues in the western United States. Its propensity to scavenge food increases the likelihood of stinging incidences. Control measures are limited to intensive trapping and treating subterranean nests. The only toxicant registered for baiting in the US is esfenvalerate, which is ineffective. The objective of this study was to determine the potential of the isoxazoline fluralaner as a bait toxicant. With microsatellite genotyping, a minimum of 27 different colonies were shown to forage at a single monitoring site. Some colonies disappeared after baiting, and new colonies were detected. The implications for baiting and monitoring are discussed. Minced chicken and hydrogel baits containing 0.022% and 0.045% fluralaner significantly reduced foraging yellowjackets. Several bait applications covering large areas will be necessary to provide long-term control.

Laboratory evaluation of the efficacy of deltamethrin-laced attractive toxic sugar bait formulation on Anopheles stephensi

BackgroundAttractive toxic sugar bait (ATSB) is a promising “attract and kill”-based approach for mosquito control. It is a combination of flower nectar/fruit juice to attract the mosquitoes, sugar solution to stimulate feeding, and a toxin to kill them. Selecting an effective attractant and optimizing concentration of toxicant is significant in the formulation of ATSB.MethodsCurrent study formulated an ATSB using fruit juice, sugar and deltamethrin, a synthetic pyrethroid. It was evaluated against two laboratory strains of Anopheles stephensi. Initial studies evaluated comparative attractiveness of nine different fruit juices to An. stephensi adults. Nine ASBs were prepared by adding fermented juices of plum, guava, sweet lemon, orange, mango, pineapple, muskmelon, papaya, and watermelon with 10% sucrose solution (w/v) in 1:1 ratio. Cage bioassays were conducted to assess relative attraction potential of ASBs based on the number of mosquito landings on each and the most effective ASB was identified. Ten ATSBs were prepared by adding the identified ASB with different deltamethrin concentrations (0.015625–8.0 mg/10 mL) in 1:9 ratio. Each ATSB was assessed for the toxic potential against both the strains of An. stephensi. The data was statistically analysed using PASW (SPSS) software 19.0 program.ResultsThe cage bioassays with nine ASBs revealed higher efficacy (p < 0.05) of Guava juice-ASB > Plum juice-ASB > Mango juice-ASB in comparison to rest of the six ASB’s. The bioassay with these three ASB’s ascertained the highest attractancy potential of guava juice-ASB against both the strains of An. stephensi. The ATSB formulations resulted in 5.1–97.9% mortality in Sonepat (NIMR strain) with calculated LC30, LC50, and LC90 values of 0.17 mg deltamethrin/10 mL, 0.61 mg deltamethrin/10 mL, and 13.84 mg deltamethrin/10 mL ATSB, respectively. Whereas, 6.12–86.12% mortality was recorded in the GVD-Delhi (AND strain) with calculated LC30, LC50, and LC90 values of 0.25 mg deltamethrin/10 mL, 0.73 mg deltamethrin/10 mL and 10.22 mg deltamethrin/10 mL ATSB, respectively.ConclusionThe ATSB formulated with guava juice-ASB and deltamethrin (0.0015625–0.8%) in 9:1 ratio showed promising results against two laboratory strains of An. stephensi. Field assessment of these formulations is being conducted to estimate their feasibility for use in mosquito control.

Glucose- and disaccharide-containing baits impede secondary mortality in glucose-averse German cockroaches.

Glucose aversion in the German cockroach, Blattella germanica (L.), results in behavioral resistance to insecticidal baits. Glucose-averse (GA) cockroaches reject foods containing glucose, even in relatively low concentrations, which protects the cockroaches from ingesting lethal amounts of toxic baits. Horizontal transfer of baits and the resulting secondary mortality have been documented in German cockroaches, including in insecticide resistant strains. However, the effects of the GA trait on secondary mortality have not been investigated. We hypothesized that ingestion of insecticide baits that contain glucose or glucose-containing disaccharides would result in behaviorally relevant glucose levels in the feces, possibly deterring coprophagy by GA nymphs. We fed adult female cockroaches hydramethylnon baits rich in either glucose, fructose, sucrose, or maltose and compared secondary mortality of GA and wild-type (WT) nymphs via coprophagy. When adult females were fed baits containing glucose, sucrose, or maltose and their feces offered to nymphs, secondary mortality was significantly lower in GA nymphs than in WT nymphs. However, survival of GA and WT nymphs was similar on feces generated by adult females fed fructose bait. Analysis of feces indicated that disaccharides in baits were hydrolyzed into glucose, some of which was excreted in the feces of females that ingested the bait. Based on these results, we caution that baits containing glucose or glucose-containing oligosaccharides may impede cockroach interventions; while GA adults and large nymphs avoid ingesting such baits, first instars reject the glucose-containing feces of any WT cockroaches that consumed the bait.

The use of toxic baits for the suppression of Mediterranean fruit fly in mango orchards.

Ceratitis capitata (Wiedemann, 1824) is an insect of major economic importance in the mango orchards of the submedium of the São Francisco River Valley, the main area of mango production and exportation in Brazil. To provide alternatives for the management of C. capitata, toxic baits based on alpha-cypermethrin (Gelsura®) and spinosad (Success® 0.02 CB) were evaluated in three commercial mango experiments during two consecutive harvests: 2016/2017 (experiment 1 - area 1) and 2017/2018 (experiment 2 -area 2 and experiment 3 - area 3). According to the results, there was a large reduction in the infestation of C. capitata after five sequential applications of the alpha-cypermethrin (6 g.ha-1) and spinosad (0.38 g.ha-1) toxic baits performed at seven-day intervals during mango fruit ripening in all experiments and years (harvest) evaluated. Compared with the untreated plots, the plots with alpha-cypermethrin and spinosad applications showed a significant reduction in the damage induced (fallen fruits and/or on trees) by C. capitata. The management of C. capitata in mango orchards can include the use of the toxic bait based on alpha-cypermethrin, which represents an alternative to rotate with spinosad toxic bait in the São Francisco River Valley.

Social learning in a nocturnal marsupial: is it a possum-ability?

Social learning can reduce the costs associated with trial-and-error learning. There is speculation that social learning could contribute to trap and bait avoidance in invasive species like the common brushtail possum (Trichosurus vulpecula)-a marsupial for which social learning has not previously been investigated. In large outdoor pens, we presented wild-caught 'demonstrator' possums with puzzle devices containing an attractive food reward; 2 of 8 demonstrators accessed the reward the first night the puzzle was presented and another three succeeded on later nights. Meanwhile, 'observer' possums in adjacent pens watched the demonstrators for five nights and then were given the opportunity to solve the puzzle themselves; 15 of 15 succeeded on their first night (a highly significant improvement). This experiment thus provides strong evidence of social learning by common brushtail possums. Future research should investigate whether information about aversive stimuli (such as traps and toxic baits) can similarly be transmitted between possums by social learning; if so, this could have important implications for possum pest control.

Evaluating predator control using two non-invasive population metrics: a camera trap activity index and density estimation from scat genotyping

Context Invasive mammalian predators are a threat to biodiversity and agriculture globally, yet management outcomes for lethal predator control remain difficult to monitor and evaluate. Understanding whether changes in activity indices correspond to true changes in population density will help inform effective monitoring and management programs. Aims The aim of this study was to evaluate the effect of poison baiting on invasive red fox (Vulpes vulpes) populations using two alternative population metrics: fox activity from camera trap surveys and density estimation from scat genetic analysis. Methods We conducted before–after control–impact studies in two regions of semi-arid Australia (Wimmera and Mallee) by monitoring paired non-treatment and treatment sites during unbaited and baited periods. We estimated the effects of poison baiting on: (1) a monthly fox activity index, derived from an array of 10 off-road camera traps per site; and (2) fox density. To estimate density, we collected fox scats along 14-km transects, identified individuals using polymorphic microsatellite DNA markers and fitted spatially explicit capture–recapture models. Key results Fox activity remained consistently low at all sites except the Mallee non-treatment. The top-ranked models of fox activity and density contained an interaction between treatment and period, with an interactive and additive effect of region, respectively. However, there was little evidence that baiting reduced fox activity or density. In the unbaited period, fox densities ranged from 0.69 (95% CI: 0.47–1.0) to 1.06 (95% CI: 0.74–1.51) foxes km−2 and were similar across regions. Conclusions Camera traps have the potential to provide continuous index-based measures of fox populations but may not record sufficient observations to detect change. Indices can also be confounded by variations in animal behaviour. Scat genetic analysis is a viable option for providing direct estimates of population change at specific snapshots in time; however, this approach is considerably more expensive, and large sample sizes may be required if genotyping success is low. Implications Our study presents a rare example of multiple concurrent – and non-invasive – monitoring techniques to evaluate the effectiveness of predator control. We highlight the value of rigorous study designs and high-quality density information for designing predator management and monitoring programs.

Evaluation of Ziram as an oral toxic bait chemical for control of grass carp Ctenopharyngodon idella

Evaluation of Ziram as an oral toxic bait chemical for control of grass carp Ctenopharyngodon idella

Toxicity and horizontal transfer of bifenthrin and dimefluthrin against the red imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae), and the efficacy of their dust applications in the field

The red imported fire ant, Solenopsis invicta Buren, poses a significant threat to biodiversity, agriculture, and public health in its introduced ranges. While chemicals such as toxic baits and dust are the main methods for S. invicta control, toxic baits are slow, requiring approximately one or two weeks, but dust can eliminate the colony of fire ants rapidly in just three to five days. To explore more active ingredients for fire ant control using dusts, the toxicity of bifenthrin and dimefluthrin, the horizontal transfer of bifenthrin and dimefluthrin dust and their efficacy in the field were tested. The results showed that the LD50 (lethal dose) values of bifenthrin and dimefluthrin were 3.40 and 1.57 ng/ant, respectively. The KT50 (median knockdown time) and KT95 (95% knockdown time) values of a 20 μg mL–1 bifenthrin dose were 7.179 and 16.611 min, respectively. The KT50 and KT95 of a 5 μg mL–1 dimefluthrin dose were 1.538 and 2.825 min, respectively. The horizontal transfers of bifenthrin and dimefluthrin among workers were effective. The mortality of recipients (secondary mortality) and secondary recipients (tertiary mortality) were both over 80% at 48 h after 0.25, 0.50 and 1.00% bifenthrin dust treatments. The secondary mortality of recipients was over 99% at 48 h after 0.25, 0.50 and 1.00% dimefluthrin dust treatments, but the tertiary mortality was below 20%. The field trial results showed that both bifenthrin and dimefluthrin exhibited excellent fire ant control effects, and the comprehensive control effects of 1.00% bifenthrin and dimefluthrin dusts at 14 d post-treatment were 95.87 and 85.70%, respectively.