Alternative Control Methods Research Articles

Attraction of Frankliniella occidentalis Females towards the Aggregation Pheromone Neryl (S)-2-Methylbutanoate and Kairomones in a Y-Olfactometer.

An understanding of insect olfaction allows for more specific alternative methods of pest control. We evaluated the responses of the western flower thrips (WFT, Frankliniella occidentalis) in a Y-olfactometer to estimate gas-phase concentrations of the aggregation pheromone neryl (S)-2-methylbutanoate and known kairomones such as methyl isonicotinate, (S)-(-)-verbenone, and p-anisaldehyde. The gas-phase concentrations of these compounds were obtained from the release rates measured in dynamic headspace cells. The compounds were collected from the headspace using dried solid-phase extraction (SPE) cartridges and analyzed with a triple quadrupole GC-MS/MS. We observed that the aggregation pheromone significantly attracted WFT females at doses of 10 and 100 µg, whereas methyl isonicotinate and p-anisaldehyde significantly attracted WFT females at the highest dose. Verbenone did not produce any significant results. A completely different picture was obtained when the gas-phase concentrations were considered. The minimal gas-phase concentrations of the pheromone required to attract WFT females was 0.027 ng/mL, at least 100 times lower than that of the other two compounds. The relevance and implications of our results are discussed in light of the insect's biology and pest management methods.

Predicted reduction in transmission from deployment of ivermectin-treated birdfeeders for local control of West Nile virus

Ivermectin (IVM)-treated birds provide the potential for targeted control of Culex mosquitoes to reduce West Nile virus (WNV) transmission. Ingestion of IVM increases mosquito mortality, which could reduce WNV transmission from birds to humans and in enzootic maintenance cycles affecting predominantly bird-feeding mosquitoes and from birds to humans. This strategy might also provide an alternative method for WNV control that is less hampered by insecticide resistance and the logistics of large-scale pesticide applications. Through a combination of field studies and modeling, we assessed the feasibility and impact of deploying IVM-treated birdfeed in residential neighborhoods to reduce WNV transmission. We first tracked 105 birds using radio telemetry and radio frequency identification to monitor their feeder usage and locations of nocturnal roosts in relation to five feeder sites in a neighborhood in Fort Collins, Colorado. Using these results, we then modified a compartmental model of WNV transmission to account for the impact of IVM on mosquito mortality and spatial movement of birds and mosquitoes on the neighborhood level. We found that, while the number of treated lots in a neighborhood strongly influenced the total transmission potential, the arrangement of treated lots in a neighborhood had little effect. Increasing the proportion of treated birds, regardless of the WNV competency status, resulted in a larger reduction in infection dynamics than only treating competent birds. Taken together, model results indicate that deployment of IVM-treated feeders could reduce local transmission throughout the WNV season, including reducing the enzootic transmission prior to the onset of human infections, with high spatial coverage and rates of IVM-induced mortality in mosquitoes. To improve predictions, more work is needed to refine estimates of daily mosquito movement in urban areas and rates of IVM-induced mortality. Our results can guide future field trials of this control strategy.

Profitable management of a finite herbicide resource

A financial model of a single farm is used to analyse the profitable management of a finite herbicide supply across time. Delaying resistance can be unprofitable because of the high efficacy and low cost of herbicides, relative to alternative control methods. It is financially attractive to maintain low weed populations, independent of resistance status. Thus, the cost of resistance mainly reflects the need to use more-expensive control options. Non-selective control complements chemical use and extends the susceptibility of weeds to a finite herbicide resource. The model shows that resistance can develop as part of profitable farm management, given the high relative advantage of chemical control. Uncertainty about future herbicide availability, system complexity, temporal volatility, mitigation cost, and short land tenure are primary constraints to efficient herbicide use. This can incur significant costs, through lost profits and accelerated resistance development.

Long-Tailed Macaque (Macaca fascicularis) Contraception Methods: A Systematic Review.

The contraception-based approach to wildlife management is a humane and effective alternative to population control methods. Wildlife management only has a few conventional ways to control overpopulation, such as culling, translocation, poisoning, and allowing natural death. Nevertheless, these methods usually have short-term, lethal, and unethical effects. The present systematic review aims to review the knowledge on contraception reported in long-tailed macaques as an alternative to population control. We obtained 719 records from searching CABI, PubMed, ScienceDirect, and Scopus electronic databases. After the screening and selection process, according to PRISMA guidelines, 19 articles that met the eligibility criteria were chosen. Of the 19 articles, 15 were studies on female long-tailed macaque contraception methods (six (6) hormonal and nine (9) non-hormonal). We analyzed four (4) selected articles on male Cynomolgus monkey contraception methods (two (2) hormonal and two (2) non-hormonal). One of the nine (9) articles on female long-tailed macaque contraception reports negative results. Furthermore, only two (2) studies used free-ranging long-tailed macaques as test subjects, while seventeen (17) tested on captive ones. The challenges of long-tailed macaque contraception identified in this review were the effectiveness of the contraceptive, the administration route, the economic feasibility, the distinction between captive and free-ranging Cynomolgus macaques, the choice of permanent or reversible contraception, the capability of contraceptive use for population control, and the lack of studies on the free-ranging long-tailed macaque. Notwithstanding the literature gap on long-tailed macaque contraception for population control, long-tailed macaque contraception exhibits potential as an alternative method to culling long-tailed macaque. Future research should address these obstacles to support the long-tailed macaque contraception as an alternative population control method.

Biosynthesis, mosquito larvicidal potential, and anticancer activities of gold nanoparticles from Acacia sinuata seed extract

Introduction and Aim: Worldwide, mosquitoes are the main vectors of many deadly diseases like malaria, dengue, chikungunya, etc., Anopheles stephensi mosquito which transmits malaria whereas dengue is transmitted mainly by mosquito Aedes aegypti. Current controlling methods such as chemical or microbial pesticides, repellents, biological control agents against mosquito larvae are not so effective. The leading cause of death worldwide is cancer. Nanotechnology can provide alternative effective methods for malaria, dengue and cancer control, diagnosis and treatment. This study investigated the biosynthesis of gold nanoparticles (AuNPs) from Acacia sinuata seed extract and their mosquito larvicidal potential was tested against Aedes aegypti, Anopheles stephensi larvae. The cytotoxic activity of NPs was also analyzed against human cancer cell lines osteosarcoma (MG-63) and colon adenocarcinoma (Caco-2). Materials and Methods: The biosynthesized NPs were confirmed and characterized by conventional techniques UV- visible spectroscopy, FTIR, XRD, HR-TEM, EDX and SAED. Results: The XRD demonstrated the NPs were face-centred, cubic, and crystalline in nature, EDX study confirmed elemental analysis of gold, SAED illustrated the crystalline nature. The HR-TEM studies revealed NPs shape which were mostly spherical and average size of 5.38nm-8.86nm. Third instar larvae of Aedes aegypti, Anopheles stephensi, were susceptible to the larvicidal effects of AuNPs. The synthesized NPs showed a dose-dependent cytotoxic effect against the Caco-2 and MG-63 cell lines, with IC50 (inhibitory concentrations) of 21.31± 0.15 ug/ml and 86.78± 0.23 ug/ml, respectively. Conclusion: These findings reveal that biosynthesized AuNPs have substantial larvicidal and anticancer properties, suggesting they could be used in mosquito control and cancer treatment.

Microbiota in disease-transmitting vectors.

Haematophagous arthropods, including mosquitoes, ticks, flies, triatomine bugs and lice (here referred to as vectors), are involved in the transmission of various pathogens to mammals on whom they blood feed. The diseases caused by these pathogens, collectively known as vector-borne diseases (VBDs), threaten the health of humans and animals. Although the vector arthropods differ in life histories, feeding behaviour as well as reproductive strategies, they all harbour symbiotic microorganisms, known as microbiota, on which they depend for completing essential aspects of their biology, such as development and reproduction. In this Review, we summarize the shared and unique key features of the symbiotic associations that have been characterized in the major vector taxa. We discuss the crosstalks between microbiota and their arthropod hosts that influence vector metabolism and immune responses relevant for pathogen transmission success, known as vector competence. Finally, we highlight how current knowledge on symbiotic associations is being explored to develop non-chemical-based alternative control methods that aim to reduce vector populations, or reduce vector competence. We conclude by highlighting the remaining knowledge gaps that stand to advance basic and translational aspects of vector-microbiota interactions.

A Review on Fall Armyworm (Spodoptera frugiperda) Insecticide Resistance

The commonly known fall armyworm (Spodoptera frugiperda) is an important pest of corn, cotton, and other crops in the Americas, Africa, and Asia. The species is native to tropical and subtropical regions of the Americas, but it has spread to other parts of the world in recent years. The pest has a wide host range, including important crops like corn, cotton, rice, sorghum, and vegetables. Large populations of fall armyworms can cause significant damage to crops, leading to reduced yields and lower crop quality. The threat of insecticide resistance in S. frugiperda is a growing concern for agricultural production and food security. Insecticides are an important tool for managing fall armyworm populations, but the development of resistance to these chemicals has become a major issue in many regions. This pest has shown resistance to several classes of insecticides, including pyrethroids, organophosphates, and carbamates. To effectively manage insecticide resistance in S. frugiperda populations, it is important to consider these factors and develop integrated pest management strategies that take them into account. This may include the use of alternative control methods, such as biological control and cultural control, and the judicious use of insecticides to minimize selection pressure for resistance development. It is important for farmers, researchers, and policymakers to work together to develop and implement integrated pest management strategies that can effectively manage S. frugiperda populations while minimizing the development and spread of insecticide resistance. Keywords: Fall Armyworm, Spodoptera frugiperda, Insecticide Resistance

Study of the flow structure during the injection of detonation products into the supersonic nozzle

The gradual unloading of the space stage by undocking objects from it or an emer-gency situation due to the undocking of one of the spacecraft leads to mass asymmetry. In outer space there is also the problem of the collision of a space object with elements of space debris. Therefore, the relevance of the topic of this work is determined by the need to develop a system for avoiding the collision of a rocket with elements of space de-bris and controlling the flight, observing the programmed trajectory of movement. The gas-dynamic aircraft system is characterized by the highest speed control. Injection of detonation products into the supercritical part of the nozzle was used as a gas-dynamic system. Modeling was carried out in the SolidWorks application software package. The purpose of the work is to develop alternative methods of the thrust vector control of the upper stage rocket engine. The scheme of the system for the thrust vector control of a rocket engine by the effect of a detonation wave on the gas flow in its nozzle has been developed. The simulation was carried out in a non-stationary flat model at angles to the axis of the combustion chamber of 90°, 60°, 45°, 30° and parallel to the axis, - 0°. The location of the detonation gas generator was near the nozzle section. Numerical simulation revealed that the impact of the detonation wave on the main gas flow in the nozzle causes two power factors. The first force factor is due to the reactive force when detonation products are thrown into the nozzle and on the wall of the high pressure zone where the detonation gas generator is located. The second force factor is due to the change in pressure distribution on the nozzle surface, where high pressure zone creates reflecting on it. The dependence of the relative lateral force on the injection angle of detonation products into the combustion chamber over time has been obtained. The structure of the flow according to the patterns of the velocity distribution in the nozzle during the injection of detonation products is also considered. In cases when the injec-tion is blown at 900 and 450, the release of detonation products initiates a shock wave of high intensity, which moves against the supersonic flow, retarding it. The developed scheme can be used for maneuvering the upper stage of a prospective launch vehicle to avoid its collision with elements of space debris.

Alternative Seed Treatment Methods for Control of Septoria petroselini on Parsley Seed

Septoria leaf blight caused by the fungus Septoria petroselini is one of the major and important diseases in parsley occurring in many countries. The use of high quality seeds is one of the conditions for an efficient crop production. As the fungus is a seedborne, use of clean and certified seeds is important for disease control especially for use in organic farming. Resistance inducers, commercially formulated and non-formulated selected bacterial strains were applied as seed treatments on naturally infested seeds and were tested under controlled and field conditions. Most of these treatments had positive effect on seed germination. Among the seven resistance inducers tested in greenhouse experiments, Jasmonic acid had the best result and increased seed germination by 25.6%. All the three commercial products and the experimental strain Bacillus subtilis K3 increased the number of plants, the yield and decreased the disease incident significantly in field experiments. The experimental bacteria reduced Septoria infection by 70% and increased the yield by 24%. Results indicate that several options for non-chemical control of this pathogen exist and can be recommended for better quality and quantity of the parsley crop production.

Biological control of the pear psylla: studies of its natural enemies and aspects of its chemical communication: Doctoral thesis abstract

The pear psylla, Cacopsylla bidens, is one of the pests that has acquired a primary role in pear cultivation. Finding alternate control methods is required because the management of this hemipteran has relied on the usage of chemical control. To meet this demand, these project aims to improve the understanding of the biology, chemical communication and trophic webs of the predator guild to be able to design a biological control strategy. Molecular approaches were used to determine which of the predators present in the orchard was feeding on C. bidens. Likewise, it was sought to determine at what time of the season these natural enemies begin to act. The findings revealed that many predators from the orders Coleoptera and Neuroptera feed on the pest. Chrysoperla externa was the predator that most frequently fed on C. bidens. In turn, it was determined that these predators begin to act in a more relevant way only on the third generation of C. bidens. To anticipate the arrival of C. externa in the season, it was investigated whether the pear tree changed its volatile profile after being damaged by C. bidens. Likewise, the volatile released following Argyrotaenia sphaleropa damage were identified. The results showed that the pear tree modifies its volatile profile, and this alteration is specific to the herbivore. The predator C. externa was evaluated to determine whether this change could elicit a behavioral response, demonstrating that this predator benefits from the change by discriminating between undamaged plants and plants damaged by both herbivores by being more attracted to volatiles released when the plant is damaged by C. bidens. These finding provides critical information that may be used to move towards a more sustainable management of the pest.

Attraction of Umbelliferone in Snail Attractant Pellets (SAP) against the Snail Lymnaea acuminata: An Intermediate Host of Fasciola gigantica

Snail control method is one of the best ways to management of the fasciolosis. Snail attractant pellets (bait) containing attractant and molluscicide is the good alternative method for control of the Lymnaea acuminata, which is a known intermediate host of Fasciola gigantica. The result of the present study is to find the attraction of molluscicide umbelliferone in snail attractant pellets (SAP) against the Lymnaea acuminata, a vector of snail in different months of the year. Data shows that active molluscicidal component (umbelliferone) showed more attraction at lower concentration. On the contrary, at higher concentration, attraction of snail decreases significantly throughout the year. The attraction of snails declined significantly (P < 0.01) as the concentrations of molluscicide incorporated inside the pellets were increased and water temperature is low (i.e., in winter season). SAP containing 0.5% umbelliferone + starch attract maximum snails (46.0%) and 0.5% umbelliferone + proline, attract maximum snails (42.33%), in the month of June, whereas minimum attraction was observed in the month of January to March when SAP containing 7.0% umbelliferone + starch (6.23-8.1%) and when SAP containing 3.0 % umbelliferone + proline (7.33-9.45%).

Bioinsecticidal efficacy of Eucalyptus camaldulensis (Dehn) and Hyptis suaveolens (L.) Poit. leaf extracts on Callosobruchus maculatus (Cowpea weevil)

The modern method of controlling insect pests, using synthetic insecticides has caused serious problems to human health and the environment. Hence, the need for alternative, cheap, readily available and acceptable insect pest control methods, among which are the use of plant leaf extracts. The aim of this study was to determine the bioinsecticidal efficacy of Eucalyptus camaldulensis and Hyptis suaveolens against cowpea weevils (Callosobruchus maculatus). The bioassay of the powdered methanol extracts of leaves of E. camaldulensis and H. suaveolens was carried varying quantities (3 g, 6 g, 9 g and 12 g) of powdered extracts of the respective plant samples were mixed separately with 50 g of cowpea. Synthetic insecticide, Al2(PO4)3 was used as positive control while the negative control contained no treatment. Proximate compositions of the treated and untreated cowpeas were done using standard procedures while the extracts were characterized using Gas Chromatography-Mass Spectroscopic. Although mortality rates of the C. maculatus in presence of the extracts did not follow any dose-dependant trend, the respective dosages used for treatments inhibited the growth and activities of Callosobruchus maculatus. A high rate of seed damage was observed in the untreated cowpea seeds. Gas Chromatography-Mass Spectroscopy of the extracts identified the presence of seven potential insecticidal compounds (Bargamotene, Globulol, Humulene, Linolein, Prasterone, Terpinen-4-ol and Traumatic acid) in Hyptis suaveolen. In the Eucalyptus camaldulensis extract, 13 potential insecticidal compounds (Barosma camphor, Carvacrol, Carbazon, Irone, Isoborneol, 5-methyl, 1,4-Naphthoquinone, Oleic Acid, Phytol, Piperitone, Pyrazole-3-carboxylic acid, Terpinen-4-ol, Viridiflorol) were identified. The bioinsecticidal activities of these plant extracts could be attributed to the presence of phytochemicals and isolated insecticidal compounds.

Structural and functional insights into the ATP-binding cassette transporter family in the corn planthopper, Peregrinus maidis.

The corn planthopper, Peregrinus maidis, is an economically important pest of maize and sorghum. Its feeding behaviour and the viruses it transmits can significantly reduce crop yield. The control of P. maidis and its associated viruses relies heavily on insecticides. However, control has proven difficult due to limited direct exposure of P. maidis to insecticides and rapid development of resistance. As such, alternative control methods are needed. In the absence of a genome assembly for this species, we first developed transcriptomic resources. Then, with the goal of finding targets for RNAi-based control, we identified members of the ATP-binding cassette transporter family and targeted specific members via RNAi. PmABCB_160306_3, PmABCE_118332_5 and PmABCF_24241_1, whose orthologs in other insects have proven important in development, were selected for knockdown. We found that RNAi-mediated silencing of PmABCB_160306_3 impeded ovary development; disruption of PmABCE_118332_5 resulted in localized melanization; and knockdown of PmABCE_118332_5 or PmABCF_24241_1 each led to high mortality within five days. Each phenotype is similar to that found when targeting the orthologous gene in other species and it demonstrates their potential for use in RNAi-based P. maidis control. The transcriptomic data and RNAi results presented here will no doubt assist with the development of new control methods for this pest.

Computationally Efficient Overmodulation Methods for Synchronous Motor Drive Systems

This article presents two computationally efficient methods for selecting the optimal modulated voltage that can achieve superior dynamic performance for surface-mounted permanent magnet synchronous motors (SPMSMs). Specifically, when an SPMSM suffers a large reference or sudden load change, the controller might command a voltage reference, which is beyond the range of voltages that a modulator can synthesize. In such cases, the transient behavior of the motor can deteriorate when the demanded voltage is not properly limited to the voltage boundary. To address this issue, a simple overmodulation method based on common-mode-saturation injection (CMSI) is proposed. This strategy comes with very low computational cost and can easily find the voltage vector on the boundary, which is nearest to the reference voltage vector. Moreover, an alternative control method, referred to as quadratic program (QP) based deadbeat (DB) control, is proposed that also ensures optimal system performance during overmodualtion. According to this strategy, the control problem is formulated as a constrained QP, which is solved with an efficient solver based on an active-set method. Finally, extensive simulative and experimental investigations for an SPMSM are presented to demonstrate the effectiveness of the proposed overmodulation methods.

Selectivity and Efficacy of Acetic Acid and d-Limonene on Four Aquatic Plants

Most lake, canal, and pond management programs in the United States use herbicides labeled for aquatic use because many of these products, which are registered by the US Environmental Protection Agency, are relatively inexpensive and can effectively control undesirable plants without excessive damage to desirable species. Managers of these resources have expressed an interest in alternative methods for aquatic weed control that could reduce the use of traditional synthetic herbicides. We studied the effects of acetic acid and d-limonene on growth of the invasive aquatic species rotala (Rotala rotundifolia) and crested floatingheart (Nymphoides cristata), as well as on the native wetland plants spatterdock (Nuphar advena) and giant bulrush (Schoenoplectus californicus). We applied acetic acid and d-limonene (alone and in combination) once as foliar treatments to healthy plants, then grew out the plants for 8 weeks after treatment to observe damage resulting from treatments. We also evaluated diquat dibromide at three concentrations as “industry-standard” synthetic treatments for comparison. A 0.22% concentration of diquat dibromide eliminated most or all vegetation of rotala, crested floatingheart, and giant bulrush, but was much less damaging to spatterdock. Single-product applications of acetic acid or d-limonene had little effect on any of the four species evaluated. Some combinations of acetic acid and d-limonene provided acceptable control of rotala and selectivity on spatterdock and giant bulrush, but no treatments reduced crested floatingheart growth by more than 40%. Treating rotala with acetic acid and d-limonene instead of diquat dibromide would result in a 25-fold increase in material costs, which would make this option unaffordable for most aquatic system managers.

Fluxapyroxad Resistance Mechanisms in Sclerotinia sclerotiorum.

The necrotrophic pathogen Sclerotinia sclerotiorum has a global distribution and a wide host range making it one of the most damaging and economically important of all plant pathogens. The current study found that fluxapyroxad, a typical succinate dehydrogenase inhibitor (SDHI) fungicide, had a strong inhibitory effect against S. sclerotiorum, with EC50 values ranging from 0.021 to 0.095 μg/mL. Further investigation of five highly resistant S. sclerotiorum mutants, with EC50 values of 12.37-31.36 μg/mL, found that fluxapyroxad resistance was accompanied by a certain cost to fitness. All of the mutants were found to have significantly (p < 0.05) reduced mycelial growth and altered sclerotia production in artificial culture, as well as reduced pathogenicity compared to wild-type isolates, with one mutant completely losing the capacity to infect detached soybean leaves. Sequence analysis found that four of the mutants had point mutation leading to amino acid changes in the SsSdhB subunit of the fungicide target protein succinate dehydrogenase. In addition, two of the mutants were also found to have amino acid changes in the predicted sequence of their SsSdhD subunit, whilst the fifth mutant had no changes in any of its SsSdh sequences, indicating that an alternative mechanism might be responsible for the observed resistance in this mutant. No cross-resistance was found between fluxapyroxad and any of the other fungicides tested, including tebuconazole, prochloraz, dimethachlone, carbendazim, procymidone, pyraclostrobin, boscalid, fluazinam, fludioxonil, and cyprodinil, which indicates that fluxapyroxad has great potential as an alternative method of control for the SSR caused by S. sclerotiorum, and which could provide ongoing protection to the soybean fields of China.

Вдосконалення інформаційної складової контролю природних монополій

We define the specific features in the control over natural monopoly and the main drawbacks in the contemporary methods of such a control. Also, we analyze some alternative methods of monopoly control that take place in world practice. This paper presents a possible way to improve the information component for quantitative control of natural monopoly using the method of marginal price level fixing (method of price coefficients changing). This method is a widespread one that is used for price regulation of natural monopoly in highly developed countries. However, the method to define the main elements in the corresponding formula — inflation number, economic efficiency factor (X-factor) and effect of external factors (Z-factor) — is still to be elaborated. This fact is one of the main objective reasons why this method is not presently used in practice in Ukraine. Of fundamental importance is the uncertainty of the efficiency factor (X-factor) revision criteria. It can contribute to the slowdown of investments, reducing the interest of the monopolist in large-scale and long-term investments. This paper presents an attempt to eliminate most of the above mentioned drawbacks in the method of the marginal price fixing (method of price coefficients changing) using author's CMI-model of macroeconomic dynamics. We propose a method to define unambiguously the efficiency factor (X) for natural monopoly. Also, we have modified the formula to define the price (tariff) for a product of natural monopoly in order to stimulate the monopoly's innovative and investment activity while keeping the consumer’s interest, and to eliminate the slowdown effect of investments. Besides, using the CMI-model we are able to determine quantitative indexes of monopoly power and the rate of effect of this power on the economy as a whole and on its various sectors. These indexes are proposed as additional ones to the price (tariff) formula to verify the results of the formula’s action.

Specialized Metabolites Produced by Phytotopatogen Fungi to Control Weeds and Parasite Plants.

Weeds such as parasite plants are one of the most serious pests that farmers are forced to combat since the development of agriculture using different methods including mechanic and agronomy strategies. These pests have generated significant losses of agrarian and herding production, constituting a serious impediment for agricultural activities in reforestation practices and in important infrastructures. All these serious problems have induced the expansive and massive use of synthetic herbicides, which represents one of the main cause of environmental pollution, as well as serious risks for human and animal health. An alternative environmental friendly control method could be the use of bioherbicides based on suitably bioformulated natural products, of which the main ones are fungal phytotoxins. This review covers the literature from 1980 to the present (2022) and concerns fungal phytotoxins with potential herbicidal activity in order to obtain their efficacy as bioherbicides for practical application in agriculture. Furthermore, some bioherbicides based on microbial toxic metabolites are commercially available, and their application in field, mode of action and future perspectives are also discussed.

Development of an In Vivo Extended-Spectrum Cephalosporin-Resistant Escherichia coli Model in Post-Weaned Pigs and Its Use in Assessment of Dietary Interventions

Current interventions targeting antimicrobial resistance (AMR), a major impact on commercial pork production, focus on reducing the emergence of AMR by minimising antimicrobial usage through antimicrobial stewardship and a range of alternative control methods. Although these strategies require continued advancement, strategies that directly aim to reduce or eliminate existing antimicrobial resistant bacteria, specifically bacteria resistant to critically important antimicrobials (CIAs), need to be investigated and established. This study established an in vivo model for examining the effects of postbiotics, in the form of Lactobacillus acidophilus fermentation products (LFP) and Saccharomyces cerevisiae fermentation products (SFP), on the shedding of extended-spectrum cephalosporin (ESC)-resistant E. coli. The model was successful in demonstrating the presence of ESC-resistant E. coli as evidenced by its detection in 62 of 64 pigs. There was a strong trend (p = 0.065) for the SFP postbiotics to reduce the shedding of ESC-resistant E. coli, indicating positive impacts of this additive on reducing the carriage of bacteria resistant to CIAs. Overall, this in vivo model enables future evaluation of strategies targeting ESC-resistant E. coli while increasing our knowledge on the carriage of ESC-resistant E. coli in pigs.

Susceptibility of white grubs from forestry and sugarcane plantations in South Africa to entomopathogenic nematodes

The control of white grub (Coleoptera: Scarabaeidae) pests of sugarcane and forest plantations is difficult due to their cryptic nature and resistance to chemicals. This study evaluated the potential use of entomopathogenic nematodes (EPNs) as an alternative control method. Laboratory bioassays were performed with 12 locally isolated EPN species to determine the susceptibility of third instar larvae of the white grubs Schizonycha affinis Boheman, Pegylis sommeri Burmeister, Monochelus sp. and Maladera sp. 4. Concentration trials to determine lethal dosages for three of the white grub species were performed using Heterorhabditis zealandica Poinar MJ2C. Bioassays were performed to determine whether nematodes could develop inside the cadavers of S. affinis and P. sommeri as these had shown the lowest susceptibility to EPNs. The mortality percentage of the white grubs, although varying significantly, was found to be low for most of the EPN species, except H. zealandica. The highest percentage mortality of white grubs was observed at four weeks post inoculation with the rate of mortality being highest in the first week. Schizonycha affinis had the lowest LD50 of 38 Infective juveniles (IJs) per larva after 28 days, compared to Maladera sp. 4, with 284 IJs per larva, and P. sommeri, with 1035 IJs per larva. The dissection of insect cadavers revealed possible limiting factors for low susceptibility, due to the nematodes and their associated symbiotic bacteria’s inability to infect the insect haemocoel, with no EPNs being found inside some of the cadavers.