Effects of single and combined applications of entomopathogenic fungi and nematodes against Rhynchophorus ferrugineus (Olivier)

Compatibility of the fungus Beauveria bassiana and Trichoplusia ni SNPV against the cabbage looper Trichoplusia ni: crop plant matters

BACKGROUND

Microbial insecticides are an important weapon in insect pest management, but their use is still relatively limited. One approach for increasing their efficacy and use could be to combine different pathogens to increase pest mortality. However, little is known about whether increasing pathogen diversity will improve pest management. Here, we investigated the compatibility of two pathogens for the management of the cabbage looper, Trichoplusia ni, T. ni nucleopolyhedrovirus (TniSNPV) and the entomopathogenic fungus Beauveria bassiana, on two crops, tomato and broccoli. The pathogens were applied to individual plants using ultra low volume sprays, alone or in combination, either synchronously or asynchronously. Healthy third-instar T. ni larvae were introduced to the plants before application and collected by destructive sampling 24 h after the last pathogen application.

RESULTS

Combined applications did not result in an increase in larval mortality compared to TniSNPV alone, although mortality was generally high. B. bassiana was considerably less effective on broccoli compared to tomato. In both the combined treatments, virus-induced mortality was approximately 50% lower when applied together with the fungus, while fungus-induced mortality was not affected by the virus, even when the virus was introduced 24 h before the fungus.

CONCLUSION

While our results suggest that applying this combination of entomopathogens would not be beneficial for pest management, this study illustrates the need to consider the target crop as an important driver of the efficacy of both single and mixed pathogen applications in the field. © 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Pest Elaterids of North America: New Insights and Opportunities for Management

The larval stages of click beetle (Coleoptera: Elateridae) species, several of which are serious agricultural pests, are called wireworms. Their cryptic subterranean habitat, resilience, among-species differences in ecology and biology, and broad host range, as well as the lack of objective economic injury thresholds, have rendered wireworms a challenging pest complex to control. Significant progress has been made in recent years, introducing a new effective class of insecticides and improving species identification and our understanding of species-specific phenology, chemical ecology (i.e., adult sex pheromones and larval olfactory cues), and abiotic and biotic factors influencing the efficacy of biological control agents. These new developments have created opportunities for further research into improving our risk assessment, monitoring, and integrated pest management capabilities.

Efficacy of Entomopathogenic Fungi as Prevention against Early Life Stages of the Red Palm Weevil, Rhynchophorus ferrugineus (Coleoptera: Curculionidae) in Laboratory and Greenhouse Trials

The red palm weevil (RPW) Rhynchophorus ferrugineus is a highly destructive invasive pest for palms whose management is mainly by application of synthetic pesticides. As a key pest of date palm plantations, it is necessary to integrate environmentally safe measures for its management. Entomopathogenic fungi (EPF) have been primarily studied as a preventative control measure due to the horizontal transfer of conidia within the RPW population. We previously demonstrated the horizontal transmission of fungal conidia from an egg-laying surface to the female weevil and then to the eggs and larvae. Based on that strategy, this study aimed to evaluate the virulence of commercial EPF products and laboratory EPF preparations to RPW females and their progeny, and their ability to protect palms against infestation. As such, it serves as a screening platform for field experiments. Mortality rates of females and eggs depended on the applied treatment formulation and fungal strain. Velifer®, a Beauveria bassiana product, and Metarhizium brunneum (Mb7) resulted in 60-88% female mortality. Mb7-as a conidial suspension or powder-resulted in 18-21% egg-hatching rates, approximately 3 times less than in the non-treated control. Treating palms with Mb7 suspension or dry formulation significantly inhibits infestation signs and results in protection. These results lay the foundation for investigating the protective rate of EPF products against RPW in date plantations.

Natural Warriors against Stored-Grain Pests: The Joint Action of Beauveria bassiana and Steinernema carpocapsae

Tribolium castaneum, Trogoderma granarium, Oryzaephilus surinamensis, Sitophilus oryzae, Rhyzopertha dominica, and Cryptolestes ferrugineus are all major pests of stored grains. In this study, the efficiency of single and joint applications of the entomopathogenic nematode (EPN) Steinernema carpocapsae at two different doses (50 and 100 IJs cm-2) and the entomopathogenic fungus (EPF) Beauveria bassiana for the management of the aforementioned pests was estimated. At single treatments, both doses of S. carpocapsae caused higher mortality rates to all six pest species compared to B. bassiana. The combined treatment of EPF and EPN resulted in higher mortality compared to single treatments. Mortality was strongly influenced by the exposure interval and the application dose of the EPN at both single and combined treatments. Maximum mortality was observed for the application of the combined treatment at the high dose of S. carpocapsae and B. bassiana. Among the different insect species tested, the maximum mortality rate was observed for R. dominica (96.62%), followed by S. oryzae (90.48%), T. castaneum (87.23%), C. ferrugineus (76.05%), O. surinamensis (70.74%), and T. granarium (57.71%). The outcomes of this study demonstrate the potential of utilizing specific combinations of EPF and EPN as effective natural enemies against stored-grain pests.

Entomopathogen-based biopesticides: insights into unraveling their potential in insect pest management

Global food security is a critical challenge to fulfill the demands of an exponentially growing population. To date, growers rely on chemicals; the broad-spectrum application of synthetic molecules leads to environmental contamination, resistance development, residual toxicity, pest resurgence, and a detrimental effect on human health and cattle. Crop production needs to be improved considering environmental and human health concerns to ensure food security. Furthermore, economically important crops are prone to attack by insect pests, causing considerable yield losses. Microbes are an eco-friendly, versatile alternative, and a potential candidate for combatting destructive pests below the economic injury level and improving the plant's health and productivity. Several microbial pathogens, including parasites, predators, parasitoids, pollinators, and many beneficial microorganisms, possess toxic properties against target organisms but do not cause harm to the non-target organisms. Entomopathogens (ENMs) have great potential for pest suppression due to their remarkable properties. Bacteria are host-specific, but fungi have a broader host range and can be significantly affected by both soil-dwelling and terrestrial insect pests. Virulent pathogens cause mortality in target insect pests known as ENMs and can penetrate through natural openings, ingestions, and integuments to cause a possible effect on target insect pests. The objective of using ENMs is to sustain productivity, improve environmental health, reduce pesticides, and conserve natural resources. Moreover, research is ongoing to discover other possible aspects, especially exploring potential ENMs. Therefore, there is a need for identification, isolation, and bioformulation to overcome the existing issues. This study is mainly focused on the status of bio-formulations, pathogenicity, their mode of action, and the potential application of different types of microbial formulations for sustainable pest management.

Interactions between Entomopathogenic Fungi and Entomopathogenic Nematodes

Entomopathogenic fungi and entomopathogenic nematodes are globally distributed soil organisms capable of infecting and killing a vast variety of insects. Therefore, these organisms are frequently used as biocontrol agents in insect pest management. Both entomopathogenic fungi and nematodes share the soil environment and thus can infest and compete for the same insect host; however, natural co-infections are rarely found due to the cryptic soil environment. Our current knowledge on their interactions within hosts mainly comes from laboratory experiments. Because of the recent trend of combining biocontrol agents to increase their efficacy, many studies have focused on the co-application of different species of EPF and EPNs against various insect pests with variable outcomes ranging from synergistic effects and additive effects to antagonism. In addition, the effect on the development and reproduction of each pathogen varies from normal reproduction to exclusion, and generally the outcomes of the interactions are dependent on pathogen and host species, pathogen doses, and the timing of infection. The present review aims to summarize the current knowledge on the interactions of entomopathogenic fungi and nematodes within an insect host and to estimate the possible effects of the interactions on natural pathogen populations and on their use in biocontrol.

Field Evaluation of Promising Indigenous Entomopathogenic Fungal Isolates against Red Palm Weevil, Rhynchophorus ferrugineus (Coleoptera: Dryophthoridae)

The rate of the sounds (i.e., substrate vibrations) produced by the movement and feeding activity of red palm weevil (RPW) pest infestations in a date palm tree was monitored over time after trees were separately treated with injection of entomopathogenic fungal isolates, Beauveria bassiana and Metarhizium anisopliae, or water treatment as the control. The activity sensing device included an accelerometer, an amplifier, a digital recorder, and a signal transmitter that fed the data to a computer that excluded background noise and compared the rates of bursts of movement and feeding sound impulses among treated trees and controls. Observations were made daily for two months. The rates of bursts were representative of the feeding activity of RPW. The unique spectral pattern of sound pulses was typical of the RPW larval feeding activity in the date palm. The microphone confirmed that the same unique tone was produced in each burst. Two months after fungal injection, the RPW sound signal declined, while the RPW sound signal increased in the control date palms (water injection). The mean rates of bursts produced by RPW decreased to zero after the trees were injected with B. bassiana or M. anisopliae compared with the increased rates over time in the control treatment plants.

Stress-Mediated Responses of Aedes aegypti (Diptera: Culicidae) Larvae When Exposed to Metarhizium brunneum (Hypocreales: Clavicipitaceae) and Toxorhynchites brevipalpis (Diptera: Culicidae)

Aedes aegypti mosquitoes are capable of vectoring a wide range of diseases including dengue, yellow fever, and Zika viruses, with approximately half of the worlds' population at risk from such diseases. Development of combined predator-parasite treatments for the control of larvae consistently demonstrates increased efficacy over single-agent treatments, however, the mechanism behind the interaction remains unknown. Treatments using the natural predator Toxorhynchites brevipalpis and the entomopathogenic fungus Metarhizium brunneum were applied in the laboratory against Ae. aegypti larvae as both individual and combined treatments to determine the levels of interaction between control strategies. Parallel experiments involved the removal of larvae from test arenas at set intervals during the course of the trial to record whole body caspase and phenoloxidase activities. This was measured via luminometric assay to measure larval stress factors underlying the interactions. Combined Metarhizium and Toxorhynchites treatments were seen to drastically reduce lethal times as compared to individual treatments. This was accompanied by increased phenoloxidase and caspase activities in combination treatments after 18 h (p < 0.001). The sharp increases in caspase and phenoloxidase activities suggest that combined treatments act to increase stress factor responses in the larvae that result in rapid mortality above that of either control agent individually. This work concludes that the underlying mechanism for increased lethality in combined parasite-predator treatments may be related to additive stress factors induced within the target host larvae.

Revisiting implementation of multiple natural enemies in pest management

A major goal of biological control is the reduction and/or eradication of pests using various natural enemies, in particular, via deliberate infection of the target species by parasites. To enhance the biological control, a promising strategy seems to implement a multi-enemy assemblage rather than a single control agent. Although a large body of theoretical studies exists on co-infections in epidemiology and ecology, there is still a big gap in modelling outcomes of multi-enemy biological control. Here we theoretically investigate how the efficiency of biological control of a pest depends on the number of natural enemies used. We implement a combination of eco-epidemiological modelling and the Adaptive Dynamics game theory framework. We found that a progressive addition of parasite species increases the evolutionarily stable virulence of each parasite, and thus enhances the mortality of the target pest. However, using multiple enemies may have only a marginal effect on the success of biological control, or can even be counter-productive when the number of enemies is excessive. We found the possibility of evolutionary suicide, where one or several parasite species go extinct over the course of evolution. Finally, we demonstrate an interesting scenario of coexistence of multiple parasites at the edge of extinction.

Integrated Pest Management of Wireworms (Coleoptera: Elateridae) and the Rhizosphere in Agroecosystems

The rhizosphere is where plant roots, physical soil, and subterranean organisms interact to contribute to soil fertility and plant growth. In agroecosystems, the nature of the ecological interactions within the rhizosphere is highly dynamic due to constant disruptions from agricultural practices. The concept of integrated pest management (IPM) was developed in order to promote an approach which is complementary to the environment and non-target organisms, including natural enemies, by reducing the sole reliance on synthetic pesticides to control pests. However, some of the implemented integrated cultural and biological control practices may impact the rhizosphere, especially when targeting subterranean pests. Wireworms, the larval stage of click beetles (Coleoptera: Elateridae), are generalist herbivores and a voracious group of pests that are difficult to control. This paper introduces some existing challenges in wireworm IPM, and discusses the potential impacts of various control methods on the rhizosphere. The awareness of the potential implications of different pest management approaches on the rhizosphere will assist in decision-making and the selection of the control tactics with the least long-term adverse effects on the rhizosphere.

Evaluation of Entomopathogenic Nematodes against Red Palm Weevil, Rhynchophorus ferrugineus (Olivier) (Coleoptera: Curculionidae)

Entomopathogenic nematodes play a pivotal role as biocontrol agents for different species of insect pests, including the red palm weevil. In the current investigation, the infective capabilities of four species of entomopathogenic nematodes, including Hetrerorhabditis bacteriophora, Steinernema feltiae, Steinernema glaseri, and Steinernema carpocapsae, were evaluated against larvae, pupae, and adult red palm weevil under laboratory and field conditions. The pathogenic potential of selected nematode species was assessed based on dissection and adult emergence of weevils. Our results indicated that S. carpocapsae and H. bacteriophora, with a respective 94.68 and 92.68% infection rate, were the most effective EPN species against red palm weevil larvae. Focusing on adult emergence, the aforementioned EPNs were comparatively less pathogenic and resulted in 63.60 and 60.20% infested pupae, respectively. It is noted that adult emergence is the better option to evaluate the pathogenic potential of EPNs, compared with the dissection of insects. The S. carpocapsae was found to be most effective against the 6th instar larvae of the red palm weevil and caused 100% mortality at 240 h after treatment. On the other hand, S. glaseri and S. feltiae were found to be the least pathogenic and caused 70 and 76% mortality, respectively. All of the evaluated nematode species were found to be highly infective under field conditions. The S. carpocapsae was found to be the most pathogenic, causing 83.60% mortality of the red palm weevil. However, the tested nematodes were found most effective against larvae, followed by adult weevils, but their effect was minimal against the pupae of red palm weevils. Based on these findings, we conclude that the S. carpocapsae and H. bacteriophora could be used as a sustainable option for the efficient management of the red palm weevil.

Combined application of entomopathogenic nematodes and fungi against fruit flies, Bactrocera zonata and B. dorsalis (Diptera: Tephritidae): laboratory cups to field study

BACKGROUND

The peach fruit fly, Bactrocera zonata, and the Oriental fruit fly, B. dorsalis (Diptera: Tephritidae), are economically important fruit fly species in various regions of the world. We evaluated the effects of separate and combined applications of the entomopathogenic fungi (EPF) Beauveria bassiana (WG-18) and Metarhizium anisopliae (WG-02), and the entomopathogenic nematodes (EPNs) Heterorhabditis bacteriophora (VS strain) and Steinernema carpocapsae (ALL strain) against larvae, pupae and pharate adults, of B. zonata and B. dorsalis under laboratory, glasshouse and field cage conditions.

RESULTS

Combined applications of EPF and EPNs produced greater mortality than individual treatments under all conditions. Against both species, the combination of B. bassiana and H. bacteriophora consistently exerted strong effects that were similar to the combined application of B. bassiana and S. carpocapsae whereas M. anisopliae applied with S. carpocapsae was least effective in all combinations. In a laboratory bioassay, synergistic interactions were detected between B. bassiana and H. bacteriophora applied against larvae and pharate adults of both fly species, between B. bassiana and S. carpocapsae against larvae of both species and pharate adults of B. zonata, and between M. anisopliae and H. bacteriophora against B. zonata larvae. Other combined treatments resulted in additive effects, especially against fly pupae. In a potted soil bioassay, there were only additive interactions in all combinations against different stages of both flies. The 3rd instar of both flies was more susceptible than pharate adult and pupal stages. Additive interactions between EPNs and EPF were detected in the glasshouse against 3rd instars and pupae, and under field conditions against 3rd instars of both fly species.

CONCLUSION

These results indicate how particular combinations of entomopathogenic fungi and nematodes could be deployed in integrated pest management of tephritid fruit flies in orchard agro-ecosystems. © 2022 Society of Chemical Industry.

A Review of Entomopathogenic Nematodes as a Biological Control Agent for Red Palm Weevil, Rhynchophorus ferrugineus (Coleoptera: Curculionidae)

Rhynchophorus ferrugineus (Olivier) (Coleoptera: Curculionidae) is a severe pest of palm trees worldwide. The development and feeding activities of R. ferrugineus larvae inside the trunk damage palm trees. However, the absence of noticeable infestation signs at an early stage contributes to the spread of the attack. Integrated pest management (IPM) has been introduced to control R. ferrugineus infestation by implementing various approaches and techniques. The application of chemical pesticides has shown impressive results. However, biological control should be applied as an alternative solution due to adverse environmental impacts and pest resistance issues. One example is the use of entomopathogenic nematodes (EPNs) as biological control agents, which can forage and attack targeted pests without compromising the environment and other nontarget organisms. EPNs and their symbiotic bacteria have a mutualistic interaction that can kill the host within a short period of time. Therefore, this review emphasizes the effectiveness of entomopathogenic nematodes and their symbiotic bacteria against R. ferrugineus.

Overview and future research needs for development of effective biocontrol strategies for management of Bactrocera dorsalis Hendel (Diptera: Tephritidae) in sub-Saharan Africa

Infestation of fruits by native and invasive fruit flies causes significant economic losses. In most cases, incidence of 'regulated' dangerous fruit flies in orchards results in restrictions on export of fruits from such places to international markets. Unfortunately, use of insecticides applied on foliage and fruits does not kill the fruit-to-soil stages of fruit flies. However, diverse biological control agents (BCAs) do so. Thus, prevalence of native and invasive fruit flies in orchards will require that a combination of BCAs is included in integrated pest management (IPM) programmes. In the case of Bactrocera dorsalis Hendel and other economically important fruit flies found in sub-Saharan Africa (SSA), use of classical biocontrol approach involves concomitant releases of two exotic parasitoids (Fopius arisanus Sonan and Diachasmimorpha longicaudata Ashmead). These non-native wasps may have complemented the indigenous parasitoids in combination with application of entomopathogenic fungi (EPFs) and conservation of predatory ants (Oecophylla longinoda Latreille, with O. smaragdina) in fruit fly IPM plans. Consequently, some levels of decline in fruit infestation have been observed. Although interspecific interactions between BCAs against several insect pests have produced varying results, including threatening the survival of other BCAs, the prevalence of B. dorsalis in orchards across SSA requires further research to investigate effects of coalescing biocontrol approaches in IPM strategies. Therefore, future research into combining parasitoids, EPFs and entomopathogenic nematodes, in addition to conservation of predatory ants (O. longinoda, O. smaragdina and others) in IPM plans may improve the effectiveness of currently used strategies for the management of fruit-infesting tephritids. © 2021 Society of Chemical Industry.

Model Application of Entomopathogenic Fungi as Alternatives to Chemical Pesticides: Prospects, Challenges, and Insights for Next-Generation Sustainable Agriculture

In the past few decades, the control of pests and diseases of cultivated plants using natural and biological measures has drawn increasing attention in the quest to reduce the level of dependence on chemical products for agricultural production. The use of living organisms, predators, parasitoids, and microorganisms, such as viruses, bacteria, and fungi, has proven to be a viable and sustainable pest management technique. Among the aforementioned, fungi, most importantly the insect-pathogenic species, have been in use for more than 150years. These include the most popular strains belonging to the genera Beauveria, Metarhizium, Isaria, Hirsutella, and Lecanicillium. Their application is usually through an inundative approach, which inherently involves exposure of the fungal spores to unfavorable humidity, temperature, and solar radiation conditions. These abiotic factors reduce the persistence and efficacy of these insect-pathogenic fungi. Despite these limitations, over 170 strains have been formulated as mycopesticides and are available for commercial use. In the last few decades, numerous studies have suggested that these species of entomopathogenic fungi (EPF) offer far more benefits and have broader ecological functions than hitherto presumed. For instance, aside from their roles as insect killers, it has been well established that they also colonize various host plants and, hence, provide other benefits including plant pathogen antagonism and plant growth promotion and serve as sources of novel bioactive compounds and secondary metabolites, etc. In this light, the potential of EPF as alternatives or perhaps as supplements to chemical pesticides in plant protection is discussed in this review. The paper highlights the numerous benefits associated with endophytic fungal entomopathogen and host plant associations, the mechanisms involved in mediating plant defense against pests and pathogens, and the general limitations to the use of EPF in plant protection. A deeper understanding of these plant host-fungus-insect relationships could help unveil the hidden potentials of fungal endophytes, which would consequently increase the level of acceptance and adoption by users as an integral part of pest management programs and as a suitable alternative to chemical inputs toward sustainable crop production.

Evaluation of Locally Isolated Entomopathogenic Fungi against Multiple Life Stages of Bactrocera zonata and Bactrocera dorsalis (Diptera: Tephritidae): Laboratory and Field Study

Fruit flies including Bactrocera zonata and B. dorsalis (Diptera: Tephritidae) are considered major pests of orchard systems in Pakistan. This study evaluated the laboratory virulence, sub-lethal effects, horizontal transmission, greenhouse, and field-cage efficacy of locally isolated entomopathogenic fungi (EPF) against B. zonata and B. dorsalis. In virulence assays against third instars and adults, all 21 EPF isolates (Beauveria bassiana and Metarhizium anisopliae) tested were pathogenic and caused varying levels of mortality to the fruit flies. Based on the initial screening, four isolates (B. bassiana WG-21 and WG-18 and M. anisopliae WG-07 and WG-02) were selected for further study. The isolate WG-18 was the most virulent against larvae and adults of B. zonata and B. dorsalis followed by WG-21, WG-02, and WG-07. In both species, adults were more susceptible than larvae to all isolates, and pupae were the least susceptible. Isolates WG-18 and WG-21 strongly decreased female fecundity and fertility, the highest adult and larval mortality, and longest developmental time of larvae and pupae. Fungal conidia were disseminated passively from infected to healthy adults and induced significant mortality, particularly from infected males to non-infected females. In greenhouse and field-cage experiments, WG-18 and WG-21 were the most effective isolates in reducing adult emergence when applied to larvae and pupae of both fruit fly species. Our results indicate that B. bassiana isolates WG-18 and WG-21 were the most virulent against multiple life stages of B. zonata and B. dorsalis, and also exerted the strongest sub-lethal effects.

Comparative study of the ditrophic interaction between Beauveria bassiana and Plutella xylostella

In the present investigation, hyperparasitic interaction between B. bassiana, TM (MH590235) and P. xylostella was studied through scanning electron microscopy and chromatographic techniques. Dose-mortality responses showed an increase in mortality of larva with an increase in spore concentration. The LC₅₀ value for B. bassiana isolate TM (MH590235) was 2.4 × 10⁷ spores mL^-1. The ditrophic interaction between B. bassiana and P. xylostella after 24 h revealed the adherence of conidia on stemmata, sensory setae, maxillary palpi and legs. After 48 h post-infection (hpi), germination of the conidia and appressorium formation was observed. Formation of hyphae and initiation of fungal networking was observed at 72 hpi. Complete ramification by mycelia and conidiogenesis of B. bassiana was observed over the mycosed cadaver after 168 hpi. Subsequently, typical sympodial conidiophores of B. bassiana bearing secondary spores were also observed. The metabolome profile of healthy larvae of P. xylostella revealed the presence of non-volatile organic compounds (NVOCs) like docosene, nonadecene, palmitic acid and heneicosane. However, the NVOC profile was different in the P. xylostella larvae hyperparasitized by B. bassiana. The metabolites present in the infected cadaver were phthalate esters, hydroxyquebrachamine and lactones.

Virulence of Entomopathogenic Fungi to Rhagoletis pomonella (Diptera: Tephritidae) and Interactions With Entomopathogenic Nematodes

The objectives of this study were to quantify the virulence of four entomopathogenic fungal species to pupae of Rhagoletis pomonella (Walsh) (Diptera: Tephritidae) and to determine the potential to combine entomopathogenic fungi (EPFs) and entomopathogenic nematodes (EPNs) for biological control of this pest. The four species of EPFs included Beauveria bassiana (strain GHA), Metarhizium brunneum (strain F52), Isaria javanica (wf GA17), and Isaria fumosorosea (Apopka 97 strain). In laboratory assays, all fungi reduced adult emergence but there were no differences between fungal species. Isaria javanica and M. brunneum were examined further in a EPFs and EPNs bioassay that also included the EPNs Steinernema carpocapsae (ALL strain) and S. riobrave (355 strain). All nematodes and fungi were applied either alone or in combination (fungus + nematode). There were no differences between species within the same entomopathogen group (fungi and nematodes). However, the treatment with S. riobrave resulted in lower R. pomonella emergence than either fungal species. The combination of S. riobrave and I. javanica resulted in the lowest R. pomonella emergence (3%) at fourth-week interval, which was significantly lower than any of the single-agent applications, yet virulence of the other three combination treatments was not different from their respective nematode treatments applied alone. Additive interactions were detected for all fungus-nematode combinations. This study suggests that application of entomopathogenic nematodes and fungi could be an effective option to suppress R. pomonella populations.

Antiparasitics in Animal Health: Quo Vadis?

Antiparasitics acting on endo- or ectoparasites represent the second largest segment of the global animal health market, accounting for 23% of market share. However, relatively few novel antiparasitic agents have been introduced into the market during recent decades. One exception, and a groundbreaking 21st century success story, are the isoxazolines, whose full potential has not yet been entirely explored. Unfortunately, resistance issues are present across most parasitic diseases, which generates a clear market need for novel resistance-breaking antiparasitics with new modes/mechanisms of action. Recent advances in science and technologies strongly suggest that the time is right to invest in new modalities such as parasitic vaccines or in environmentally friendly interventions.

Assessing immunocompetence in red palm weevil adult and immature stages in response to bacterial challenge and entomopathogenic nematode infection

Parasites and pathogens can follow different patterns of infection depending on the host developmental stage or sex. In fact, immune function is energetically costly for hosts and trade-offs exist between immune defenses and life history traits as growth, development and reproduction and organisms should thus optimize immune defense through their life cycle according to their developmental stage. Identifying the most susceptible target and the most virulent pathogen is particularly important in the case of insect pests, in order to develop effective control strategies targeting the most vulnerable individuals with the most effective control agent. Here, we carried out laboratory tests to identify the most susceptible target of infection by infecting different stages of the red palm weevil Rhynchophorus ferrugineus (larvae, pupae, male, and female adults) with both a generic pathogen, antibiotic-resistant Gram-negative bacteria Escherichia coli XL1-Blue, and two specific strains of entomopathogenic nematodes (EPNs), Steinernema carpocapsae ItS-CAO1 and Heterorhabditis bacteriophora ItH-LU1. By evaluating bacterial clearance, host mortality and parasite progeny release, we demonstrate that larvae are more resistant than adults to bacterial challenge and they release less EPNs progeny after infection despite a higher mortality compared to adults. Considering the two EPN strains, S. carpocapsae was more virulent than H. bacteriophora both in terms of host mortality and more abundant progeny released by hosts after death. The outcomes attained with unspecific and specific pathogens provide useful information for a more efficient and sustainable management of this invasive pest.

Integration of Entomopathogenic Fungi into IPM Programs: Studies Involving Weevils (Coleoptera: Curculionoidea) Affecting Horticultural Crops

Weevils are significant pests of horticultural crops and are largely managed with insecticides. In response to concerns about negative impacts of synthetic insecticides on humans and the environment, entomopathogenic fungi (EPF) have been developed as an alternative method of control, and as such appear to be "ready-made" components of integrated pest management (IPM) programs. As the success of pest control requires a thorough knowledge of the biology of the pests, this review summarises our current knowledge of weevil biology on nut trees, fruit crops, plant storage roots, and palm trees. In addition, three groups of life cycles are defined based on weevil developmental habitats, and together with information from studies of EPF activity on these groups, we discuss the tactics for integrating EPF into IPM programs. Finally, we highlight the gaps in the research required to optimise the performance of EPF and provide recommendations for the improvement of EPF efficacy for the management of key weevils of horticultural crops.

Pathogenic post-effect of entomopathogenic fungi on phytophagous pests and entomophagous biocontrol agents

Phytosanitary optimization of agricultural ecosystems under conditions of glasshouses and organic farming urgently demands guaranteed effect of plant protection. This can be achieved only through effective exploitation of a complex of biological agents, including arthropod predators and parasites, entomopathogenic fungi, nematodes and other microbes. Entomopathogenic fungi Beauveria bassiana and Lecanicillium muscarium are characterized by facultative parasitism and possess high potential to control phytophagous insects, including pests of vegetable crops in glasshouses. In aphids, fungal pathogenesis was found to be comprised of primary mycosis and toxigenic post-effect in a row of consequent generations. For example, L. muscarium and B. bassiana had an adverse effect on fertility and survival rates of females of aphids Aphis gossypii up to the fifth generation. The longevity, reproductive period and amount of progeny were decreased in aphids treated with water suspension of fungal conidia. It can be deduced that the post-effect is caused by toxic action of metabolites as no evident mycosis was observed in the experiments. Similar type of after-effect is observed in the lacewing Chrysopa carnea contaminated with fungal conidia. The effect is also toxigenic being most prominent in the first generation of the survivors’ progeny and traceable up to the fifth generation. The consequences of the infection are best seen in the rate adult emergence which is twice as low as compared to control. This knowledge is essential to avoid antagonism between different groups of natural enemies exploited in biological control and to design adequate technology for their application.

Mortality of Phyllophaga vetula larvae by the separate and combined application of Metarhizium anisopliae, Steinernema carpocapsae and Steinernema glaseri

Phyllophaga spp. are a complex of edaphic insect pests that are present in the corn crops (Zea mays) in México, which are usually controlled with increasing dosages of broad-spectrum chemical insecticides. Several entomopathogenic nematode species can produce acceptable control levels of these larvae. However, the synergistic interaction between fungi and entomopathogenic nematodes (EPN) could improve the control of this insect. This study investigates the mortality of larvae of Phyllophaga vetula by the effect of the separate or combined application of the fungus Metarhizium anisopliae M1cog strain (Ma) and the nematodes Steinernema carpocapsae All strain (Sc) or Steinernema glaseri NJ-43 strain (Sg). In laboratory, dosages of 1 × 106 or 1 × 108 spores/larva and 250 infective juveniles were applied on medium or large size P. vetula larvae contained in vials with sterilized agricultural soil as the assay arena. The separate application of Ma did not kill any larvae, but Sg and Sc killed 40 and 80% of the larvae, respectively. However, the Ma and Sc combination had an important antagonistic interaction that decreased the mortality to 40%, but the combination Ma and Sg had a slight additive interaction that increased the mortality to 47%. The most determining factor in larvae mortality was the nematode used, with Sg as the species with best performance in 6 of the 12 treatments evaluated and with a maximum effectivity of 80% on medium-size larvae if combined with a low dosage of Ma. The combined application of an entomopathogenic fungus and EPN showed no consistent effects on the mortality percentage of P. vetula, mostly because the fungus was not isolated from Phyllophaga larvae.

The symbiotic bacteria Alcaligenes faecalis of the entomopathogenic nematodes Oscheius spp. exhibit potential biocontrol of plant- and entomopathogenic fungi

Soil-dwelling entomopathogenic nematodes (EPNs) kill arthropod hosts by injecting their symbiotic bacteria into the host hemolymph and feed on the bacteria and the tissue of the dying host for several generations cycles until the arthropod cadaver is completely depleted. The EPN-bacteria-arthropod cadaver complex represents a rich energy source for the surrounding opportunistic soil fungal biota and other competitors. We hypothesized that EPNs need to protect their food source until depletion and that the EPN symbiotic bacteria produce volatile and non-volatile exudations that deter different soil fungal groups in the soil. We isolated the symbiotic bacteria species (Alcaligenes faecalis) from the EPN Oscheius spp. and ran infectivity bioassays against entomopathogenic fungi (EPF) as well as against plant pathogenic fungi (PPF). We found that both volatile and non-volatile symbiotic bacterial exudations had negative effects on both EPF and PPF. Such deterrent function on functionally different fungal strains suggests a common mode of action of A. faecalis bacterial exudates, which has the potential to influence the structure of soil microbial communities, and could be integrated into pest management programs for increasing crop protection against fungal pathogens.