Control Of Insect Populations Research Articles

Sex-specific transgenerational effects on murine thyroid gland imposed by ancestral exposure to neonicotinoid thiacloprid

Neonicotinoids, a relatively new widely used class of insecticide is used in agriculture to control insect populations. We examined the capacity of ancestral exposure to the neonicotinoid thiacloprid (thia) to induce transgenerational effects on thyroid tissue. Pregnant outbred Swiss female mice were exposed to thia at embryonic days E6.5 to E15.5 using 0, 0.6, and 6 mg/kg/day doses. Thyroid paraffin sections were prepared for morphology analysis. We apply ELISA method to measure T4 and TSH levels, RT-qPCR for gene expression analysis, ChIP-qPCR techniques for sperm histone H3K4me3 analysis, and immunofluorescence microscopy and western blots for protein detection. We observed an alteration in the morphology of thyroids in both males and females in the F3 generation. We observed an increase in T4 hormone in F1 females and a significant T4 level decrease in F3 males. T4 changes in F1 females were associated with a TSH increase. We found that the amount of Iodothyronine Deiodinase 1 (DIO1) (an enzyme converting T4 to T3) was decreased in both F1 and F3 generations in female thyroids. GNAS protein which is important for thyroid function has increased in female thyroids. Gene expression analysis showed that the expression of genes encoding thyroid gland development, chromatin, biosynthesis and transport factors were affected in the thyroid gland in both sexes in F1 and F3. The analysis of sperm histone H3K4me3 showed that H3K4me3 occupancy at the Dio1 locus has decreased while Thyroglobulin (Tg) and Matrix Metallopeptidase 2 (Mmp2) genes have increased H3K4me3 occupancy in the sperm of F3 mice. Besides, DNA methylation analysis of our previously published datasets showed that, in the sperm of F1 and F3 thia-derived mice, several genes related to thyroid function show consistent alterations. Our data suggest that ancestral exposure to thiacloprid affects thyroid function not only in exposed but also in indirectly exposed F3 generation.

Turmeric shortens lifespan in houseflies.

Climate change poses a significant threat to food security and global public health with the increasing likelihood of insect pest outbreaks. Alternative ways to control insect populations, preferably using environmental-friendly compounds, are needed. Turmeric has been suggested as a natural insecticide with toxicity properties in some insect groups. However, empirical evidence of the effects of turmeric - and their interaction with other ecological factors such as diet - on insect survival has been limited. Here, we tested the effects of turmeric and its interactions with diets differing in protein source in the common housefly, Musca domestica. We found that turmeric shortened lifespan independent of diet and sex. Females in turmeric diets were heavier at death, which was likely driven by a combination of relatively lower rates of body mass loss during their lifetime and a higher percentage of water content at death. Each sex responded differently to the protein source in the diet, and the magnitude of the difference in lifespan between sexes were greatest in diets in which protein source was hydrolysed yeast; individuals from both sexes lived longest in sucrose-milk diets and shortest in diets with hydrolysed yeast. There was no evidence of an interaction between turmeric and diet, suggesting that the toxicity effects are independent of protein source in the diet. Given the seemingly opposing effects of turmeric in insects and mammals being uncovered in the literature, our findings provide further evidence in support of turmeric as a potential natural insecticide.

Patch exploitation behaviour by a parasitoid of a forest pest: The influence of host cues and intra‐ and interspecific interactions

Abstract For parasitoids, host foraging is the most significant activity for their reproductive success, as it directly translates into offspring production. Therefore, foraging behaviour and patch‐use decisions by parasitoids still attract research interest, especially when the studied species are biological control agents. In laboratory conditions, we studied the patch exploitation behaviour of Megarhyssa nortoni (Hymenoptera: Ichneumonidae), a larval–pupal parasitoid of several woodwasps (Hymenoptera: Siricidae), exposed to intra‐ and interspecific interactions. It is known that M. nortoni females are attracted to the symbiotic fungus carried by its hosts, which support host larval development inside the wood. Additionally, in the introduced range where the species has been released in biocontrol programs aimed at managing invasive Sirex noctilio populations, Megarhyssa nortoni coexists with the egg–larval parasitoid Ibalia leucospoides. First, we investigated whether host–fungal symbiont cues and direct presence of conspecific females affected patch time allocation and oviposition behaviour of M. nortoni, as both stimuli could provide information on concealed hosts. Second, we studied the influence of prior parasitism by I. leucospoides on patch time allocation decisions and oviposition behaviour. The main results showed that females modulated their responses to the fungal cues when foraging simultaneously with conspecifics. Also, patch‐leaving tendencies and patch residence times were not affected when females foraged patches previously exploited by I. leucospoides; indeed, they probed these patches more frequently. Our study contributes to the understanding of patch‐use decisions made by parasitoids and their impact on the biological control of damaging insect populations, particularly in a context of two parasitoid species and one host.

Doxycycline is a viable alternative to tetracycline for use in insect Tet-Off transgenic sexing systems, as assessed in the blowflies Cochliomyia hominivorax and Lucilia cuprina (Diptera: Calliphoridae).

Transgenic insect strains with tetracycline repressible (Tet-Off) female-lethal genes provide significant advantages over traditional sterile insect techniques for insect population control, such as reduced diet and labor costs and more efficient population suppression. Tet-Off systems are suppressed by tetracycline-class antibiotics, most commonly tetracycline (Tc) or doxycycline (Dox), allowing for equal sex ratio colonies of transgenic insects when reared with Tc or Dox and male-only generations in their absence. Dox is a more stable molecule and has increased uptake than Tc, which could be advantageous in some insect mass-rearing systems. Here, we evaluated the suitability of Dox for rearing Tet-Off female-lethal strains of Australian sheep blowfly, Lucilia cuprina (Wiedemann, 1830) (Diptera: Calliphoridae), and New World screwworm, Cochliomyia hominivorax (Coquerel, 1858) (Diptera: Calliphoridae), and the effects of dosage on strain performance. For both species, colonies were able to be maintained with mixed-sex ratios at much lower dosages of Dox than Tc. Biological yields of C. hominivorax on either antibiotic were not significantly different. Reduction of Dox dosages in C. hominivorax diet did not affect biological performance, though rearing with 10 or 25 μg/mL was more productive than 50 μg/mL. Additionally, C. hominivorax mating performance and longevity were equal on all Dox dosages. Overall, Dox was a suitable antibiotic for mass-rearing Tet-Off female-lethal L. cuprina and C. hominivorax and was functional at much lower dosages than Tc.

EFFECTS OF Azadirachta indica, Parkia biglobosa AND SYNTHETIC INSECTICIDES ON Sesamia calamistis (HAMPSON) ON GROWTH AND YIELD OF MAIZE (Zea Mays L.) IN MAKURDI

Zea mays, plays a crucial role in the dietary habits of numerous individuals residing in Nigeria. Several factors, including the presence of Sesamia calmistis and the effects of synthetic insecticides on beneficial insects and hazards to humans, contribute to the limitation of maize output. The study evaluated the effect of Azadirachta indica and Parkia biglobosa extracts on the control of S. calamistis and this experiment was carried out in two planting seasons of 2021 and 2022. The experiment was carried out at the Teaching and Research Farm, Joseph Sarwuan Tarka University, Makurdi. Three treatments; A. indica, P. biglobosa, Karate 5 EC (Lambda cyhalothrin 5 EC) and control were used. From the study, A. indica extract had a significant effect at p<0.05 on the insect population resulting in a significant increase in the yield parameters which includes the number 100 seed weight of the plant, yield in both 2021 and 2022 planting season with the mean value of 5298.21 and 5428.98 kg/ha respectively. The use of A. indica extract was observed to be effective in the control of insect population and leading to maximum productivity of maize low infestation by observing the maize plant with borers tunnels to be lower in A. indica extracts and Karate 5 EC plots with the mean value of 3.00 and 3.00 in 2021 planting season respectively at p<0.05. The percentage of dead hearts at 60 days after treatment in 2021 and 2022 cropping seasons was significant at p<0.05%, with the control plot having the highest...

Genetic diversity of Metarhizium sp. isolated from various hosts in East Dumoga, North Sulawesi, Indonesia

Abstract. Siahaan P, Mangais RER, Kolondam B, Tangapo A, Mambu S. 2023. Genetic diversity of Metarhizium sp. isolated from various hosts in East Dumoga, North Sulawesi, Indonesia. Biodiversitas 24: 6888-6896. Metarhizium fungus is an entomopathogenic fungus known to kill many insect pests. This means that Metarhizium sp. has an important ecological role in the ecosystem, especially in controlling insect populations and recycling nutrients. Studying the genetic diversity of Metarhizium species and their relationships with insect hosts provides insight into pest management and the study of their taxonomy. The study aimed to investigate the genetic variability among Metarhizium fungi by examining their respective host types, which can be used as basic data for taxonomic studies, germplasm conservation efforts, and pest management. Exploration results showed that three insect species were infected with the Metarhizium sp fungus, namely Scotinophara coarctata, Nilaparvata lugens, and Recilia dorsalis. The results of a phylogenetic analysis has shown that the S. coarctata isolate was in the same group as four comparable Metarhizium anisopliae isolates from GenBank with a similarity level of 100%, while the N. lugens and R. dorsalis isolates were in the same group as four Metarhizium huainamdangense isolates with a similarity level. 99% and three isolates of Metarhizium flavoviride with 98% similarity. Molecular analysis confirmed that the Metarhizium isolated from S. coarctata was the M. anisopliae species, while those isolated from N. lugens and R. dorsalis were the M. huainamdangense species. Differences in host insects have been proven to provide genetic variation to the Metarhizium sp. fungus.

Cross-talk between immunity and behavior: insights from entomopathogenic fungi and their insect hosts.

Insects are one of the most successful animals in nature, and entomopathogenic fungi play a significant role in the natural epizootic control of insect populations in many ecosystems. The interaction between insects and entomopathogenic fungi has continuously coevolved over hundreds of millions of years. Many components of the insect innate immune responses against fungal infection are conserved across phyla. Additionally, behavioral responses, which include avoidance, grooming, and/or modulation of body temperature, have been recognized as important mechanisms for opposing fungal pathogens. In an effort to investigate possible cross-talk and mediating mechanisms between these fundamental biological processes, recent studies have integrated and/or explored immune and behavioral responses. Current information indicates that during discrete stages of fungal infection, several insect behavioral and immune responses are altered simultaneously, suggesting important connections between the two systems. This review synthesizes recent advances in our understanding of the physiological and molecular aspects influencing cross-talk between behavioral and innate immune antifungal reactions, including chemical perception and olfactory pathways.

Gene drive and genetic sex conversion in the global agricultural pest Ceratitis capitata

Homing-based gene drives are recently proposed interventions promising the area-wide, species-specific genetic control of harmful insect populations. Here we characterise a first set of gene drives in a tephritid agricultural pest species, the Mediterranean fruit fly Ceratitis capitata (medfly). Our results show that the medfly is highly amenable to homing-based gene drive strategies. By targeting the medfly transformer gene, we also demonstrate how CRISPR-Cas9 gene drive can be coupled to sex conversion, whereby genetic females are transformed into fertile and harmless XX males. Given this unique malleability of sex determination, we modelled gene drive interventions that couple sex conversion and female sterility and found that such approaches could be effective and tolerant of resistant allele selection in the target population. Our results open the door for developing gene drive strains for the population suppression of the medfly and related tephritid pests by co-targeting female reproduction and shifting the reproductive sex ratio towards males. They demonstrate the untapped potential for gene drives to tackle agricultural pests in an environmentally friendly and economical way.

Spider diversity in different habitats at District Mardan, Khyber Pakhtunkhwa Pakistan.

Spider species are important for maintaining ecological balance, controlling insect populations, and providing potential sources of medicinal compounds. Highlighting the importance of spider species, the present study was aimed at exploring the diversity of spider fauna and species richness in various habitats in District Mardan, Khyber Pakhtunkhwa, Pakistan, from March 2021 to December 2021. Spiders were collected through different methods: pitfall traps, cryptic searching, ground hand collection, aerial hand collection, and vegetation beating. Then, the captured spiders were washed in alcohol and preserved in a combination of 80% alcohol and 20% glycerol for further observation. Identification was carried out with the help of available spider identification keys and literature. A total of 578 specimens representing 29 species from 17 families and 26 genera were collected and identified. Family Lycosidae was the most dominant family (13.49%), followed by Salticidae (10.2%), Araneidae (8.47%), Tetragnathidae (7.61%), Pholicidae (6.4%), Oxyopidae (5.88%), Thomisidae (5.7%), Clubionidae (5.53%), Sicariidae (5.19%), Scytodidae (5.01%), Corinnidae (4.67%), Agelenidae (4.32%), Cheiracanthiidae and Sparassidae (4.15%), Oecobiidae and Hersiliidae (3.97%) and Theridiidae was the rarest among all (1.21%). The most commonly identified species are Hippasa partita, Lycosa poonaesis, Lycosa terrestris, Draposa oakleyi, Plexippus paykulli, Menemerus nigli, Thyene imperialis, Thyene bivittate and Hasarius adansoni. Argiope versicolor, Neoscona theisi, Tetragnatha extensa, Crossopriza lyoni, and Oxyopes Javanus. During the present study, it was observed that spider species were abundantly found in warm areas from May to August, which demonstrates that the spider fauna of the study area is very rich but has yet to be explored.

Identification of insect body fragments found in fecal samples of Sapajus nigritus (Primates: Cebidae) from five Conservation Units in Rio de Janeiro state, Brazil.

Sapajus nigritus (Primates: Cebidae) is endemic of the Atlantic Forest, occurring from the Southeastern and Southern regions of Brazil to Northeastern Argentina. This species plays a role in two ecosystem services: seed dispersal through endozoochory and insect population control in agricultural plantations and forest environments. Fruits and invertebrates represent approximately 90% of their diet, and there is a large number of insects in the diet of S. nigritus in urban and conserved areas. However, it is known that insect diversity decreases in anthropized environments. Our objective was to identify the insects present in the fecal samples of S. nigritus from five Conservation Units in Rio de Janeiro state, Brazil. We aim to estimate the percentage of each taxon of insects found in feces either, hypothesizing that there are a greater variety of insect species in the diet of S. nigritus that inhabit preserved forested areas. A fecal screening was conducted using a light microscopy and the insects were identified based on their external morphology. Insect fragments were found in eight out of ten fecal samples of S. nigritus, revealing that they belonged to insects from five orders: Hymenoptera, Hemiptera, Orthoptera, Coleoptera and Blattodea, suggesting a good conservation status of the sampling areas.

Insights into sublethal effects of Metarhizium anisopliae on the biotic potentials of Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) on maize

BackgroundEntomopathogenic fungi are an important biological agent in integrated pest management, playing a critical role in controlling insect populations. In the present study, the sublethal effects of the entomopathogenic fungus, Metarhizium anisopliae (Ascomycota: Hypocreales), were investigated on the biotic potential of Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), which is a major pest of economically important crops.ResultsObtained results revealed that exposure to LC50 concentration of M. anisopliae resulted in a significantly longer larval developmental time (3.25–6.45 days) than the control group (2.42–5.49 days). Similarly, pupal duration was longer in the LC50 treatment (8.24 days) than in the control (6.91 days). Adult longevity was also significantly reduced in the LC50 (9.64 days) and LC30 (10.49 days) treatments compared to the control group (11.7 days). The number of eggs laid by female S. frugiperda exposed to LC50 value of M. anisopliae during the immature stages was significantly lower (464.79 eggs) than that in the control groups (696.93 eggs). Furthermore, all population and age-stage-specific parameters were significantly affected by the sublethal exposure to M. anisopliae at LC30 and LC50 values.ConclusionThese results suggest that sublethal exposure to M. anisopliae negatively impacts the life table parameters of S. frugiperda. However, the use of M. anisopliae at sublethal levels may have potential benefits for integrated pest management strategies seeking to reduce the use of chemicals.

Winged Wonders and Lush Landscapes: Exploring the Harmony between Birds and Forests

Birds are essential bio- or eco-engineers that play a vital role in regulating nature, and their interactions with other environmental aspects can be complex and varied. Forests and birds are intricately intertwined. Through their mutual interaction, they create a harmonious living system that supports both parties. Forest birds play a crucial role in maintaining the balance of nature by dispersing seeds, pollinating flowers, and controlling insect populations. In addition to housing and food, forests offer bird's places to nest, wintering grounds, and thermal refuges. The diversity and distribution of forest birds are critical indicators of forest health and ecosystem function. However, factors such as climate change, habitat loss and fragmentation, and human activities profoundly impact the distribution and abundance of forest birds. Addressing these issues and taking action to mitigate their effects is essential. The forest ecosystem and its avian inhabitants can be protected by restoring degraded habitats, putting conservation practices into place, and promoting sustainable forestry practices.

Microplastics pollution in larvae of toads, frogs and newts in anthropopressure gradient

Amphibians are vital components of global biodiversity and fulfil diverse ecological roles, including insect population control and serving as environmental health indicators. However, there is a concerning decline in amphibian populations globally due to factors such as habitat loss, climate change, and emerging diseases. Concurrently, the issue of microplastic pollution has gained prominence because of its potential to harm aquatic ecosystems. Microplastics, derived from various sources, endanger aquatic organisms, especially amphibians during their sensitive larval stages. In this study, we examined the prevalence of microplastic pollution in the larval stages of 10 amphibian species, covering both tailed (Urodela) and tailless (Anura) amphibians. We observed a significant correlation between amphibian species identity, the extent of artificial land cover, and the degree of microplastic contamination in larvae. Notably, our results indicate interspecific differences in microplastic bioaccumulation. Furthermore, this research is the first to demonstrate a positive correlation between microplastic pollution in amphibian larvae and anthropogenic pressure. Our findings add to the expanding literature underscoring the intricate interplay between human activities and aquatic ecosystem health.

Bat activity is related to habitat structure and time since prescribed fire in managed pine barrens in New England.

Several insectivorous bat species are found in New England, yet research on them is still scarce. Current research shows the ecological importance of bats due to their control of insect populations, but they are endangered by habitat loss and White Nose Syndrome, among other threats. Pine barrens are an uncommon ecosystem found in New England that supports other rare taxa and could be important for these bat species. With hand-held audio recorders, we surveyed for bats in Montague Plains Wildlife Management Area in Massachusetts and Concord Pine Barrens in New Hampshire in June 2022. Our study objectives were to (1) describe the most common bat species and (2) compare bat activity across different habitat types at two managed pine barrens in New England. In particular, we examined bat activity related to habitat type (scrub oak, mature pitch pine, treated pitch pine, hardwood forest), habitat structure (i.e., canopy closure), time since prescribed fire, and path width. We analyzed our data through generalized linear modeling and logistic regression. Overall, we were able to measure the presence of five out of the nine total species found in the area, including the endangered Myotis lucifugus (little brown bat). We recorded 293 bat calls, with the majority of calls from big brown bats (71%). We found significant differences (p<0.05) in bat activity in relation to time since prescribed fire and habitat structure. The index of bat activity was greatest in pitch pine and hardwood forests and lowest in scrub oak and treated pitch pine habitats. With preliminary data, we also found that silver-haired bat presence was influenced by habitat type, with more detections at survey points in hardwood forests. These findings demonstrate the importance of pine barrens as an ecosystem that supports bats in New England. According to the activity of bats in our study, closed canopy and mature pitch pine habitats may be prioritized in conservation efforts at managed barrens for bat species. Further research is recommended to better understand the relationship between prescribed fires, which are common in managed barrens, and bat activity.

A Limiting Factor of Sex Attractants of Bactrocera dorsalis (Diptera: Tephritidae), Verified under Laboratory Conditions.

At present, sexual attractants mainly control insect populations by killing males. However, the effect of sex attractants may be limited by the mating ability of the attracted insects. The Oriental fruit fly, Bactrocera dorsalis (Hendel), has a strong reproductive capacity; it brings great losses to agricultural production, which can be controlled by methods using sex attractant methyl eugenol that mainly attracts males. Therefore, we studied the multiple and continuous (as well as consecutive) mating ability of B. dorsalis through behavioral experiments. The results show that male B. dorsalis can mate 11 times on average, with females mating only 1.93 times, and that 10.81% of males mate more than 20 times. The reproductive capacity of male B. dorsalis decreased significantly after four to five instances of continuous mating. In different mating patterns, the reproductive fitness of polyandry is not the highest, rather, interval mating is the best. A limiting factor of the sex attractant effect was revealed in B. dorsalis through behavioral evidence.

Isolation and Identification of Entomopathogenic Fungi from Soils of Manipur (N-E India)

Background: Entomopathogenic fungi (EPF) are natural adversaries of insects, serving a crucial role in the regulation of insect pest populations. In response to the growing demand for sustainable agricultural practices that prioritize environmental protection, human safety and animal welfare, the utilization of bio-control agents like entomopathogenic fungi offers a superior and safe alternative to chemical pesticides. Entomopathogenic fungi effectively infect and eliminate insects, thereby contributing to the control of insect populations through the induction of lethal infections known as epizootics. Isolating EPF from the soil is an effective method as they naturally inhabit soil ecosystems. The north-eastern region of India possesses a forest cover exceeding 80%, with Manipur alone accounting for nearly 75% of forest cover in its total geographical area. This abundant forest cover, along with undisturbed land, contributes to the region’s wealth of micro flora and fauna, including a thriving population of entomopathogenic fungi. However, the potential of these fungi in pest population management remains largely unexplored. Therefore, this study was conducted to investigate the diversity of these promising entomopathogenic fungi. Methods: In this study, we isolated fungi from the soils of ten districts of Manipur and identified several isolates with entomopathogenic properties. Soil bating using Galleria mellonella larvae was employed for the isolation of entomopathogenic fungi. Result: A total of 73 fungal isolates were obtained from 100 soil samples, out of which 54 were identified as entomopathogenic fungi. The genus Aspergillus constituted the most commonly isolated entomopathogenic fungi, followed by isolates of Beauveria, Clonostachys, Talaromyces, Trichoderma, Fusarium, Aspergillus, Candida and Meyerozyma genera. Diversity studies revealed variations in the types and proportions of fungi among different regions of Manipur. Pathogenicity tests confirmed the virulence of the isolated entomopathogenic fungi, with 14 isolates of Beauveria bassiana and two isolates of Talaromyces purpureogenus causing 100% mortality of the test insects. The isolated fungi exhibited excellent performance in insect control and could be further mass-produced for effective pest management.

Bird composition as an environmental quality indicator in Wallacea’s urban area

North Sulawesi Province, part of Wallace Bioregion, has a complex ecosystem. Advanced urban development brings various impacts, such as environmental change. Birds’ existence around human provides some advantages, such as assisting the process of plant pollination, controlling insect populations, and indicators of environmental quality. This study aimed to determine the bird species composition in four locations and the environmental quality was analysed using the Bird Community Index (BCI). This study gathered data on bird species in Manado Bay, Gunung Tumpa, Kawanua Arboretum, and the Kaki Dian areas. We conducted field observation through point count method as primary data and the secondary data were obtained from previous publications. Data were analyzed using Bird Community and Sorenson indexes. This study revealed that the birds’ quantities and composition moderately varied in four locations. This study found 37 bird species in Manado Bay, 33 in Tumpa Mountain, 36 in Kawanua Arboretum, and 49 in the Klabat mountain areas. The Bird Community Index (BCI) accumulation ranged from 56.0 – 68.4 and it was categorized as medium environmental quality. Sorensen’s community similarity index displayed a value of 30.3-51.0% which classified as low to medium community similarity.

A narrow host-range and lack of persistence in two non-target insect species of a bacterial symbiont exploited to deliver insecticidal RNAi in Western Flower Thrips.

Insecticidal RNAi is a targeted pest insect population control measure. The specificity of insecticidal RNAi can theoretically be enhanced by using symbiotic bacteria with a narrow host range to deliver RNAi, an approach termed symbiont-mediated RNAi (SMR), a technology we have previously demonstrated in the globally-invasive pest species Western Flower Thrips (WFT). Here we examine distribution of the two predominant bacterial symbionts of WFT, BFo1 and BFo2, among genome-sequenced insects. Moreover, we have challenged two non-target insect species with both bacterial species, namely the pollinating European bumblebee, Bombus terrestris, and an insect predator of WFT, the pirate bug Orius laevigatus. Our data indicate a very limited distribution of either symbiont among insects other than WFT. Moreover, whereas BFo1 could establish itself in both bees and pirate bugs, albeit with no significant effects on insect fitness, BFo2 was unable to persist in either species. In terms of biosafety, these data, together with its more specific growth requirements, vindicate the choice of BFo2 for delivery of RNAi and precision pest management of WFT.

Effect of marker-free transgenic Chlamydomonas on the control of Aedes mosquito population and on plankton

BackgroundMore than half of the world’s population suffers from epidemic diseases that are spread by mosquitoes. The primary strategy used to stop the spread of mosquito-borne diseases is vector control. Interference RNA (RNAi) is a powerful tool for controlling insect populations and may be less susceptible to insect resistance than other strategies. However, public concerns have been raised because of the transfer of antibiotic resistance marker genes to environmental microorganisms after integration into the recipient genome, thus allowing the pathogen to acquire resistance. Therefore, in the present study, we modified the 3-hydroxykynurenine transaminase (3hkt) and hormone receptor 3 (hr3) RNAi vectors to remove antibiotic resistance marker genes and retain the expression cassette of the inverse repeat sequence of the 3hkt/hr3 target gene. This recombinant microalgal marker-free RNAi insecticide was subsequently added to the suburban water in a simulated-field trial to test its ability to control mosquito population.MethodsThe expression cassette of the 3hkt/hr3 inverted repeat sequence and a DNA fragment of the argininosuccinate lyase gene without the ampicillin resistance gene were obtained using restriction enzyme digestion and recovery. After the cotransformation of Chlamydomonas, the recombinant algae was then employed to feed Aedes albopictus larvae. Ten and 300 larvae were used in small- and large-scale laboratory Ae.albopictus feeding trials, respectively. Simulated field trials were conducted using Meishe River water that was complemented with recombinant Chlamydomonas. Moreover, the impact of recombinant microalgae on phytoplankton and zooplankton in the released water was explored via high-throughput sequencing.ResultsThe marker-free RNAi-recombinant Chlamydomonas effectively silenced the 3hkt/hr3 target gene, resulting in the inhibition of Ae. albopictus development and also in the high rate of Ae. albopictus larvae mortality in the laboratory and simulated field trials. In addition, the results confirmed that the effect of recombinant Chlamydomonas on plankton in the released water was similar to that of the nontransgenic Chlamydomonas, which could reduce the abundance and species of plankton.ConclusionsThe marker-free RNAi-recombinant Chlamydomonas are highly lethal to the Ae. albopictus mosquito, and their effect on plankton in released water is similar to that of the nontransgenic algal strains, which reduces the abundance and species of plankton. Thus, marker-free recombinant Chlamydomonas can be used for mosquito biorational control and mosquito-borne disease prevention.Graphical

Lepidopteran pheromones as potential tools for pest insect control in the Arecaceae family

Lepidoptera is the second larger order of Insecta Class. Lepidopteran which feed of species of the Arecaceae family are notorious for the damage they cause, attacking a range from seedlings to the fruit. There are several control methods used against these pest insets, and among them, chemical pesticides are the most explored. Biological and mechanical control are also relevant, but they require a large number of trained workers. Behaviour modulation through chemical communication, using pheromones, stands out with a great potential to sustainably control insect populations. Pheromones have already been identified in lepidopteran pest which infest Arecaceae plants, they are mainly female-produced compounds, and belong to the sexual and contact types. The majority of pheromone compounds identified to this date are classified as Types I and II (unsaturated C10–C18 alcohols and their derivatives; and unsaturated C17–C25 hydrocarbons and their epoxides, respectively) with rare occurrences of Types 0 (short-chain secondary alcohols) and 3 (methyl-branched structures). Considering the vast quantity of lepidopteran species that attack this family and the economic impacts they generate, the present work aggregates the current knowledge on pheromones used the Integrated Pest Management of lepidopteran insects that damage palm plant species, and discusses both the compounds already applied in the field and the promising one that must yet to be tested.