Efficiency Of Biological Control Research Articles

Ambulatory dispersal of Typhlodromus (Anthoseius) recki Wainstein (Acari: Phytoseiidae) along Solanceae stem.

Tomato crops are attacked by several pests, including mites. While the main predatory mites are not effective enough to control mite pests, recent studies have shown encouraging results with the European endemic phytoseiid Typhlodromus (Anthoseius) recki. The first objective of the study was to assess the ability of this species to disperse along the tomato stem, considering six genotypes of Solanum lycopersicum, S. peruvianum and S. cheesmaniae with contrasted trichome numbers and types of stem trichomes, accuratetly characterised in a previous study. The second objective was to determine how predator morphological traits can explain dispersal along the tomato stem. For this, ambulatory dispersal ability of females (stem crossing rate success, hesitation and escape behavior, mobility periods) was tested in lab conditions on the eight Solanum genotypes, at four period of time after the predator introduction (10, 25, 55 and 100min), with a video observation of 5min at each period. The females were then mounted on slides and body length and width (at the fore hind, middle and back parts) measured. No effect of the tomato genotypes was observed on the dispersal ability of the predator. However, specimens that succeeded in crossing the stem, had a higher percentage of mobility time (79.36%) than those that failed (43.60%). Furthermore, body width at midbody (DSW2) and dorsal shield length (DSL) were negatively correlated with dispersal ability. The mean DSL and DSW2 of the females that succeed to cross were 342.3 and 160.9μm, respectively vs. 345.6 and 164.9μm, for females that did not succeed. This suggests that the more slender and relatively small the specimens, the more are mobile and able to successfully cross the stem. The number of glandular trichomes type (GT) VI and to a lesser extent GT I and IV, and non-glandular trichomes (NGT) II&III appear to limit dispersal. The GT VI seems to have a repellent effect. On the opposite, the number of NGT V were positively correlated with high mobility and stem crossing rates. Assuming that the main barrier to biological control efficiency is dispersal along tomato stems, these preliminary results should have implications for biological control success. The proportion of mites with 'optimal dimensions' appears to be low and further studies should be undertaken to better assess the proportion of mites with such ideal dimensions in different populations and also to determine whether these morphological traits are associated with different feeding abilities and/or abiotic conditions.

Toxicological assessment of cadmium exposure through Hyphantria cunea larvae on the predation fitness of Arma chinensis

Heavy metals are defined as an abiotic factor that affects the efficiency of biological pest control. This study constructed a cadmium (Cd)-polluted artificial diets–Hyphantria cunea–Arma chinensis food chain to analyze the effects of Cd exposure on the ability of A. chinensis to control H. cunea. The results revealed that Cd was transferred through the artificial diet to H. cunea larvae and A. chinensis nymphs via a biological amplification effect. After feeding on Cd-accumulated H. cunea larvae, the body weight of A. chinensis nymphs reduced, mortality increased, developmental duration prolonged, and the expression of growth regulatory genes (EX, cycE, and MER) decreased. Cd activated the antioxidant defense system of the nymphs, accompanied by a significant enhancement in the contents of H2O2 and MDA, marked damage to the midgut sub-microstructure, and a remarkable induction in the expression of genes crucial for the mitochondrial pathway/ER stress–apoptosis pathway. Cd significantly diminished the contents of total amino acids, glucose, free fatty acids, and expression of the genes (HK2, PFK, IDH1, and IDH2) essential for the TCA cycle and glycolysis in the nymphs. The preference of the A. chinensis nymphs to Cd-treated H. cunea larvae was evidently reduced. Cd diminished the search-ability, food intake, instantaneous attack rate, and maximum theoretical daily food intake but prolonged the feeding time of the nymphs. Taken together, Cd exposure reduces the ability of A. chinensis nymphs to control H. cunea and provides a new challenge for the efficiency of insect pest control using natural enemies. These findings have important reference value for optimizing pest control strategies in heavy metal polluted areas.

Development of Bacillus thuringiensis-based liquid and paste formulations for controlling invasive pest species Spodoptera frugiperda J. E. Smith

Spodoptera frugiperda J.E. Smith (Spodoptera: Noctuidae) is an invasive pests of maize that has been reported around the world. Control efforts using biological agents continue to be developed, including the use of entomopathogen bacteria such as Bacillus thuringiensis. To boost the efficacy and efficiency of biological control, formulations are required. The objective of this study was to develop biopesticide formulations and evaluate their efficacy. The research was carried out by formulating B. thuringiensis strain BtJ2 (1010 cfu mL -1) in liquid and paste formulations. The effectiveness of the formulations was evaluated using the feed dipping method. The results showed that paste formulations at a concentration of 10% caused 100% mortality, whereas the liquid formulation resulted in 85% mortality. The LC90 for the paste formulation was 6.66%, while the LC90 for the liquid formulation was 12.90%. Both the liquid and paste formulations had similar effects on mortality and viability. Based on the LC90 and LT90, the paste formulation was more efficient and faster in killing S. frugiperda than the liquid formulation. The results of this study provide recommendations that B. thuringiensis as a bioinsecticide is better formulated in a paste than in a liquid form.

Compatibility of Trichoderma harzianum with commercial herbicides

Biological disease control has become popular in recent years and has established itself as a viable alternative to chemical control. However, the efficiency of biological control can be limited by the application technology. Thus, the objective of this work was to evaluate the compatibility of Trichoderma harzianum with three commercial herbicides. The fungus was incubated in culture medium supplemented with doses of three commercial herbicides and incubated for 4 days. The CI50 (concentration capable of inhibiting 50% of the mycelial growth of the fungus) was determined for each herbicide and compared with the recommended doses for field application. All herbicides tested reduced mycelial growth, with CI50 lower than the recommended doses. The data suggest low compatibility between T. harzianum and the tested herbicides.

Water stress decreases the biocontrol efficacy of a nucleopolyhedrovirus against the fall armyworm on maize

AbstractDrought events are expected to limit crop productivity in the context of current climate change. Drought is also likely to affect multitrophic interactions such as those involving plants, phytophagous insects and their natural enemies. We designed a two-phase experiment to test the effect of water availability and fertilizer treatment on the interaction between maize, the fall armyworm and its nucleopolyhedrovirus pathogen. Plants grown in soil with high irrigation and mineral fertilization had the highest shoot and root dry weight. Furthermore, plant nitrogen levels were higher in plants with fertilization and a low irrigation scheme compared to other treatments. Low irrigation of maize plants reduced virus-induced mortality of armyworm larvae. Insects did not feed on plants with high irrigation and without fertilization. We conclude that water stress and plant nutrition can affect virus performance and thereby affect the efficiency of biological control and pest management, especially as water and nutrient limitation will likely increase under climate change.

Evolution of knockdown resistance (kdr) mutations of Aedes aegypti and Aedes albopictus in Hainan Island and Leizhou Peninsula, China.

Aedes aegypti and Aedes albopictus are important vectors of human arboviruses, transmitting arboviral diseases such as yellow fever, dengue, chikungunya and Zika. These two mosquitoes coexist on Hainan Island and the Leizhou Peninsula in China. Over the past 40 years, the distribution of Ae. albopictus has gradually expanded in these areas, while the distribution of Ae. aegypti has declined dramatically mainly due to the ecological changes and some other factors such as heavy use of insecticide indoor based on endophagic bloodfeeding of the species. This study focused on the knockdown resistance (kdr) genes of both mosquitoes, investigated their mutations, and analyzed their haplotype and evolutionary diversity combined with population genetic features based on the ND4/ND5 genes to further elucidate the molecular mechanisms underlying the development of insecticide resistance in both mosquitoes. Three mutations, S989P, V1016G and F1534C, were found to be present in Ae. aegypti populations, and the three mutations occurred synergistically. Multiple mutation types (F1534C/S/L/W) of the F1534 locus are found in Ae. albopictus populations, with the three common mutations F1534C, F1534S and F1534L all having multiple independent origins. The F1534W (TTC/TGG) mutation is thought to have evolved from the F1534L (TTC/TTG) mutation. The F1534S (TTC/TCG) mutation has evolved from the F1534S (TTC/TCC) mutation. The most common form of mutation at the F1534 locus found in this study was S1534C, accounting for 20.97%, which may have evolved from the F1534C mutation. In addition, a new non-synonymous mutation M1524I and 28 synonymous mutations were identified in Ae. albopictus populations. Correlation analysis showed that the genetic diversity of Ae. aegypti and Ae. albopictus populations did not correlate with their kdr haplotype diversity (P>0.05), but strong gene flow between populations may have contributed to the evolution of the kdr gene. The study of kdr gene evolution in the two mosquito species may help to identify the evolutionary trend of insecticide resistance at an early stage and provide a theoretical basis for improving the efficiency of biological vector control and subsequent research into new insecticides.

Screening and Analysis of Antifungal Strains Bacillus subtilis JF-4 and B. amylum JF-5 for the Biological Control of Fusarium Wilt of Banana.

This study aimed to identify the antagonistic bacteria from the rhizosphere of healthy bananas that can effectively suppress the Fusarium wilt of banana, and to further investigate the inhibitory mechanism. The primary and secondary screening techniques were implemented using the double-plate and fermentation antagonism methods. The strain was identified based on physiological and biochemical tests, 16S rRNA gene sequencing, and specific gene amplification. The effects of crude extract on the protein content, lipid peroxidation, and pectinase activity of mycelia were determined from the identified isolates. Two antagonistic bacteria, JF-4 and JF-5, were screened and initially identified as Bacillus subtilis (GenBank: OR125631) and B. amylum (GenBank: OR125632). The greenhouse experiment showed that the biological control efficiency of the two antagonists against the Fusarium wilt of banana was 48.3% and 40.3%, respectively. The catalase content produced by lipid peroxidation increased significantly after treatment with the crude extracts of JF-4 and JF-5 at concentrations of 0.69 μmol/L and 0.59 μmol/L, respectively. The protein and ergosterol content and pectinase activity decreased significantly. The two antagonistic bacteria might inhibit the growth of pathogens by enhancing lipid peroxidation and decreasing the synthesis of cell metabolites. Twenty compounds were identified by gas chromatography-mass spectrometry (GC-MS). B. subtilis JF-4 was further sequenced and assembled to obtain a complete circular chromosome genome of 681,804,824 bp. The genome consisted of a 4,310,825-bp-long scaffold. The findings of this study may help elucidate the mechanism behind this biocontrol isolate.

Double-strand RNAs targeting MaltRelish and MaltSpz reveals potential targets for pest management of Monochamus alternatus

Overcoming the innate immunity of insects is a key process to improve the efficiency of biological control. Antimicrobial peptides (AMPs) are important effectors in insect innate immunity, usually mediating resistance to pathogenic microorganisms through Toll and IMD signaling pathways. This study investigated the effect of key genes on upstream immune recognition receptor (GNBP3) and downstream effectors (AMPs) by RNAi technology. The transcriptome KEGG enrichment analysis and differential gene annotation results showed that the immune response genes MaltSpz and MaltRelish are important regulators of Toll and IMD signaling pathways, respectively. Both dsSpz and dsRelish could affect AMP gene expression and increase the expression of the immune recognition receptor MaltGNBP3. Moreover, they significantly reduce the survival rate of Monochamus alternatus and promote hyphal growth after Beauveria bassiana infection. This helps to improve the biological control effect of B. bassiana, control the population of vector insects and cut off the transmission route of pine wood nematode. The combined MaltSpz and MaltRelish knockdown increased the infection rate of M. alternatus larvae from 20.69% to 83.93%, achieving the best efficiency in synergistic B. bassiana infection. Our results showed important roles of MaltRelish- and MaltSpz-mediated regulation of AMP genes function in insect entomopathogenic fungi tolerance and induced significant mortality in larvae. Based on this study, MaltSpz and MaltRelish could represent candidate gene targets for the biological control of M. alternatus by RNAi.

Identification and Expression Profiling of the 5-HT Receptor Gene in Harmonia axyridis.

It has been found that 5-hydroxytryptamine (5-HT) modulates the feeding of some insects, and this phenomenon was found in Harmonia axyridis (Pallas) by our previous study. An understanding of the 5-HT system in this beetle is helpful for utilizing 5-HT to modulate its predation to improve biological control efficiency, especially in greenhouses in winter in north China. This is because 5-HT influences diapause in insects by modulating the synthesis and release of prothoracic hormone (PTTH) and, therefore, influences feeding. To elucidate the molecular basis of the H. axyridis 5-HT system, reverse-transcription polymerase chain reaction (RT-PCR), multiple sequence alignment, and phylogenetic tree construction were used to identify the 5-HT receptor in H. axyridis, and quantitative real-time PCR (qRT-PCR) was used to analyze the expression pattern of these receptor genes in different developmental stages and in the nervous system (brain + ventral nerve cord), digestive tract, pectoral muscles, and gonads of the adult ladybird. The results showed that four 5-HT receptors were identified in H. axyridis, named 5-HT1AHar, 5-HT1BHar, 5-HT2Har, and 5-HT7Har. The four receptors were expressed at high levels in the adult stage, especially in 2-day-old adults, with expression levels of 18.72-fold (male) and 14.21-fold (female) of that in eggs for 5-HT1A, 32.27-fold (male) and 83.58-fold (female) of that in eggs for 5-HT1B, 36.82-fold (male) and 119.35-fold (female) of that in eggs for 5-HT2, and 165.47-fold (male) and 115.59-fold (female) of that in eggs for 5-HT7. The level of expression decreased with the advance of day-age in adults. The levels of expression of 5-HT1BHar, 5-HT2Har, and 5-HT7Har were low at the egg, larval, and pupal stages, and 5-HT1AHar was not expressed in the larval stage. The four receptors were expressed in the nervous system, digestive tract, pectoral muscles, and male and female gonads. The 5-HT1AHar was expressed at a high level in the pectoral muscle (6.75-fold of that in the nervous system), 5-HT1BHar in male gonads (1.02-fold of that in the nervous system) and the nervous system, 5-HT2Har in male gonads (5.74-fold of that in the nervous system), and 5-HT7Har in the digestive tract (1.81-fold of that in the nervous system). The results of this study will lay a foundation for research on the function of the 5-HT receptor by RNA interference in the regulation of predation by H. axyridis.

Activation of MAPK signaling pathway genes leads to promoted thermotolerance in a high-temperature adapted predatory mite Neoseiulus barkeri (Hughes)

Predatory mites are important biological control agents for phytophagous mites and several small insect pests on vegetables, while the control efficiency is often limited by the changeable or fluctuating environment, especially under the threat of global warming. To mitigate the undesired impacts of high temperature environment, a high-temperature adapted strain (HTAS) of the predatory mite Neoseiulus barkeri (Hughes) was screened from a conventional strain (CS) by long-term heat acclimation (35°C) and regular heat hardenings (45°C). In this study, to investigate the molecular mechanisms of enhanced thermotolerance in HTAS N. barkeri, four mitogen-activated protein kinase (MAPK) pathway genes were identified from the predatory mite N. barkeri. The expression levels at different developmental stages showed four MAPK pathway genes were highest at adults and lowest at eggs or nymphs in both strains. Under 42℃ high temperature stress, the expression levels of four identified MAPK pathway genes increased rapidly at a short time in both N. barkeri strains and the magnitude of expression increase in HTAS N. barkeri was even more evident. In addition, the MAPK pathway genes expression in CS N. barkeri sharply decreased following longer exposure periods at 4 h, whereas the expression in HTAS N. barkeri remained elevated after 4 h. These results suggested that MAPK signaling pathway participated in the formation of thermotolerance in predatory phytoseiid mites, which provided new insights in promoting the biological control efficiency of predatory mites under changeable environment.

Bacillus velezensis BER1 enriched Flavobacterium daejeonense-like bacterium in the rhizosphere of tomato against bacterial wilt.

Beneficial microorganisms can protect crop from phytopathogens, and modify rhizosphere microbiome. However, it is not well-understood whether or how do rhizosphere microorganisms which respond to bioagents contribute to disease suppression. Bacillus velezensis BER1 and tomato bacterial wilt caused by Ralstonia solanacearum were selected as models to disentangle the interactions and mechanisms in the rhizosphere. Bacillus velezensis BER1 greatly suppressed tomato bacterial wilt by over 49.0%, reduced R. solanacearum colonization in the rhizosphere by 36.3%, and significantly enriched two Flavobacterium ASVs (1357 and 2401). A novel colony loop-mediated isothermal amplification (LAMP) assay system was developed to screen out Flavobacterium from tomato rhizosphere bacterial isolates. In vitro tests revealed that cocultivating BER1 with Flavobacterium C45 increased biofilm formation by 18.6%. Climate chamber experiment further revealed that Flavobacterium C45 improved the control efficiency of BER1 on tomato bacterial wilt by 46.0%, decreased the colonization of R. solanacearum in the rhizosphere by 43.1% and elevated the transcription of plant defense gene PR1α in tomato by 45.4%. In summary, Flavobacterium C45 boosted the ability of B. velezensis BER1 to prevent bacterial wilt and the colonization of R. solanacearum, highlighting the importance of helper bacteria on elevating the efficiency of biological control.

Cadmium (Cd) exposure through Hyphantria cunea pupae reduces the parasitic fitness of Chouioia cunea: A potential risk to its biocontrol efficiency

Heavy metal contamination has been regarded as an environmental variable that affects the efficiency of pest biological control, but the parasitic fitness of parasitoids under heavy metal stress is poorly understood. Herein, the effect of Cd exposure through the host pupa of Hyphantria cunea on the parasitic fitness of Chouioia cunea was investigated, and the mechanism by which Cd exposure affects the interaction between H. cunea and C. cunea from the perspective of innate immunity in host insect and the oxidative status in the parasitoid offspring was explored. Our results indicated that Cd can be transferred from the H. cunea pupae to the parasitoid offspring, and the transfer coefficient reflected biological amplification. There were no significant differences in the rates of parasitism success and offspring emergence between the untreated and Cd-treated groups. However, after parasitizing Cd-accumulated pupae, the parasitic fitness of offspring wasps (e.g., the number, individual size and life span) decreased significantly. Under Cd exposure, the cellular and humoral immunity of H. cunea pupae decreased significantly. Compared with the untreated group, the H2O2 content of parasitoid offspring in the Cd-treated group was significantly increased. Cd exposure significantly inhibited superoxide dismutase activity in parasitoid offspring, but the contents of ascorbic acid and glutathione were significantly increased by Cd stress. Taken together, these results indicate that Cd exposure reduces the cyclic utilization efficiency of C. cunea on H. cunea pupae. The oxidative status of parasitoid offspring triggered by Cd exposure could be responsible for the reduced parasitic fitness of C. cunea on Cd-accumulated H. cunea pupae.

Valuation The efficiency of Nanotechnology and biological activity of Nanoparticle for two plant extracts Ricinus communis and Neriun oleander against immature stages of Greater wax moth.Galleria mellonella (Lepidoptera: pyralidae)

The results of present study conducted on the Laboratory of advance entomology \ Department of biology \ Faculty of Education for Girls \ University of Kufa, during the years 2018-2019 for evaluating The efficiency of Nanotechnology and biological control and the effect of two plant extracts on the different immature stages of the greater wax moth Galleria mellonella (Lepidoptera: Pyrallidae). eggs, first and fourth larval instars. The cold aqueous extract of castor Ricinus communis and Nerium oleander leaves ,from which different concentrations ( 1,2,3 and 4) mg \ ml were prepared in the Laboratory. The experiments include the enhancement of these plant extracts of toxic nature with chemically prepared particles, silver nanoparticles, and conducting multiple experiments for the same instars of the insect, which was treated with aqueous plant extracts .The statistical results as well as the observation during different stages of the experiments were superior of these nanoextracts over plant extracts in the mortality of eggs and first and fourth latval instars. Experiments indicated that the mortality percentages when treated with aqueous leaves extract of castor were (76, 91, 96) % respectively while the same instars were treated with nano extract of castor was(83.3 ,92.3 ,98.6 )% respectivly . The leaves extract of N.oleander was (86.6%, 96.6%, 99.4%) compared with (93.3, 100, 100) % respectively of the nanoparticle of the eggs and larvae of the first and fourth phases at 4 mg / ml. It also proved that the first instar was the most sensitive to the extract of the fourth instar, where the highest mortality percentages was (96.6, 100) % compared with (86.6, 93.3)% respectively of the first and fourth larval instars when treated with and nano of N. oleander and R.communis respectively.

Cadmium contamination triggers negative bottom-up effects on the growth and reproduction of Frankliniella occidentalis (Thysanoptera: Thripidae) without disrupting the foraging behavior of its predator, Orius sauteri (Heteroptera: Anthocoridae).

Heavy metal contaminants may influence tri-trophic interactions among plants, herbivores, and their natural enemies and affect the results of pest management practices. We examined how the widely distributed heavy metal cadmium (Cd) could modify interactions between kidney bean, Phaseolus vulgaris L., western flower thrips, Frankliniella occidentalis Pergande, and a predator, Orius sauteri (Poppius) by examining Cd effects on the feeding damage on leaves, the growth and reproduction of the thrips, and the feeding and plant location selection behaviors of predators. Leaf feeding damage was significantly reduced only at the highest Cd treatment (625mg L-1). Survival, reproduction, and population growth of thrips decreased with the increase of Cd treatment concentration (0, 25, and 625mg L-1). The reproduction rate of thrips from the highest Cd treatment group was reduced to less than 30% of the controls. Predator choice of plants was not impacted at the lowest level of Cd treatment (25mg L-1) when prey were excluded, but the predators were deterred from plants treated at the high level of Cd (625mg L-1). However, the predators responded strongly to the presence of prey, and the Cd-based deterrence was effectively eliminated when prey were added. Thus, the presence of Cd can cause a bottom-up effect on the fitness of pests without disrupting the foraging behavior of its predator. Our results provide baseline data on the toxic impacts on the pest and predator, and indicate that the ecology of the system and the biological control efficiency would be potentially impacted by high levels of Cd (625mg L-1).

Linking life table and predation rate for evaluating temperature effects on Orius strigicollis for the biological control of Frankliniella occidentalis

IntroductionOrius spp. are generalist predators released in horticultural and agricultural systems to control thrips. Understanding the effects of temperature on the development, predation rate, and population dynamics of Orius is essential for identifying the optimal timing of Orius release for establishing an adequate population to facilitate synchrony with thrips population growth and to prevent thrips outbreaks. The biological control efficiency of natural enemies as well as predator–prey relationships can be precisely described by integrating life table parameters and the predation rate.MethodsIn this study, the demographic features of Orius strigicollis fed on 2nd instar nymphs of western flower thrips (WFT), Frankliniella occidentalis, were compared at 18.5, 23.5, 27, and 33°C using the TWOSEX-MSChart program. The CONSUME-MSChart program was used to examine predation rates under different temperatures (18.5, 23.5, and 27°C).ResultsThe results showed no significant difference in fecundity among those reared at 18.5, 23.5, and 27°C, but fecundity at these temperatures was significantly higher than that at 33°C. The intrinsic rate of increase (r), finite rate of increase (λ), and net reproduction rate (R0) were the highest at 27°C. The net predation rate (C0) and transformation rate (Qp) were significantly higher at 18.5°C (C0 = 168.39 prey/predator, Qp = 8.22) and 23.5°C (C0 = 140.49 prey/predator, Qp = 6.03) than at 27°C (C0 = 138.39 prey/predator, Qp= 3.81); however, the finite predation rate (ω) showed the opposite trend. In addition to temperature, the stage of O. strigicollis at release can affect population dynamics.DiscussionOur study showed that temperature influenced the demographic traits and predation rates of O. strigicollis. When planning a release, the stage of O. strigicollis and temperature should be taken into account to establish an adequate population for the control of WFT.

Functional analysis of odorant-binding proteins for the parasitic host location to implicate convergent evolution between the grain aphid and its parasitoid Aphidius gifuensis

(E)-β-farnesene (EBF) is a typical and ecologically important infochemical in tri-trophic level interactions among plant-aphid-natural enemies. However, the molecular mechanisms by which parasitoids recognize and utilize EBF are unclear. In this study, we functionally characterized 8 AgifOBPs in Aphidifus gifuensis, one dominant endo-parasitoid of wheat aphid as well as peach aphid in China. Among which, AgifOBP6 was the only OBP upregulated by various doses of EBF, and it showed a strong binding affinity to EBF in vitro. The lack of homology between AgifOBP6 and EBF-binding proteins from aphids or from other aphid natural enemies supported that this was a convergent evolution among insects from different orders driven by EBF. Molecular docking of AgifOBP6 with EBF revealed key interacting residues and hydrophobic forces as the main forces. AgifOBP6 is widely expressed among various antennal sensilla. Furthermore, two bioassays indicated that trace EBF may promote the biological control efficiency of A. gifuensis, especially on winged aphids. In summary, this study reveals an OBP (AgifOBP6) that may play a leading role in aphid alarm pheromone detection by parasitoids and offers a new perspective on aphid biological control by using EBF. These results will improve our understanding of tri-trophic level interactions among plant-aphid-natural enemies.

Suitable doses screening for mutagenesis in Phytoseiulus persimilis induced by <sup>60</sup>Co-γ

Phytoseiulus persimilis Athias-Henriot (Acari: Phytoseiidae) is a specialist predator of Tetranychus sp.; however, the lack of resistance to high temperatures and drought may result in the lower biological control efficiency of P. persimilis in the adverse climatic conditions. In breeding programs, 60Co-γ irradiation is commonly used to quickly screen suitable mutants, optimize biological characteristics, and improve resistance. It is expected that 60Co-γ irradiation could be useful in resistance screening in P. persimilis. The purpose of this study is to determine the suitable doses of 60Co-γ with high levels of mutagenesis in P. persimilis. P. persimilis individuals were irradiated using 60Co-γ at 0, 20, 40, 60, 70, 75, 80, 85, 90, 95, 100, 200, 300, and 400 Gy, with a dose rate of 0.5 Gy/min. The mortality of irradiated individuals was used to estimate the LD50. The fecundity of survived individuals and egg hatch rate were applied to estimate the mutagenesis frequency. The mortality of P. persimilis increased with increasing irradiation dose with a rapid increase between 70 to 95 Gy. When irradiation dose exceeded 100 Gy, almost all P. persimilis died. The LD50 of irradiation dose was ca. 80 Gy. When irradiation doses increased from 70 to 95 Gy, sterility rate increased from 5% to 20%, fecundity decreased from 97% to 80%, and egg hatch rate decreased from 98% to 60%. We suggest that the appropriate irradiation doses of 60Co-γ inducing higher P. persimilis mutagenesis were between 70 Gy and 95 Gy. Results of this study allow future large-scale screening for resistant strains of P. persimilis.

Intercropping collard plants with coriander modulates behavioral interactions among aphidophagous predators by altering microhabitat structure

Intercrops increase microhabitat structural complexity and may affect the strength of intraguild predation, facilitating the coexistence of species in aphidophagous guilds that share similar resources. Microhabitat structure may also influence the outcome of intraguild predation among larval stages by influencing the selection of oviposition sites. We investigated how intercrops affect intraguild predation, consumption, and behavioral interactions among various life stages of aphidophagous predators. We examined interactions among conspecific and heterospecific pairs of Cycloneda sanguinea (Coleoptera: Coccinellidae) and Chrysoperla externa (Neuroptera: Chrysopidae) in collards planted in monoculture (simple microhabitat) or intercropped with coriander (complex microhabitat). Heterospecific pairs had reduced impact on their shared prey, especially in monocultures. Chrysoperla externa larvae acted as intraguild predators more often than C. sanguinea larvae and changed the foraging behavior of the intraguild prey. Microhabitat complexity in the intercrop did not extend the period of larval coexistence when intraguild predation was strong. Cycloneda sanguinea avoided laying eggs in the presence of C. externa in the monoculture, and tended to lay more eggs in sheltered locations in the intercrop. Conversely, C. externa laid more eggs in the presence of C. sanguinea, especially in the monoculture. Our findings suggest that the increased microhabitat complexity of the intercrop reduced both the encounter rate between intraguild prey and intraguild predator during larval stages, and the overlap in oviposition site selection by adult females. Our findings highlight the relevance of plant diversity and microhabitat architecture in promoting the coexistence of aphidophagous predators throughout their life cycle, and their potential to increase the efficiency of conservation biological control.

The odorant receptor co-receptor gene contributes to mating and host-searching behaviors in parasitoid wasps.

Biological control of pest insects by parasitoid wasps is an effective and environmentally friendly strategy compared with the use of synthetic pesticides. Successful courtship and host-search behaviors of parasitoid wasps are important for biological control efficiency and are often mediated by chemical odorant cues. The odorant receptor co-receptor (Orco) gene has an essential role in the perception of odors in insects. However, the function of Orco in the mating and host-searching behaviors of parasitoid wasps remains underexplored. We identified the full-length Orco genes of four Drosophila parasitoid species in the genus Leptopilina, namely L. heterotoma, L. boulardi, L. syphax and L. drosophilae. Sequence alignment and membrane-topology analysis showed that Leptopilina Orcos had similar amino acid sequences and topology structures. Phylogenetic analysis revealed that Leptopilina Orcos were highly conserved. Furthermore, the results of quantitative real-time polymerase chain reactions showed that all four Orco genes had a typical antennae-biased tissue expression pattern. After knockdown of Orco in these different parasitoid species, we found that Orco-deficient male parasitoid wasps, but not females, lost their courtship ability. Moreover, Orco-deficient female parasitoid wasps presented impaired host-searching performance and decreased oviposition rates. Our study demonstrates that Orcos are essential in the mating and host-searching behaviors of parasitoid wasps. To our knowledge, this is the first time that the functions of Orco genes have been characterized in parasitoid wasps, which broadens our understanding of the chemoreception basis of parasitoid wasps and contributes to developing advanced pest management strategies. © 2022 Society of Chemical Industry.

Biological control needs evolutionary perspectives of ecological interactions

While ecological interactions have been identified as determinant for biological control efficiency, the role of evolution remains largely underestimated in biological control programs. With the restrictions on the use of both pesticides and exotic biological control agents (BCAs), the evolutionary optimization of local BCAs becomes central for improving the efficiency and the resilience of biological control. In particular, we need to better account for the natural processes of evolution to fully understand the interactions of pests and BCAs, including in biocontrol strategies integrating human manipulations of evolution (i.e., artificial selection and genetic engineering). In agroecosystems, the evolution of BCAs traits and performance depends on heritable phenotypic variation, trait genetic architecture, selection strength, stochastic processes, and other selective forces. Humans can manipulate these natural processes to increase the likelihood of evolutionary trait improvement, by artificially increasing heritable phenotypic variation, strengthening selection, controlling stochastic processes, or overpassing evolution through genetic engineering. We highlight these facets by reviewing recent studies addressing the importance of natural processes of evolution and human manipulations of these processes in biological control. We then discuss the interactions between the natural processes of evolution occurring in agroecosystems and affecting the artificially improved BCAs after their release. We emphasize that biological control cannot be summarized by interactions between species pairs because pests and biological control agents are entangled in diverse communities and are exposed to a multitude of deterministic and stochastic selective forces that can change rapidly in direction and intensity. We conclude that the combination of different evolutionary approaches can help optimize BCAs to remain efficient under changing environmental conditions and, ultimately, favor agroecosystem sustainability.