The low-lethal concentrations of rotenone and pyrethrins suppress the population growth of Rhopalosiphum padi.

As an important pest on winter wheat, Rhopalosiphum padi (L.) causes damage to the wheat yield by sucking plant nutrients, transmitting plant viruses and producing mildew. R. padi has been reported to develop resistance to pyrethroids and neonicotinoids. To explore potential alternative approaches for R. padi control, the activity of 10 botanical insecticides was evaluated. Results suggested that the toxicity of rotenone and pyrethrins to R. padi were the highest and near to the commonly used chemical insecticides. When exposed to the low-lethal concentrations (LC10, LC30) of rotenone or pyrethrins for 24 h, the lifespan and fecundity of adults in F0 generation decreased significantly compared to control. The negative effect could also be observed in the F1 generation, including the decreased average offspring, longevity of adult, and prolonged nymph period. The population parameters in F1 generation of R. padi were also inhibited by exposing to the low-lethal concentrations of rotenone or pyrethrins, including the decreased net reproductive rate, intrinsic rate of natural increase, finite rate of population increase, and gross reproduction rate. Co-toxocity factor results showed that mixtures of rotenone and thiamethoxam, pyrethrins and thiamethoxam showed synergistic effect. Our work suggested that rotenone and pyrethrins showed negative effect on the population growth under low-lethal concentrations. They are suitable for R. padi control as foliar spraying without causing population resurgence.

High-temperature responses of Myzus persicae and its parasitoid Aphidius gifuensis in relation to heat level, duration and developmental stage.

BACKGROUND: Understanding how parasitoids respond to temperature is crucial for improving biological control strategies under the context of global warming. This study examined the suitability of Myzus persicae and its parasitoid Aphidius gifuensis to varying temperature conditions, as well as the stage-specific response of A. gifuensis to high temperatures. RESULTS: High temperatures had a significant impact on the both M. persicae and A. gifuensis. When exposed to 36°C, M. persicae developed more slowly and produced smaller adults compared to control, regardless of the duration of exposure (2, 4 or 6 h); additionally, the survival rate of M. persicae nymphs sharply decreased under these conditions. Exposure to 36°C for 4 h negatively impacted the development of A. gifuensis. Female parasitoids exposed to 32°C developed into smaller adults, whereas males exposed to all three temperature levels were smaller compared to control group. Female parasitoids exposed to high temperatures, regardless of the specific heat level and duration, exhibited reduced longevity and decreased fecundity. None of the parasitoids exposed to 36°C for 6 h daily developed into adults. Heat treated during early developmental stages (2 and 4 days old) had a greater influence on parasitoid development, whereas heat treatment at 4 and 6 days old had a more significant impact on its fecundity. CONCLUSION: High temperatures not only directly affected the performance of A. gifuensis, but also exerted indirect effects by influencing the quality of the host aphids M. persicae. The deleterious effects of high temperature on larvae can persist into the adult stage, affecting the longevity and reproduction of adults. These findings are important for the utilization of A. gifuensis in the control of M. persicae in warming environments. © 2024 Society of Chemical Industry.

Effects of pyriproxyfen on development and hormone of the aphis, Aphis craccivora (Hemiptera: Aphididae).

Pyriproxyfen (PPF) has been shown to affect the pupal stage and ecdysone levels in holometabolous insects, such as silkworms and mealworms. It remains unknown whether it affects hemimetabolous insects with their hormone levels in insects lacking a pupal stage. In this laboratory study, bioassays were conducted to investigate the effects of varying doses of PPF on Aphis craccivora Koch (Hemiptera: Aphididae). Ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was used to determine the types and titers of juvenile hormone (JH) and 20-hydroxyecdysone (20E). Additionally, the effects of PPF on A. craccivora reproduction and molting, as well as its influence on relevant gene expression, were examined. The results revealed LC50 and LC90 values of 3.84 and 7.49 mg/l for PPF, respectively, after 48 h of exposure. The results demonstrated a significant reduction in the titer of JH III and a significant increase in the titer of 20E following treatment with PPF. However, there was no significant decrease observed in the titer of JH III skipped bisepoxide (JH SB3). A sublethal concentration of PPF was found to inhibit Krüppel homolog 1 (kr-h1) gene expression and reduce aphid reproduction, but it did not significantly impact ecdysone receptor expression and aphid molting. The results of this study demonstrate that PPF exhibits a lethal effect on aphids, thereby providing an effective means of control. Additionally, sublethal concentrations of PPF have been found to inhibit the JH in aphids, resulting in a decline in their reproductive ability and achieving the desired control objectives.

DNA methylation machinery is involved in development and reproduction in the viviparous pea aphid (Acyrthosiphon pisum).

Epigenetic mechanisms, such as DNA methylation, have been proposed to mediate plastic responses in insects. The pea aphid (Acyrthosiphon pisum), like the majority of extant aphids, displays cyclical parthenogenesis - the ability of mothers to switch the reproductive mode of their offspring from reproducing parthenogenetically to sexually in response to environmental cues. The pea aphid genome encodes two paralogs of the de novo DNA methyltransferase gene, dnmt3a and dnmt3x. Here we show, using phylogenetic analysis, that this gene duplication event occurred at least 150 million years ago, likely after the divergence of the lineage leading to the Aphidomorpha (phylloxerans, adelgids and true aphids) from that leading to the scale insects (Coccomorpha) and that the two paralogs are maintained in the genomes of all aphids examined. We also show that the mRNA of both dnmt3 paralogs is maternally expressed in the viviparous aphid ovary. During development both paralogs are expressed in the germ cells of embryos beginning at stage 5 and persisting throughout development. Treatment with 5-azactyidine, a chemical that generally inhibits the DNA methylation machinery, leads to defects of oocytes and early-stage embryos and causes a proportion of later stage embryos to be born dead or die soon after birth. These phenotypes suggest a role for DNA methyltransferases in reproduction, consistent with that seen in other insects. Taking the vast evolutionary history of the dnmt3 paralogs, and the localisation of their mRNAs in the ovary, we suggest there is a role for dnmt3a and/or dnmt3x in early development, and a role for DNA methylation machinery in reproduction and development of the viviparous pea aphid.

Design, Synthesis, and Bioactivity of Trifluoroethylthio-Substituted Phenylpyrazole Derivatives.

As the first marketed phenylpyrazole insecticide, fipronil exhibited remarkable broad-spectrum insecticidal activity. However, it poses a significant threat to aquatic organisms and bees due to its high toxicity. Herein, 35 phenylpyrazole derivatives containing a trifluoroethylthio group on the 4 position of the pyrazole ring were designed and synthesized. The predicted physicochemical properties of all of the compounds were within a reasonable range. The biological assay results revealed that compound 7 showed 69.7% lethality against Aedes albopictus (A. albopictus) at the concentration of 0.125 mg/L. Compounds 7, 7g, 8d, and 10j showed superior insecticidal activity for the control of Plutella xylostella (P. xylostella). Notably, compound 7 showed similar insecticidal activity against Aphis craccivora (A. craccivora) compared with fipronil. Potential surface calculation and molecular docking suggested that different lipophilicity and binding models to the Musca domestica (M. domestica) gamma-aminobutyric acid receptors may be responsible for the decreased activity of the tested derivatives. Toxicity tests indicated that compound 8d (LC50 = 14.28 mg/L) induced obviously 14-fold lower toxicity than fipronil (LC50 = 1.05 mg/L) on embryonic-juvenile zebrafish development.

Seasonal population fluctuation and life history in different temperatures of Myzus cerasi (Hemiptera: Aphididae) on cherry trees: a field and laboratory study.

This study determined the seasonal population fluctuation of Myzus cerasi (Fabricius) (Hemiptera: Aphididae) in cherry orchards and the effect of different temperatures on the life-history parameters of these aphids under laboratory conditions. Our field results showed that the population fluctuations and densities of M. cerasi on cherry trees were positively affected by the temperature increase between seasons. Also, our laboratory results showed that M. cerasi survived and reproduced at all temperatures tested under laboratory conditions. Female longevity was observed as 19.00 ±â€…2.38, 18.72 ±â€…0.49, and 12.59 ±â€…0.74 days, and fecundity was 10.14 ±â€…2.26, 9.36 ±â€…0.59, and 7.27 ±â€…0.84 offspring/female at 20, 25, and 30 °C, respectively. Although the highest net reproductive rate (R0) was observed numerically at 25 °C (7.80 offspring/female), there was no significant difference compared to 20 °C (7.10 offspring/female). The highest intrinsic rate of increase (r) and the highest finite rate of increase (λ) were calculated at 30 °C (0.15 ±â€…0.01 and 1.16 ±â€…0.01 day-1, respectively), and there was no significant difference compared to 25 °C. The mean generation time (T) of M. cerasi showed a significant difference at all temperatures tested and decreased from 22.59 ±â€…0.33 days at 20 °C to 12.78 ±â€…0.37 days at 30 °C. Consequently, our results revealed that the seasonal population fluctuation and the life history of M. cerasi in the field and laboratory conditions were affected significantly by different temperatures. Our data obtained in the field and the laboratory will contribute to the understanding of M. cerasi biology and to the management of the pest.

Hormetic effect induced by Beauveria bassiana in Myzus persicae.

BACKGROUND: Myzus persicae, a serious sap-sucking pest of a large variety of host plants in agriculture, is traditionally controlled using chemical insecticides but there is interest in using biopesticides as restrictions are increasingly placed on the use of broad-spectrum pesticides. RESULTS: Here, we show that in Petri dish experiments, high concentrations of the fungal entomopathogen Beauveria bassiana led to rapid mortality of M. persicae, although at a low concentration (1 × 104 conidia mL-1) there is a hormetic effect in which survival and fecundity are enhanced. Hormetic effects persisted across a generation with reduced development time and increased fecundity in the offspring of M. persicae exposed to B. bassiana. The whole-plant experiment points to a hormetic effect being detected in two out of three tested lines. The impact of these effects might also depend on whether M. persicae was transinfected with the endosymbiont Rickettsiella viridis, which decreases fecundity and survival compared with aphids lacking this endosymbiont. This fecundity cost was ameliorated in the generation following exposure to the entomopathogen. CONCLUSION: Although B. bassiana is effective in controlling M. persicae especially at higher spore concentrations, utilization of this entomopathogen requires careful consideration of hormetic effects at lower spore concentrations, and further research to optimize its application for sustainable agriculture is recommended. © 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Effect of the mycotoxins enniatin B and deoxynivalenol on the wheat aphid Sitobion avenae and on the predatory lacewing Chrysoperla carnea.

BACKGROUND: Fusarium species are responsible for Fusarium head blight (FHB) in wheat, resulting in yield losses and mycotoxin contamination. Deoxynivalenol (DON) and enniatins (ENNs) are common mycotoxins produced by Fusarium, affecting plant, animal and human health. Although DON's effects have been widely studied, limited research has explored the impact of ENNs on insects. This study examines the influence of DON and enniatin B (ENB), both singularly and in combination, on the wheat aphid Sitobion avenae and one of its predators, the lacewing Chrysoperla carnea. RESULTS: When exposed to DON (100 mg L-1) or DON + ENB (100 mg L-1), S. avenae exhibited significantly increased mortality compared to the negative control. ENB (100 mg L-1) had no significant effect on aphid mortality. DON-treated aphids showed increasing mortality from 48 to 96 h. A dose-response relationship with DON revealed significant cumulative mortality starting at 25 mg L-1. By contrast, C. carnea larvae exposed to mycotoxins via cuticular application did not show significant differences in mortality when mycotoxins were dissolved in water but exhibited increased mortality with acetone-solubilized DON + ENB (100 mg L-1). Feeding C. carnea with aphids exposed to mycotoxins (indirect exposure) did not impact their survival or predatory activity. Additionally, the impact of mycotoxins on C. carnea was observed only with acetone-solubilized DON + ENB. CONCLUSIONS: These findings shed light on the complex interactions involving mycotoxins, aphids and their predators, offering valuable insights for integrated pest management strategies. Further research should explore broader ecological consequences of mycotoxin contamination in agroecosystems. © 2024 Society of Chemical Industry.

RpUGT344J7 is involved in the reproduction switch of Rhopalosiphum padi with holocyclic life cycle.

Many aphid species exhibit both cyclical parthenogenesis (CP) and the obligate parthenogenesis (OP) life history, which are genetically determined. In CP aphid lineages, the parthenogenetic individuals can switch from asexual to sexual reproduction quickly in response to environmental factors such as changes in photoperiod and temperature. However, the OP aphid lineages do not undergo sexual reproduction under any conditions. So far, mechanisms underlying the reproduction switch in CP aphids have not been fully elucidated. Rhopalosiphum padi, a serious worldwide insect pest of wheat, has both CP and OP lineages. Uridine diphosphate-glycosyltransferases (UGTs) are enzymes that participate in the metabolic detoxification of xenobiotics. Here, we identified 43 RpUGT genes from R. padi genome and transcriptome sequences, and found that: (1) the UGT content of the CP lineage was significantly higher than that in the OP lineage at the key time points when CP lineage mainly produce virginoparae, gynoparae, and males under inducing condition, while there were no significant difference under normal conditions; (2) RpUGT344J7 gene was highly expressed during the time points when CP lineages produce gynopara and males; (3) the critical time points for CP lineages to produce virginoparaee, gynoparae, and males were affected when the CP lineages were injected with dsRpUGT344J7; (4) the knockdown of RpUGT344J7 caused a significant reduction in the total number of virginoparae, gynoparae, and males in the offspring under inducing condition. The findings contribute to our understanding of the molecular mechanisms underlying the quick shift from asexual to sexual reproduction in aphid species.

Canola bee pollen is an effective artificial diet additive for improving larval development of predatory coccinellids: a lesson from Harmonia axyridis.

BACKGROUND: Pollen is a common plant-derived food source for predatory ladybird beetles under field conditions, yet the potential for pollen to improve the quality of artificial diets remains largely unexplored. In this study, we developed three pollen diets by incorporating varying proportions of canola bee pollen (7.5%, 15.0% and 22.5% with 2.5%, 5.0%, and 7.5% of water, respectively) into a conventional diet. The feeding efficiency of Harmonia axyridis, an omnivorous predator, was evaluated and compared on three pollen diets, a conventional nonpollen diet and pea aphids. RESULTS: The larvae fed a medium or high pollen diet exhibited significantly higher survival in the 4th instar, pupa and adult stages than those fed a nonpollen diet. These larvae also developed into significantly heavier adults, and their survival rates in adulthood were comparable to those fed pea aphids. Specifically, we revealed the underlying mechanisms through which a high pollen diet enhances pupal development. Consumption of high pollen diet versus nonpollen diet resulted not only in a significant decrease in pupal glycogen content, but also an increase in adult lipid content. Both diet treatments induced similar changes in carbohydrate and glycogen content compared to the aphid diet while exhibiting different alterations in pupal protein content and adult lipid content. Furthermore, the transcriptome analysis revealed that the nutrient metabolism, immune response, and cuticle development pathways were predominantly enriched among the differentially expressed genes (DEGs). CONCLUSION: Canola bee pollen offers diverse advantages in terms of rearing H. axyridis larvae with an artificial diet, which will advance the development of effective diets for predaceous coccinellids. © 2024 Society of Chemical Industry.

Evolutionary diversification of insulin-related peptides (IRPs) in aphids and spatiotemporal distribution in Acyrthosiphon pisum.

Members of the insulin superfamily activate the evolutionarily highly conserved insulin/insulin-like growth factor signaling pathway, involved in regulation of growth, energy homeostasis, and longevity. In the current study we focus on aphids to gain more insight into the evolution of the IRPs and how they may contribute to regulation of the insulin-signaling pathway. Using the latest annotation of the pea aphid (Acyrthosiphon pisum) genome, and combining sequence alignments and phylogenetic analyses, we identified seven putative IRP encoding-genes, with IRP1-IRP4 resembling the classical insulin and insulin-like protein structures, and IRP5 and IRP6 bearing insulin-like growth factor (IGF) features. We also identified IRP11 as a new and structurally divergent IRP present in at least eight aphid genomes. Globally the ten aphid genomes analyzed in this work contain four to 15 IRPs, while only three IRPs were found in the genome of the grape phylloxera, a hemipteran insect representing an earlier evolutionary branch of the aphid group. Expression analyses revealed spatial and temporal variation in the expression patterns of the different A. pisum IRPs. IRP1 and IRP4 are expressed throughout all developmental stages and morphs in neuroendocrine cells of the brain, while IRP5 and IRP6 are expressed in the fat body. IRP2 is expressed in specific cells of the gut in aphids in non-crowded conditions and in the head of aphids under crowded conditions, IRP3 in salivary glands, and both IRP2 and IRP3 in the male morph. IRP11 expression is enriched in the carcass. This complex spatiotemporal expression pattern suggests functional diversification of the IRPs.

Thermal development of the endoparasitoid Aphelinus maculatus Yasnosh (Hymenoptera: Aphelinidae) parasitizing Myzus persicae Sulzer (Homoptera: Aphididae).

The aphid parasitoid, Aphelinus maculatus Yasnosh, was first documented in China in 2016. It is important to make clear of the effects of temperatures on the development of this aphid parasitoid for the future using as a aphid biological control agent. So the thermal requirements, lower developmental threshold (t), thermal constant (K), upper developmental threshold (Tm) and optimum developmental temperature (To) for the egg-mummy, mummy-adult and egg-adult periods of A. maculatus were established under the laboratory conditions. The studies were conducted at five constant temperatures (13, 18, 23, 28, and 33 °C) and with a 16 L: 8D photoperiod. Lower developmental threshold (t) and thermal constant (K) were estimated by fitting linear model. Upper developmental threshold (Tm) and optimal developmental temperature (To) were estimated by fitting Logan I non-linear model. The results turned out that the lower (t) and the upper developmental thresholds (Tm) for egg-adult period were 5.59 °C and 28.17 °C, respectively. The thermal constants (K) for egg-mummy, mummy-adult, and egg-adult periods were estimated at 121.51, 127.88, and 243.90 degree-days, respectively. The optimal developmental temperature (To) for egg-adult period was 27.45 °C calculated by the model, but the survival rate was only 40.68% at the temperature of 28 °C. The highest survival rate was 74.32% at temperature of 23 °C, implying that A. maculatus preferentially developed at the temperate regions of temperature.

Aphids and Ants, Mutualistic Species, Share a Mariner Element with an Unusual Location on Aphid Chromosomes.

Aphids (Hemiptera, Aphididae) are small phytophagous insects. The aim of this study was to determine if the mariner elements found in the ant genomes are also present in Aphis fabae and Aphis hederae genomes and the possible existence of horizontal transfer events. Aphids maintain a relationship of mutualism with the ants. The close contact between these insects could favour horizontal transfer events of transposable elements. Myrmar mariner element isolated from Myrmica ruginodis and Tapinoma ibericum ants have also been found in the two Aphis species: A. fabae and A. hederae (Afabmar-Mr and Ahedmar-Mr elements). Besides, Afabmar-Mr could be an active transposon. Myrmar-like elements are also present in other insect species as well as in one Crustacean species. The phylogenetic study carried out with all Myrmar-like elements suggests the existence of horizontal transfer. Most aphids have 2n = 8 with a XX-X0 sex determination system. Their complicated life cycle is mostly parthenogenetic with sexual individuals only in autumn. The production of X0 males, originated by XX females which produce only spermatozoa with one X chromosome, must necessarily occur through specialized cytogenetic and molecular mechanisms which are not entirely known. In both aphid species, the mariner elements are located on all chromosomes, including the X chromosomes. However, on the two X chromosomes, no positive signals are detected in their small DAPI-negative telomere regions. The rDNA sites are located, as in the majority of Aphids species, on one of the telomere regions of each X chromosome. The hybridization patterns obtained by double FISH demonstrate that Afabmar-Mr and Ahedmar-Mr elements do not hybridize at the rDNA sites of their host species. Possible causes for the absence of these transposons in the rDNA genes are discussed, probably related with the X chromosome biology.

Case Study Using Recommended Reference Genes Actin and 18S for Reverse-Transcription Quantitative Real-Time PCR Analysis in Myzus persicae.

Myzus persicae is a globally important pest with the ability to adjust to a wide range of environmental situations, and many molecular technologies have been developed and applied to understand the biology and/or control this pest insect directly. Reverse-transcription quantitative real-time PCR (RT-qPCR) is a primary molecular technology that is used to quantify gene expression. Choosing a stable reference gene is significantly important for precisely clarifying the expression level of the target gene. Actin and 18S have been recommended as stable compounds for real-time RT-qPCR in M. persicae under the tested biotic and abiotic conditions. In this study, we checked the stability of Actin and 18S by analyzing the relative expression levels of the cytochrome 450 monooxygenase family member genes CYP6CY3 and CYP6-1, carboxylesterase gene E4 and vacuolar protein sorting gene VPS11 via RT-qPCR under various conditions. The expression levels of these four target genes were normalized using both Actin and 18S individually and the combination of these two genes. Our results confirmed that Actin and 18S can be used as reference genes to normalize the expression of target genes under insecticide treatment and starvation in M. persicae. However, at the developmental stages of M. persicae, the expression of the four tested target genes was normalized stably by Actin but not 18S, with the latter presenting a problematic change with the developmental stages. Thus, the stability of reference genes in response to diverse biotic and abiotic factors should be evaluated before each RT-qPCR experiment.

Multi-generational Effects of Different Resistant Wheat Varieties on Fitness of Sitobion avenae (Hemiptera: Aphididae).

Crop resistance plays a role in preventing aphid damage, benefiting food production industries, but its effects are limited due to aphid adaptation and phenotypic plasticity. Therefore, furthering understanding of aphid-crop interactions will improve our ability to protect crops from aphids. To determine how aphids adapt to resistant varieties of wheat, Triticum aestivum L. over time, we performed a laboratory experiment to assess the multi-generational effects of three wheat varieties, Batis, Ww2730, and Xiaoyan22, with different resistance levels on the fitness of Sitobion avenae (Fab.) (Hemiptera: Aphididae). The results showed that Ww2730 and Xiaoyan22 were more resistant than Batis to S. avenae, regardless of whether the aphids were newly introduced or had been acclimated before being introduced to the three wheat varieties. However, the effect of resistance on aphid life-history traits was time dependent. Aphid weigh gain increased and they development faster of the acclimated generation compared to the newly introduced generation on all three varieties. And the fecundity on the three varieties and net reproduction rates on Batis and Xiaoyan22 significantly decreased. Aphid fitness in terms of individual life-history parameters improved, whereas aphid fitness in terms of reproductive decreased, and a convergence effect, the difference gaps and standard errors of all life-history traits among the three acclimated populations had narrowed and were less than those in the three first-generation populations, was observed during the 3-mo experimental period. We suggested that S. avenae could rapidly respond to wheat resistance through life-history plasticity.

Genome-wide analysis of long non-coding RNAs and their association with wing development in Aphis citricidus (Hemiptera: Aphididae).

Long non-coding RNAs (lncRNAs) play critical roles in the various physiological processes of insects. The wing is a successful adaptation allowing insects to escape from unfavorable environments, while information on lncRNAs related to wing development is limited. In this study, we constructed 12 libraries from two RNA-seq comparisons: 4th instar winged nymphs versus winged adults and 4th instar wingless nymphs versus wingless adults in the brown citrus aphid Aphis citricidus, to identify the wing development-associated lncRNAs. A total of 2914 lncRNAs were identified and 50 lncRNAs were differentially expressed during the 4th instar winged nymphs to winged adults transition, and 28 lncRNAs changed during the 4th instar wingless nymphs to wingless adults transition. The differentially expressed lncRNAs were grouped into six clusters according to the expression patterns in the combined two-winged morphs. lncRNA Ac_lnc54106.1 was up-regulated during 4th instar winged nymphs to winged adults transition, but a lack of change during the 4th instar wingless nymphs to wingless adults transition implied a critical role in the specific regulation of wing development. RNA interference of Ac_lnc54106.1 resulted in malformed wings. Targets prediction, expression patterns, and RNAi assay results showed that Ac_lnc54106.1 may target the PiggyBac transposable element-derived protein 4 (PGBD4) gene, decrease expression of the canonical wing development-related genes, and finally regulate wing development. The systematic identification of lncRNAs in an aphid increases our understanding of how non-coding RNA mediates the wing plasticity of insects.

Effects of imidacloprid and thiamethoxam on the development and reproduction of the soybean aphid Aphis glycines.

The soybean aphid Aphis glycines Matsumura (Hemiptera: Aphididae) is a primary pest of soybeans and poses a serious threat to soybean production. Our studies were conducted to understand the effects of different concentrations of insecticides (imidacloprid and thiamethoxam) on A. glycines and provided critical information for its effective management. Here, we found that the mean generation time and adult and total pre-nymphiposition periods of the LC50 imidacloprid- and thiamethoxam-treatment groups were significantly longer than those of the control group, although the adult pre-nymphiposition period in LC30 imidacloprid and thiamethoxam treatment groups was significantly shorter than that of the control group. Additionally, the mean fecundity per female adult, net reproductive rate, intrinsic rate of increase, and finite rate of increase of the LC30 imidacloprid-treatment group were significantly lower than those of the control group and higher than those of the LC50 imidacloprid-treatment group (P < 0.05). Moreover, both insecticides exerted stress effects on A. glycines, and specimens treated with the two insecticides at the LC50 showed a significant decrease in their growth rates relative to those treated with the insecticides at LC30. These results provide a reference for exploring the effects of imidacloprid and thiamethoxam on A. glycines population dynamics in the field and offer insight to agricultural producers on the potential of low-lethal concentrations of insecticides to stimulate insect reproduction during insecticide application.

Identification and Behavioral Assays of Alarm Pheromone in the Vetch Aphid Megoura viciae.

Aphids are destructive pests, and alarm pheromones play a key role in their chemical ecology. Here, we conducted a detailed analysis of terpenoids in the vetch aphid, Megoura viciae, and its host plant Pisum sativum using gas chromatography/mass spectrometry. Four major components, (-)-ß-pinene (49.74%), (E)-ß-farnesene (32.64%), (-)-α-pinene (9.42%) and ( +)-limonene (5.24%), along with trace amounts of ( +)-sabinene, camphene and α-terpineol) (3.14%) were found in the aphid. In contrast, few terpenoids were found in the host plant, consisting mainly of squalene (66.13%) and its analog 2,3-epoxysqualene (31.59%). Quantitative analysis of the four major terpenes in different developmental stages of the aphid showed that amounts of the monoterpenes increased with increasing stage, while the sesquiterpene amount peaked in the 3rd instar. (-)-ß-Pinene was the most abundant terpene at all developmental stages. Behavioral assays using a three-compartment olfactometer revealed that the repellency of single compounds varied in a concentration-dependent manner, but two mixtures [(-)-α-pinene: (-)-ß-pinene: (E)-ß-farnesene: ( +)-limonene = 1:44.4:6.5:2.2 or 1:18.4:1.3:0.8], were repellent at all concentrations tested. Our results suggest that (-)-α-pinene and (-)-ß-pinene are the major active components of the alarm pheromone of M. viciae, but that mixtures play a key role in the alarm response. Our study contributes to the understanding of the chemical ecology of aphids and may help design new control strategies against this aphid pest.

Identifying aphid resistance in the ancestral wheat Triticum monococcum under field conditions.

Wheat is an economically, socially, and nutritionally important crop, however, aphid infestation can often reduce wheat yield through feeding and virus transmission. Through field phenotyping, we investigated aphid resistance in ancestral wheat Triticum monococcum (L.). Aphid (Rhopalosiphum padi (L.), Sitobion avenae (F.) and Metopolophium dirhodum (Wlk.)) populations and natural enemy presence (parasitised mummified aphids, ladybird adults and larvae and lacewing eggs and larvae) on two naturally susceptible wheat varieties, Triticum aestivum (L.) var. Solstice and T. monococcum MDR037, and three potentially resistant genotypes T. monococcum MDR657, MDR045 and MDR049 were monitored across three years of field trials. Triticum monococcum MDR045 and MDR049 had smaller aphid populations, whereas MDR657 showed no resistance. Overall, natural enemy presence was positively correlated with aphid populations; however, MDR049 had similar natural enemy presence to MDR037 which is susceptible to aphid infestation. It is hypothesised that alongside reducing aphid population growth, MDR049 also confers indirect resistance by attracting natural enemies. The observed resistance to aphids in MDR045 and MDR049 has strong potential for introgression into commercial wheat varieties, which could have an important role in Integrated Pest Management strategies to reduce aphid populations and virus transmission.

Mutualistic interaction of aphids and ants in pepper, Capsicum annuum and Capsicum frutenscens (Solanaceae) / Interacción mutualista de pulgones y hormigas en pimiento, Capsicum annuum y Capsicum frutenscens (Solanaceae)

Abstract Introduction: Adequate biological identification is fundamental for establishing integrated pest management programs and identifying the trophic and mutualist relationships that can affect pest population dynamics. Aphids are the main pest of pepper Capsicum spp. (Solanaceae) crops in Southwestern Colombia, due to their role as vectors of viruses. However, the identification of aphid species is complex, limiting the investigations performed to address their interactions with other organisms. Ants and aphids present a facultative mutualistic relationship, that promotes the growth of hemipteran colonies, for this reason, the study of the ecological mutualistic association between aphids and ants is important. Objective: The main objective was to discriminate the aphid species present in commercial crops of Capsicum spp., and to identify the ant community that attends the aphid colonies and its effects on the size of the aphid colonies. Methods: Aphid species, and their ant mutualist, were collected from Capsicum annuum and Capsicum frutescens, in the Cauca valley, Southwestern Colombia. We used the DNA barcoding approach to identify aphid species, and the ants were identified by morphology-based taxonomy. To evaluate the effect of ant care on the size and structure of aphid colonies, generalized linear models were calculated using as the response variables the total number of aphids for each colony and the proportion of nymphs. Results: The aphid species that attack pepper crops, are: Aphis gossypii and Myzus persicae (Hemiptera: Aphididae), with A. gossypii being the species that interacts with ants (19 ant species). A. gossypii colonies attended by ants had larger sizes and more nymphs per colony, than those not attended. Conclusions: Although the aphid-ant interaction is not species-specific, it is necessary to consider its role in the propagation of viral diseases in peppers and to determine how this interaction may affect regional biological control strategies.

Resumen Introducción: La adecuada identificación biológica es fundamental para establecer programas de manejo integrado de plagas e identificar las relaciones tróficas y mutualistas que pueden afectar la dinámica poblacional de insectos plaga. Los áfidos son las principales plagas del ají Capsicum spp. (Solanaceae) en el suroccidente colombiano, debido a su rol como vectores de virus. Sin embargo, su identificación es compleja, y limita las investigaciones que intentan revelar sus interacciones con otros organismos. Las hormigas y los áfidos presentan una relación mutualista facultativa, que promueve el crecimiento de las colonias de los hemípteros, por esta razón, el estudio de la asociación ecológica y mutualista entre áfidos y hormigas es importante. Objetivo: El principal objetivo de esta investigación fue discriminar las especies de áfidos presentes en cultivos comerciales de Capsicum spp., e identificar la comunidad de hormigas que atiende las colonias de áfidos y su efecto en el tamaño de las colonias de áfidos. Métodos: Los áfidos, y las hormigas mutualistas de estos áfidos, se recolectaron de Capsicum annuum y Capsicum frutescens, en el valle del rio Cauca, en el suroccidente colombiano. Se empleó el Código de barras del ADN para identificar las especies de áfidos, y las hormigas se identificaron empleando taxonomía basada en morfología. Para evaluar el efecto que tiene el cuidado de las hormigas sobre el tamaño de las colonias de áfidos, se empleó un modelo lineal generalizado, utilizando como variables de respuesta el número total de áfidos por cada colonia y la proporción de ninfas por colonia. Resultados: Las especies de áfidos que atacan los cultivos de ají, son: Aphis gossypii y Myzus persicae (Hemiptera: Aphididae), siendo A. gossypii la especie que interactúa con hormigas (19 especies). Las colonias de A. gossypii atendidas por hormigas presentan mayor tamaño y número de ninfas, que aquellas desatendidas. Conclusiones: Aunque la interacción áfido-hormiga no es especie específica, es necesario considerar su rol en la propagación de enfermedades virales en plantas cultivadas y determinar cómo esta interacción puede afectar la implementación de estrategias de control biológico.