4th Instars Research Articles

Bombyx mori miR-2845 represses the expression of fibroin light chain gene both in vitro and in vivo.

To study the regulatory function of Bombyx mori (B. mori) miRNAs (bmo-miR) on the expression of fibroin light chain gene (BmFib-L), the 3’UTR of BmFib-L mRNA was used as the target for online prediction of miRNAs from miRBase using RNAhybrid Software, and miR-2845 was screened out. First, the expression profiles of miR-2845 and BmFib-L in larvae of the 5th instar were analyzed by Real-time quantitative PCR (RT-qPCR). Then recombinant plasmids (pcDNA3.0-pre-miR-2845 and pGL3.0-BmFib-L) were constructed to use for the expression of miR-2845 and BmFib-L 3’UTR, respectively. Cellular-level functional verification of miR-2845 on BmFib-L was carried out using multiple experimental methods (including dual luciferase reporter vectors, artificially synthesized mimics and inhibitors, and target site mutations). Finally, in vivo functional verification was performed by injecting the recombinant vector in 5th instar larvae. BmFib-L expression levels were detected using RT-qPCR in the posterior silk glands (PSG) of the injected larvae. Results showed that the expression of miR-2845 increased between the 1st and 5th day in 5th instar larvae, but began to decline on the 5th day, while the expression of the target gene BmFib-L increased sharply. This suggests that miR-2845 and BmFib-L expression levels show opposing trends, implying a negative regulatory relationship. In BmN cells, miR-2845 significantly down-regulated the expression of BmFib-L; the inhibitory effect of miR-2845 on BmFib-L was disappeared after mutation of the targeting site on 3’UTR of BmFib-L; in individuals, miR-2845 significantly down-regulated BmFib-L expression levels. Our results provide new experimental data for clarifying the molecular regulation mechanism of silk protein expression.

Compatibility of entomopathogenic nematodes with insecticides against the cabbage white butterfly, Pieris rapae L. (Lepidoptera: Pieridae)

BackgroundCompatibility of entomopathogenic nematodes (EPNs) with insecticides is a crucial mainstay of integrated pest management (IPM) programs. This study was designed to evaluate the joint action of EPN species and insecticides when employed to deter 3rd and 4th larval instars of cabbage white butterfly, Pieris rapae L. (Lepidoptera: Pieridae) under laboratory conditions. EPNs [Steinernema carpocapsae (All strain), S. feltiae (Filipjev), Heterorhabditis bacteriophora (HP88), and H. bacteriophora (Ar-4)], at concentrations of 50, 100, and 125 IJs/larva, were tested with 3 insecticides (lambda-cyhalothrin, emamectin benzoate, and indoxacarb) at LC25 and LC50 values. Additionally, expression profiles of 2 detoxification genes (CYP6AE120 and PrGSTs1) when the 4th instar larvae were treated by H. bacteriophora (HP88) and lambda-cyhalothrin were examined.ResultsData indicated that statistically significant mortality of 2 larval instars of P. rapae was observed in vitro among EPN species and pesticide concentrations. At concentration of 50 IJs/larva, LT50 values were 2.385 and 3.92 days for S. carpocapsae (All strain) and H. bacteriophora(Ar-4), respectively, on 3rd instar larvae; also, these values were 3.506 and 3.107 days for S. feltiae and H. bacteriophora (Ar-4), respectively, on 4th instar larvae Lambda-cyhalothrin was the most toxic insecticide, followed by emamectin benzoate and indoxacarb at LC25 and LC50, respectively. An additive effect was observed between EPN species with LC25 and LC50 of the tested insecticides, except for lambda-cyhalothrin at LC50 with H. bacteriophora (Ar-4), and indoxacarb, with all EPNs showing antagonistic effects on mortality of 3rd instar larvae after 3 days post-treatment. The interaction between the tested pesticides at LC25 and LC50 and EPN species, showed an additive effect, excluding lambda-cyhalothrin at LC25 with S. carpocapsae (All strain) and LC25 of indoxacarb with H. bacteriophora (Ar-4), which showed potentiation effects. The interaction of S. feltiae (Filipjev) with tested insecticides at LC50 exhibited an antagonistic effect on the mortality of 4th instar P. rapae larvae after 3 days post-treatment. The expression of both CYP6AE120 and PrGSTs1 was significantly up-regulated with lambda-cyhalothrin, followed by H. bacteriophora (HP88) compared to control.ConclusionsThe findings suggested that combining EPNs and the pesticide concentrations can be a practical strategy for managing P. rapae and could pave the way to using new control technologies in protecting organic farm vegetables from lepidopteran pests.

A New Tool Against Anopheles Gambiae 4th Instar Larvae; Ocimum basilicum Mediated Silver Nanoparticles

A New Tool Against Anopheles Gambiae 4th Instar Larvae; Ocimum basilicum Mediated Silver Nanoparticles

Termitophily Documented in Earwigs (Dermaptera)

Simple SummaryIn the current report, we describe a new earwig species, Spirolabia kaja Kočárek, sp. nov. found in an association with the wood-boring termite in a dipterocarp rain forest in Borneo. To evaluate the level of association with termites we documented termite–earwig interactions in the laboratory. We found that earwigs and termites mutually communicate by antennation, and we observed no form of aggressive behavior. The earwigs responded to the proximity of an experimentally irritated termite soldier by the feigning of death (thanatosis), which seems to be a defensive reaction. The occurrence of earwig adults together with the nymphs in the galleries termite strongly suggests that the earwig reproduces inside the termite colony. Spirolabia kaja Kočárek, sp. nov. is the first earwig species for which termitophily has been demonstrated.Based on behavioral observations, we report termitophily by the earwig Spirolabia kaja Kočárek, sp. nov. (Spongiphoridae: Labiinae). The new species was found in association with the wood-boring termite Schedorhinotermes sarawakensis (Holmgren, 1913) in a dipterocarp rain forest in Borneo; in addition to being observed in the galleries, termite–earwig interactions were subsequently documented in the laboratory. We found that earwigs and termites communicate by antennation, and we observed no form of targeted mutual or unilateral aggressive behavior. The earwigs responded to the proximity of an experimentally irritated termite soldier by conflict-avoidance behavior based on thanatosis, which seems to be a defensive reaction that may reduce the chance of being attacked by an irritated termite. Based on the analysis of gastrointestinal tract contents, we conclude that S. kaja sp. nov. is an omnivorous species that feeds mainly on plant tissues and fungi but occasionally on arthropod remains. The occurrence of S. kaja sp. nov. adults together with the nymphs (2nd to 4th instars) in the galleries of S. sarawakensis strongly suggests that the earwig can reproduce inside the termite colony. Spirolabia kaja Kočárek, sp. nov. is the first earwig species for which termitophily has been demonstrated.

Efficacy of Thai indigenous entomopathogenic nematodes for controlling fall armyworm (Spodoptera frugiperda)\xa0(J. E. Smith)(Lepidoptera; Noctuidae)

BackgroundUnder laboratory and greenhouse conditions, the virulence of 2 isolates of Thai indigenous entomopathogenic nematodes (EPNs) in controlling the fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith) (Lepidoptera; Noctuidae), was demonstrated. Six EPNs dosages were tested against 2 larval instars of FAW under the laboratory conditions, while 2 different concentrations were tested under the greenhouse conditions.ResultsThe results of a laboratory experiment revealed that 2 Thai indigenous EPNs isolates (Heterorhabditis indica isolate AUT 13.2 and Steinernema siamkayai isolate APL 12.3) were efficient against the FAW, 2nd and 5th larval instars. Six different nematode concentrations (50,100, 150, 200, 250 and 300 infectious juveniles (IJs) ml−1) were evaluated, and all were proven to be effective, with the mortality rate associated with concentration. Inoculated larvae in the 2nd instar was more vulnerable than that in the 5th instar. H. indica isolate AUT 13.2 was more destructive than S. siamkayai isolate APL 12.3. The greatest mortality rate of 2nd instar larvae was 83% when H. indica AUT 13.2 was applied at the concentration of 250 IJs ml−1, and 68% when the nematode S. siamkayai APL 12.3 was used at the concentration of 300 IJs ml−1. At 250 IJsml−1, the highest mortality rate of the 5th instar larvae was 45% for H. indica AUT 13.2 and 33% for S. siamkayai APL 12.3, respectively. To customize the concentration and volume of nematodes suspension evaluated in the greenhouse settings, the most sensitive stage of FAW and the optimum concentration that caused the highest mortality were used. The concentrations of both indigenous nematodes’ isolates were 20,000 and 50,000 IJsml−1 per pot, respectively, and the results showed that the mortality rates were lower than that in the laboratory. FAW mortality rate was the highest (58%) in case of the nematode H. indica isolate AUT 13.2, against (45%) in case of S. siamkayai isolate APL 12.3, at the 50,000 IJs ml−1 concentrations.ConclusionsThe study revealed the 2 Thai indigenous EPNs isolates (H. indica isolate AUT 13.2 and S. siamkayai isolate APL 12.3) were capable of controlling the FAW in both laboratory and greenhouse environments. The 2 Thai EPNs showed the potential to be considered as a biological control agent.

Evaluation of Metarhizium rileyi Farlow (Samson) impregnated with azadirachtin and indoxacarb against Helicoverpa armigera (Hubner)

BackgroundEntomopathogenic fungi are the most versatile having a wide host range, capable of infecting insects at different developmental stages. In the present study, Metarhizium rileyi, at the concentrations of 102, 103, 104, 105, 106, 107 and 108 conidia/ml and sub-lethal concentrations of azadirachtin (1.02 and 1.53 ppm) and indoxacarb (0.72 ppm) were evaluated against the 1st, 2nd, 3rd, 4th and 5th larval instars of Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) under laboratory conditions.ResultsM. rileyi applied at 106 conidia/ml caused a maximum mortality of 83.33 and 80.00% of 1st and 2nd larval instars of H. armigera, respectively. The maximum mortality of 3rd, 4th and 5th larval instars of H. armigera with 108 conidia/ml of M. rileyi was 83.33, 76.67 and 53.33%, respectively. When M. rileyi blended with azadirachtin at 1.02 ppm, the highest mortality rate of 86.21% at 106 conidia/ml against 2nd instar larvae was resulted. Similarly, M. rileyi applied at 108 conidia /ml mixed with azadirachtin (1.53 ppm) showed 89.66% mortality of 3rd instar larvae. The 2nd instar larvae treated with M. rileyi at 106 conidia/ml, mixed with indoxacarb (0.72 ppm), the corrected mortality rate was 82.14%. Concentration mortality response of 3rd instar larvae to M. rileyi blended with indoxacarb (0.72 ppm) was 85.71% at 108 conidia/ml. The median lethal concentration (LC50) values were 5.51 × 103, 1.86 × 104, 2.81 × 105 and 5.55 × 105 conidia/ml for 1st, 2nd, 3rd and 4th larval instars, respectively, after 7 days of treatment. M. rileyi when mixed with sub-lethal concentrations of azadirachtin (1.02 ppm) and indoxacarb (0.72 ppm) resulted LC50 values of 1.09 × 104 conidia/ml and 1.37 × 104 conidia/ml against 2nd instar larvae, respectively, after 24 hours. Similarly, M. rileyi mixed with sub-lethal concentrations of azadirachtin (1.53 ppm) and indoxacarb (0.72 ppm) resulted LC50 values of 3.12 × 108 and 3.06 × 105 conidia/ml against 3rd instar larvae, respectively, after 24 hours. The study revealed that the susceptibility of larvae decreased in case of large larval instars.ConclusionsM. rileyi can be utilized as one of the component of Integrated Pest Management Program for the eco-friendly management of H. armigera. As the application of M. rileyi @ 107 conidia/ml alone or in combination with azadirachtin (1.02 and 1.53 ppm) or indoxacarb (0.72 ppm) resulted to the highest mortality.

Thermal energy requirement for tobacco caterpillar Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae) development on artificial diet


 Development and survival of tobacco caterpillar Spodoptera litura larvae and pupae were studied at each of seven constant temperatures, 15±1, 18±1, 21±1, 24±1, 27±1, 30±1 and 33±1°C, in incubators. Oviposition, in-cubation, larval and pupal periods were recorded at each of the temperatures. The survival from 1st instar to adult emergence ranged between a maximum of 60% at 24°C and 30% at each of 18°C and 33°C. Developmental duration of different larval instars and pupae declined with an increase in temperature from 15 to 33°C. The optimum temperature for larval and pupal survival in S .litura on artificial diet was observed to be 24°C. On the other hand, optimum temperature range for oviposition was observed to be 27-33°C.The relationship between temperature (T) and development rate (r) was established using linear regression to estimate the thermal constant (K) and development threshold (T0).Thermal constant for 1st to 6th larval instars were computed as 76.9, 90.9, 125, 83.3, 62.5, 90.9 and 200 degree days (DD), respectively, with corresponding development thresholds as 12.8, 11.7, 9.8, 10.3, 10, 10.9 and 13.2oC. Single developmental threshold for larval stage was computed as 13°C.These thermal constants and development thresholds can be used in developing mechanistic population simulation model, which in turn will facilitate the assessment of climate change impact on the pest.

Effects of Aqueous Extracts of Endophyte-Infected Grass Achnatherum inebrians on Growth and Development of Pea Aphid Acyrthosiphon pisum.

Simple SummaryDrunken horse grass Achnatherum inebrians is a widely distributed perennial poisonous grass on the grasslands of Northern and Northwestern China. The present study focused on contact toxicity of aqueous extracts of endophyte-infected (E+) and endophyte-free (E−) plants of A. inebrians in different growth periods on pea aphids. These results show that extracts from endophyte-containing plants may contain compounds that may be used to control insects and lay a foundation for deeper chemical analysis to identify insecticidal compounds.The pea aphid Acyrthosiphon pisum has a worldwide distribution and causes serious losses for agricultural production. Drunken horse grass Achnatherum inebrians is a widely distributed perennial poisonous grass on the grasslands of Northern and Northwestern China. The present study focused on contact toxicity activity of aqueous extracts of endophyte-infected (E+) and endophyte-free (E−) A. inebrians in different growth periods of pea aphids, and the growth and development of two color morphs of F1 generation nymphs. Both of the color morphs had development durations in E+ treatments that tended to be longer at 1st, 2nd, 3rd, and 4th instars than E− and control (CK). The E+ treated aphids also showed decreased weights at maturity with over all lower mean relative growth rates (MRGR). Aphid survival of E+ treated aphids was lower than that of E− and CK at all growth periods. Seeding stage E+ extracts showed a greater propensity for negatively affecting aphids than did E+ extract at maturity and the yellowing stage. These results show that extracts from endophyte-containing plants may contain compounds that may be used to control insects.

Green Synthesis and Characterization of CuO@SiO2 Nanocomposite using Gum Arabic (Acacia senegalensis) (L) against Malaria Vectors

The nanocomposite CuO@SiO2 was synthesized through green pathway using Gum Arabic. The green synthesized nanocomposite was characterized using Scanning Electron Microscopy (SEM), Energy Diffraction X-Ray (EDX), Ultra-Violet/Visible spectroscopy, and Fourier Transform Infra-Red (FTIR). These techniques confirmed the formation of CuO@SiO2 nanocomposite. The toxicity studies were conducted for 24 h on 1st, 2nd, 3rd, and 4th instars of malaria vectors at various concentrations of 10, 20, and 25 Mg/L. The LC50 for the 1st, 2nd, 3rd, and 4th instars were found to be 7.525, 7.980, 8.026 and 9.741 Mg/L, respectively, whilst the LC90 for the 1st, 2nd, 3rd and 4th instars were found to be 14.839, 24.937, 57.77 and 48.5 Mg/L, respectively. The correlation coefficient values between concentrations and mortality for instars were obtained in the range of 0.944 - 0.984. These correlation coefficient values indicate that mortality rates increases with the increase in concentrations. The CuO@SiO2 nanocomposite could be a new nanolarvicide for malaria vector control in tropical countries. HIGHLIGHTS Nanocomposite was synthesized through green Sol gel method using gum Arabic and characterized by Scanning Electron Microscopy (SEM), Energy Diffraction X-Ray (EDX), Ultra-Violet/Visible spectroscopy, and Fourier Transform Infra-Red (FTIR) Larvicidal activity of nanocomposite against Anopheles gambiaecomplex was carried following World Health Organization protocol Probit analysis was conducted to evaluate lethal concentrations (LC50 and LC90) of the nanoparticles against the malaria vectors The CuO@SiO2 nanocomposites could be a potential nanolarvicide for larval source management of malaria vectors GRAPHICAL ABSTRACT

Silencing of Aquaporin Homologue Accumulates Uric Acid and Decreases the Lifespan of the Asian Citrus Psyllid, Diaphorina citri (Hemiptera: Liviidae).

Simple SummaryThe use of RNA interference has become increasingly popular for investigating insect physiology, testing the functionality of insect genes and as a potential control strategy. Hemiptera include many vectors for destructive plant diseases. A major characteristic of the order of Hemiptera is feeding on the phloem sap of their plant hosts. Phloem feeders face high osmotic stress between the gut lumen and hemolymph due to the high level of sucrose in phloem sap. Targeting the osmoregulation mechanisms in Diaphorina citri Kuwayama, which transmits ‘Candidatus Liberibacter asiaticus’, the putative causal agent of Huanglongbing in citrus may lead to an effective control strategy. Herein we downregulate the expression of aquaporin, representing a major mechanism of osmoregulation, by RNA interference.The Asian citrus psyllid, Diaphorina citri Kuwayama is devastating the citrus industry worldwide. It transmits ‘Candidatus Liberibacter asiaticus’, the pathogen of Huanglongbing in citrus. RNA interference is an excellent tool for functional genomics and for screening target genes for pest control. Herein, we silenced the aquaporin (AQP) gene (DcAQP) homologue in D. citri to study its functionality and whether it could be a good target for a control strategy. AQP is an integral membrane channel protein that aids in the rapid flux of water and other small solutes that move across the lipid membrane. In Hemiptera, it is well established that AQP plays important roles in adjusting to physiological challenges including (1) regulating osmotic stress between the gut lumen and hemolymph after imbibing large quantities of a low nitrogen, sugar-rich liquid diet; (2) avoiding or preventing dehydration and desiccation; and (3) surviving at elevated temperatures. The dsRNA-DcAQP was applied twice to nymphs of the 4th and 5th instars through a soaking technique. Silencing AQP caused a significant increase in nymph mortality. Emerged adults showed malformations and a shorter lifespan. Silencing DcAQP provoked alterations in some metabolites and increased the uric acid content in emerged adults. DcAQP could be a useful target to control D. citri.

Scaled-up ethyl formate fumigation to replace methyl bromide on traded mushroom to disinfest mushroom fly (Lycoriella mali)

Mushroom fly, Lycoriella mali (Diptera: Sciaridae), is the primary pest in imported mushrooms. The amount of Tricholoma matsutake imported from China increases every fall when it is harvested. When importing T. matsutake, disinfestation using methyl bromide (MB) or phosphine (PH3) is performed to prevent the introduction of L. mali. However, MB will be phased out due to ozone-depletion, chronic toxicity to workers, and residual issues. PH3 fumigation in mushroom disinfestation requires a long exposure time (24 h). In this study, we used ethyl formate (EF), which can replace MB and reduce exposure time. The efficacy of EF, PH3 and EF + PH3 on L. mali was evaluated. Using 4-h EF fumigation at 5 °C, the 3rd and 4th instar was the most tolerant stage in terms of 99% killed lethal concentration × time products (LCt99%). When 4-h EF fumigation at 5 °C was applied on all stages of L. mali, the LCt99% values of EF were 73.1 g h/m3 to the 1st and 2nd instar, 112.9 g h/m3 to the 3rd and 4th instar, 68.9 g h/m3 to pupae, and 20.1 g h/m3 to adult. It was confirmed that combination treatment with EF + PH3 had a synergistic effect on L. mali. The LCt99% of EF + 0.5 g/m3 of PH3 to the 3rd and 4th instar was 48.3 g h/m3. When only 140 g/m3 of EF was applied for 4 h at > 5 °C and 35 g/m3 of EF + 0.5 g/m3 of PH3 for 4 h at > 5 °C in commercial trials containing T. matsutake, proven efficacy (100%) on L. mali was confirmed. In the case of EF treatment only, phytotoxic damage occurred due to high Ct products, and there was no phytotoxic damage in combination treatment with EF + PH3. This study provides a new guideline for EF + PH3 combination treatment within a shorter exposure time (4 h) than existing PH3 treatment (24 h) and replacement of MB use.

Myrmecomorphy in early nymphs of Acontista concinna (Perty) (Mantodea: Acanthopidae: Acontistini), with notes on a new chromatic form

Summary Ant resemblance is common among praying mantis nymphs but switching the model of resemblance across the post-embryonic instars has been previously recorded only for Mantoida maya Saussure & Zehntner and Acontista aurantiaca (Burmeister). This work describes in detail the myrmecomorphy of early nymphs of Acontista concinna (Perty), based on ample material reared from oothecae collected in the field. Mimic models are proposed, and the possible occurrence of transformational mimicry is discussed. The 1st instar nymphs are defended as mimics of Pseudomyrmex gibbinotus (Forel) (Formicidae), but sudden and intense changes in colour and size during the transition to the 2nd instar make them similar to larger ants, namely Camponotus Mayr. This is maintained throughout the 3rd instar, but disappears on the 4th instar, giving place to typical mantid nymphs. A dark brown chromatic form for females of A. concinna is recorded for the first time, and its existence casts further doubts about the value of overall body colour in separating Acontista Saussure & Zehntner from Raptrix Terra.

Effectiveness Vitamin C on different Characteristics of Silkworm, Bombyx mori L.

In order to investigate effectiveness vitamin C on different characteristics of silkworm, Bombyx mori L. Silkworm larvae through 4th to 5th instar were treated with dietary supplements of ascorbic acid 7000 (VC1) and 10000 (VC2) ppm . Leaves enriched with vitamin C were fed four times per day for the larvae. Results obtained that VC1 of vitamin C is more effective than VC2 and control. It had a significant increase in biological criteria s like larval weight and larval period while economical criteria s like cocoon weight, cocoon shell weight and pupal weight. They weren’t shown any difference between VC1 and VC2 compared to control. Ascorbic acid (VC2) significantly increased the number of Prohaemocytes (Pr) 15, Granulocytes (Gr) 35.3, Plasmatocytes (Pl) 27.6 and Oenocytoides (Oe) 8 cells, respectively. This study was indicated that vitamin C has been effective on increasing the growth rate of larvae, weight of the cocoon and increasing the immunity of larvae. So, It is recommended to using it in the breeding of silkworms and production of silk commercially.

Prey stage preference and functional response of the seven-spot lady beetle Coccinella septempunctata to the rose aphid, Macrosiphum rosivorum

ABSTRACT The rose aphid, Macrosiphum rosivorum (Zhang), is a serious pest of roses in China. Currently, M. rosivorum is managed using almost exclusively with insecticides; therefore, effective, alternative strategies are needed to reduce this dependence on pesticides and the risk of the development of resistance in rose aphids. This study was conducted to evaluate the potential of the seven-spot ladybird, Coccinella septempunctata (L.), as a biological control agent of M. rosivorum in rose production fields. We determined the prey preference of C. septempunctata at constant densities of M. rosivorum for 1st – 4th instar nymphs and for adults. The results showed that Coccinella septempunctata adults had its highest rate of consumption on 4th instars and its lowest rate of consumption on adults among prey life stages. Furthermore, we defined the functional response of predator adults. C. septempunctata adults displayed a type II functional response on all prey stages. The highest attack rate and shortest handling time were for predators fed 1st instar aphids. The proportion of prey consumed by C. septempunctata was higher at lower densities for all stages of rose aphid, implying that C. septempunctata should be released early in an aphid infestation. Our study indicated that C. septempunctata has the potential to be used for control of rose aphids in rose-production fields.

Sublethal Concentration of Pyriproxyfen Reduces Testicular Connective Tissue Thickness in Euschistus heros Fabr. (Hemiptera: Pentatomidae)

The aim of this study was to determine the effect of the insecticide pyriproxyfen (Tiger™ 100 CE), juvenile hormone analogue, when applied in a sublethal LC30 concentration (0.668 mL a. i. L-1), on the morphological and morphometric parameters of external and internal connective tissue (CT) of the Neotropical-brown stink bug Euschistus heros testicles. The insecticide was applied on nymphs from the 4th instar using a Potter tower with a working pressure of 82.73 kPa (12 lb pol-²) and 1 mL of the emulsion per replicate. A completely randomized experimental design was used, consisting of two treatments (control and pyriproxyfen-treated), five repetitions, and 10 adults of E. heros per experimental unit. The insects were maintained under controlled conditions until the emergence of adults. After 48 h of emergence of adults, the testicles were collected, fixed, and processed for morphological and morphometric analyses. A change was observed in the collagen fibers of the CT of treated insects when compared with those of controls. It was also observed that both types of CT (dense irregular and loose) over the internal tunic of the treated insect were thinner than those in control insects. The analysis showed that pyriproxyfen significantly reduced the external and internal CT width and the conformation of its fibers in all the observed regions when compared with the controls; this may affect the production of the three different types of sperm present in this species.

Susceptibility of the fall armyworm, Spodoptera frugiperda (J.E. Smith, 1797) (Lepidoptera: Noctuidae), to four species of entomopathogenic nematodes (Steinernematidae and Heterorhabditidae) from Mizoram, North-Eastern India

BackgroundOutbreak of the fall armyworm Spodoptera frugiperda (J.E. Smith, 1797) (Lepidoptera: Noctuidae) occurred in Mizoram, North-Eastern India. The infestation spread in the entire state covering a total area of around 2840 hectares of maize cultivated land. Entomopathogenic nematodes (EPNs) represent potential candidates for the biological control of S. frugiperda. In the study, the susceptibility of the pest against 4 locally isolated EPN species Heterorhabditis indica, H. baujardi, Steinernema sangi and S. surkhetense was evaluated.ResultsThe results indicated that all the isolated EPN species showed a high rate of larvicidal and pupicidal activities against the pest. Mortality between 43.75–100.00 and 25.00–100.00% of 3rd and 5th larval instars, respectively (at concentrations 10–800 IJs/larva), and 37.50–68.75% mortality of pupae (at concentrations 200–1600 IJs /pupa) were found after exposure to the EPN species. The mortality rate of the pest showed significant variations with life stages of the host insect, nematode concentrations and incubation time. Based on the median lethal concentration (LC50), H. indica was the most pathogenic species, followed by S. sangi, H. baujardi and S. surkhetense. The LC50 values of H. indica at 72 h post-incubation were 20.26 and 62.07 IJs/larva for the 3rd and 5th larval instars, respectively, and 913.34 IJs/pupa. The penetration assay showed that H. indica had the highest penetration rate into the hosts, 27.24, 21.30 and 20.00% in the 3rd, 5th larval instars and pupae, respectively. Furthermore, all the EPN isolates were capable of successful multiplication inside the cadaver of S. frugiperda that showed significant differences with the EPN isolates and life stages of the pest. Among the isolates, H. indica showed the highest multiplication rates, 17,692.25 ± 2103.59, 8345.63 ± 785.34 and 79,146.38 ± 5943.73 IJs per 3rd instar larva, 5th instar larva and pupa, respectively.ConclusionsThe study revealed that the 4 species of EPNs showed a high potency against S. frugiperda, thereby having the potential to be developed as a biological control agent against the pest. Moreover, the isolated EPN species could potentially serve as alternatives for chemical insecticides and could further be incorporated into the Integrated Pest Management (IPM).

A deadly encounter: Alien invasive Spodoptera frugiperda in Africa and indigenous natural enemy, Cotesia icipe (Hymenoptera, Braconidae).

The invasion and wide spread of Spodoptera frugiperda represent real impediments to food security and the livelihood of the millions of maize and sorghum farming communities in the sub-Saharan and Sahel regions of Africa. Current management efforts for the pest are focused on the use of synthetic pesticides, which are often economically unviable and are extremely hazardous to the environment. The use of biological control offers a more economically and environmentally safer alternative. In this study, the performance of the recently described parasitoid, Cotesia icipe, against the pest was elucidated. We assessed the host stage acceptability by and suitability for C. icipe, as well as its ovigenic status. Furthermore, the habitat suitability for the parasitoid in the present and future climatic conditions was established using Maximum Entropy (MaxEnt) algorithm and the Genetic Algorithm for Rule‐set Prediction (GARP). Cotesia icipe differentially accepted the immature stages of the pest. The female acceptance of 1st and 2nd instar larvae for oviposition was significantly higher with more than 60% parasitism. No oviposition on the egg, 5th and 6th larval instars, and pupal stages was observed. Percentage of cocoons formed, and the number of emerged wasps also varied among the larval stages. At initial parasitism, parasitoid progenies, time to cocoon formation and overall developmental time were significantly affected by the larval stage. Egg-load varied significantly with wasp age, with six-day-old wasps having the highest number of mature eggs. Ovigeny index of C. icipe was 0.53. Based on the models, there is collinearity in the ecological niche of the parasitoid and the pest under current and future climate scenarios. Eastern, Central and parts of coastal areas of western Africa are highly suitable for the establishment of the parasitoid. The geographic distribution of the parasitoid would remain similar under future climatic conditions. In light of the findings of this study, we discuss the prospects for augmentative and classical biological control of S. frugiperda with C. icipe in Africa.

Riders on the storm? A short note on the biology of Severinia turcomaniae (Saussure, 1872) (Mantodea: Toxoderidae)

Summary New data are presented on the nymphal biology of a praying mantis, Severinia turcomaniae (Saussure, 1872), which has recently spread to the deserts of the Lower Volga Region. Nymphs of 3rd and 4th instars can be encountered in masses in August, suggesting a very short egg development period. They display a clear habitat preference for the tumbleweeds of Ceratocarpus arenarius L. It is hypothesized that the latter may serve for S. turcomaniae nymphs as a unique and efficient means for long-range dispersal and colonization of new localities, which would explain the fast colonization of the territories west of the Volga by S. turcomaniae, but not by Rivetina nana Mistshenko, 1967, another recent invader.

Identification and Virulence of Cordyceps javanica Strain wf GA17 Isolated From a Natural Fungal Population in Sweetpotato Whiteflies (Hemiptera: Aleyrodidae).

A new strain of the entomopathogenic fungus, identified as Cordyceps javanica (Frieder. & Bally) Kepler, B. Shrestha & Spatafora (Hypocreales: Cordycipitaceae) wf GA17, was found naturally infecting the sweetpotato whitefly, Bemisia tabaci (Gennadius) MEAM1 in southern Georgia, US, in September 2017. The fungus was tested for pathogenicity and virulence in comparison with commercially available entomopathogenic fungal strains against several insect species in the laboratory. In specific, it was compared with Cordyceps fumosorosea (Wize) Kepler, B. Shrestha & Spatafora (Hypocreales: Cordycipitaceae) Apopka 97, Beauveria bassiana (Bals.-Criv.) Vuill. (Hypocreales: Cordycipitaceae) strain GHA, and Metarhizium brunneum Petch (Hypocreales: Clavicipitaceae) strain F52 for virulence against B. tabaci (4th instars) and cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae) (4th instars with or without wingbuds), on leaf-discs, and against last instars of pecan weevil Curculio caryae (Horn) (Coleoptera: Curculionidae) and citrus root weevil Diaprepes abbreviatus (L.) (Coleoptera: Curculionidae) in soil cups. Against B. tabaci, C. javanica exhibited higher mortality and mycosis development at 5 d post inoculation than other fungi. In assays against A. gossypii with and without wingbuds, C. javanica and C. fumosorosea had the highest mortality and mycosis levels and B. bassiana had the lowest; nymphs with wingbuds were more susceptible to some fungal infection than those without. Against C. caryae, B. bassiana was more effective than other fungi. For D. abbreviatus, B. bassiana also caused the highest mortality while M. brunneum had the lowest, with Cordyceps spp. being intermediate. Overall, the findings suggest high potential of the new strain, C. javanica wf GA17, for managing whiteflies and aphids, while it was not as effective as B. bassiana against the curculionids.

Fitness comparison of Plutella xylostella on original and marginal hosts using age-stage, two-sex life tables.

The diamondback moth, Plutella xylostella, is an important agricultural pest that severely damages cruciferous vegetables. Although previously considered a threat only to Brassica species, P. xylostella has been observed to feed on noncruciferous vegetables. Here, we established a population of P. xylostella on the pea Pisum sativum (PxP population). We compared this PxP population's performance on the pea host plant to a population (PxR) reared on the original host plant radish (Raphanus sativus) for several generations using an age‐stage, two‐sex life table and analyzed the correlations between different fitness parameters. In the 1st generation of the PxP population, survival rate of immature stage was 17%, while the survival rate of PxR was 68%; the duration of the 4th larval instar (5.30 d) and mortality (25%) of this generation were significantly longer (2.8 d) and higher (1%) than that of PxR, respectively (both p < .001). Upon long‐term acclimation, the PxP fitness improved significantly, especially that the survival rate of immature stages increased to approximately 60% in the 15th, 30th, and 45th generations. However, PxP feeding on pea exhibited poorer fitness with longer larval developmental time, shorter total life span, lighter pupa, and lower fecundity in different generations compared with PxP feeding on radish. PxP feeding on pea also showed a significantly lower intrinsic rate of increase (r), net reproduction rate (R 0), finite increase rate (λ), and longer mean generation time (T) than PxP feeding on radish in all generations tested. Significant positive correlations were observed between pupal weight and female fecundity in pea‐fed populations, and between female longevity and female fecundity in pea‐fed and radish‐fed populations. Our findings suggest that P. xylostella adaptation to pea does not improve overall fitness compared with the original host radish, making pea a marginal host for P. xylostella.