Elevated CO2 and temperature alter development and food utilization of Spodoptera litura fed on resistant soybean

Effects of elevated atmospheric CO₂ (elevated CO₂ vs. ambient CO₂) and temperature (+0.67–0.79°C vs. ambient temperature) on the developmental life cycle of Spodoptera litura and the food utilization of the fourth‐instar larvae fed on soybean (resistant cultivar Lamar vs. susceptible landrace JLNMH) grown in open‐top chambers were studied from 2013 to 2015. The results indicated that: (i) compared with ambient CO₂, elevated CO₂ significantly prolonged the duration of larva and pupa, and adult longevity; significantly decreased the pupation rate, pupal weight, fecundity, the relative growth rate (RGR), efficiency of conversion of ingested food (ECI) and efficiency of conversion of digested food (ECD); and increased the relative consumption rate (RCR) and approximate digestibility (AD). (ii) Compared with ambient temperature, elevated temperature significantly shortened the duration of larva and pupa; significantly decreased the pupal weight; and increased the RGR, RCR, ECD and ECI. (iii) Compared with the susceptible soybean accession JLNMH, the resistant soybean cultivar Lamar significantly prolonged the duration of larva and pupa; significantly decreased the pupation rate, pupal weight, adult longevity, fecundity and RGR, RCR and AD; and increased the indexes of ECD. (iv) At elevated temperature, S. litura fed on resistant vs. susceptible cultivars showed opposite trends in the RGR, RCR, AD, ECD and ECI. In addition, elevated temperature under elevated CO₂ significantly decreased the RGR (2014), ECD (2013 & 2014) and ECI (2013) and increased the AD (2013 & 2014) compared with other treatment combinations when S. litura fed on Lamar. Future climatic change of temperature and CO₂ concentration would likely affect growth and food utilization of S. litura, with increased food intake, but the reduced fecundity may compensate for the increased food consumption, resulting in no significant reduction in insect‐induced yield loss in soybean production. Nevertheless, use of insect resistant soybean cultivars will aid in ecological management of S. litura and reduce the insecticide load in soybean production.     

Toxicity of spinosad and Beauveria bassiana to the black cutworm,and the additivity of subletal doses

The main objective of this study was to assess the susceptibility of the black cutworm (Agrotis ipsilon) to the biopesticide spinosad and to a commercial formulation (GHA strain) of the entomopathogenic fungus, Beauveria bassiana. Secondly, we quantified the effects of sublethal doses of spinosad on a number of A. ipsilon fitness parameters, and interactions resulting from simultaneous applications of sub-lethal doses of spinosad and B. bassiana. Under laboratory conditions, A. ipsilon third instar larvae were highly susceptible to spinosad, with an estimated LC₅₀ of 50 ppm. The entomopathogenic fungus, B. bassiana had a lower efficacy with an estimated LC₅₀ of 7×107 spores mL^?1. Topical applications of 5, 7.5 and 10 ppm of spinosad on third instar larvae reduced larval size and increased time to pupation and to emergence. However, pupal and adult weights were not significantly different between treated and control individuals. Additivity was observed from most spinosad–B. bassiana combinations tested, thus indicating compatibility between products. We concluded that spinosad is a promising tool for controlling black cutworm larvae alone or in combination with other products.     

Genetics of resistance to Cry1C toxin from Bacillus thuringiensis in Spodoptera litura (Fab.)

The present study was undertaken to determine the genetics of Cry1C resistance in Spodoptera litura. Selection of S. litura (Fab.) with Cry1C was done for eight generations to develop resistance. Reciprocal crosses between resistant and susceptible populations were made to understand the population genetics of Cry1C resistance in S. litura. Generation wise selection with Cry1C was evaluated for resistance development in S. litura. The LC₅₀ of Cry1C was 0.14 µg/cm² for the first selected generation and it increased to 23.98 µg/cm² after eight selected generations, which is a 285.47-fold increase in resistance compared with the susceptible strain. The estimated realized heritability (h²) after eight generations of selection with Cry1C insecticidal protein was 0.44. The number of generations required for the tenfold increase in LC₅₀ (1/R) was estimated to be 3.33. Response to Cry1C selection in S. litura was 0.30, the estimated selection differential was 0.69 and the pheonotypic standard deviation (dP) was 0.24. Reciprocal crosses between Cry1C resistant and susceptible strain of S. litura showed autosomal resistance.     

Some Biochemical Abnormalities Caused by Cypermethrin in Adults of Tribolium castaneum (Herbst.)

Biochemical effects of sub lethal doses LC₁₀ and LC₂₀ of cypermethrin were studied on some enzymes and macromolecule activities of adult beetles of Tribolium castaneum (Herbst.). Cypermethrin caused disturbances in levels of all biochemical components under study. The dose of 0.78 ppm caused abnormalities in α‐amylase and FAA by increasing their activities i.e., 45.45% and 21.97% significantly. The higher sub lethal dose of 2.62 ppm disturbed all the parameters (AcP, α‐amylase, soluble protein and FAA) except AkP, which was decreased by 93.06%. Moreover, sub lethal doses either increased or decreased the levels of all parameters non‐significantly except AkP and FAA which were effected significantly by 87.92% and 14.29% at lower and higher doses, respectively. In the present studies, cypermethrin significantly enhanced the activity of AkP in both susceptible and resistant strains of T. castaneum adult beetles while FAA contents were increased significantly in resistant strain only. The activity of α‐amylase was significantly lowered in susceptible strain only.     

Impact of spinosad on ichneumonid‐parasitized Choristoneura rosaceana larvae and subsequent parasitoid emergence

The impact of low levels of spinosad on the obliquebanded leafroller, Choristoneura rosaceana Harris (Lepidoptera: Tortricidae), and the koinobiont endoparasitoid, Apophua simplicipes Cresson (Hymenoptera: Ichneumonidae), was assessed when the parasitoid was in the larval stage within second‐ and fourth‐instar hosts. These are developmental stages that would be exposed to spring orchard treatments of the insecticide. Oral spinosad LC₅₀ levels for unparasitized obliquebanded leafroller hosts were <1% of the recommended orchard treatment levels. Apophua simplicipes survival was significantly reduced within parasitized spinosad‐treated second‐ and fourth‐instar larval hosts. Both the leafroller host and parasitoid were much more susceptible (ca. 65‐fold) to spinosad when larval hosts fed on spinosad‐treated leaf material as opposed to being treated topically. When hosts were exposed to extremely low doses of spinosad, a small percentage of parasitoids was able to survive to emerge as adults. These laboratory trials predict that applications of spinosad may reduce biological control of C. rosaceana populations by ichneumonid endoparasitoids developing within treated hosts.     

Highly Toxic and Broad-Spectrum Insecticidal Bacillus thuringiensis Engineered by Using the Transposon Tn917 and Protoplast Fusion

The chromosome of the Bacillus thuringiensis strain S184 that was toxic against the third instar larvae of Spodoptera litura with the LC₅₀ of 9.74 μg/ml was successfully integrated into two genes of cyt1Aa and cry11Aa using the transposon Tn917, yielding the primary engineered strain TnX. The strain TnX was highly toxic to the third instar larvae of Culex pipiens fatigans with the LC₅₀ of 5.12 ng/ml which was 1.82-fold higher than that of B. thuringiensis subsp. israelensis, but lowly toxic to lepidopterous larvae. By the protoplast fusion of the strain TnX and the strain S184-Tet^r (resistance to tetracycline), the target engineered strain TnY was obtained. Against the third instar larvae of S. litura, the strain TnY LC₅₀ was of 4.68 μ g/ml and increased by 2.08-fold in comparison with the parent strain S184. Against the third instar larvae of C. pipiens fatigans, the strain TnY LC₅₀ was of 103.20 ng/ml. The two target genes of cyt1Aa and cry11Aa integrated into the chromosome were extremely stable and had little possibility of a second transposition. It was unclear whether some factors existing in the parent strain, S184, contributed to the high toxicity of the strains TnX and TnY. Received: 30 November 2000 / Accepted: 10 January 2001     

Biocontrol efficacy of protoplast fusants between Bacillus thuringiensis and Bacillus subtilis against Spodoptera litura Fabr.

Bacillus thuringiensis (Bt) is a microbial pesticide widely used to control crop pests. Its strains have good biocontrol activity against crop insect pest, but lack some desirable characteristics that are found in Bacillus subtilis. An attempt has been made to combine those desirable characteristics; we used a highly effective biocontrol strain of B. thuringiensis in protoplast fusions with a strain of B. subtilis. The fusants were identified through cell culture and stained with crystal violet. The Bt and B. subtilis protoplasts were induced to fuse by PEG 6000. The fusants were produced almost 95% mortality in first instar larvae of Spodoptera litura. The lethal doses (The LC₅₀ and LC₉₀) for mortality of S. litura values were significantly in lower level in the fusant-treated larvae, when compared with Bt and B. subtilis individual treatment. The consumption and digestion of S. litura significantly decreased after treatment with fusant. Also the approximate digestibility of S. litura increased significantly.     

金龟子绿僵菌对斜纹夜蛾幼虫的生防效果、抗氧化酶活性和肠道细菌群落的影响

【目的】测定金龟子绿僵菌(Metarhizium anisopliae)对斜纹夜蛾(Spodoptera litura) 2龄幼虫的毒力,研究金龟子绿僵菌侵染后寄主体内抗氧化酶活性和肠道内细菌群落的变化,探讨斜纹夜蛾对金龟子绿僵菌侵染的防御机制。【方法】采用浸渍法测定不同浓度金龟子绿僵菌对斜纹夜蛾2龄幼虫的毒力;应用IlluminaMiSeq高通量测序技术测定肠道细菌群落。【结果】不同浓度的孢悬液对斜纹夜蛾2龄幼虫均有一定的毒力,处理7 d时半致死浓度(LC₅₀)为3.944 107个孢子/mL;浓度为1.0×10⁹个孢子/mL时,半致死时间最短(LT₅₀)为4.6 d,校正后的死亡率为81.03%。处理后未致死的斜纹夜蛾幼虫体内抗氧化酶活性显著高于对照组。处理后致死的斜纹夜蛾幼虫肠道细菌群落多样性显著高于对照组;且处理后致死的斜纹夜蛾幼虫肠道细菌群落组成与对照组差异显著。【结论】金龟子绿僵菌对斜纹夜蛾幼虫的致死率和致死效率与金龟子绿僵菌的浓度呈正相关;斜纹夜蛾幼虫体内的抗氧化酶可能在抵抗金龟子绿僵菌侵染的过程中起重要作...     

Insecticide Susceptibilities of Anopheles sinensis (Diptera: Culicidae) Larvae from Paju-shi, Korea

A study was conducted to determine the susceptibility of Anopheles sinensis larvae, malaria vector, from Paju‐shi (Gyonggi‐do) to 24 pesticides including 11 pyrethroids, 11 organophosphates, 1 pyrazole analogue and another pesticide. The mosquito larvae showed the most highly susceptible to chlorfenapyr with LC₅₀ of 0.0063 ppm followed by spinosad, temephos, fenthion and beta‐cyfluthrin with 0.03, 0.0366, 0.0367 and 0.0998 ppm, respectively, and fluvalinate (>128 ppm) was the least susceptible. Also, 11 pesticides of them were compared with Goyang strain (Gyonggi‐do) of data 1992. The development of resistance was noticed to cypermethrin and permethrin as much of 73.59 and 6.23 folds at LC₅₀, respectively, and also fluvalinate was showed high resistance development. In generally, the pyrethroid insecticides were showed higher development of resistance than organophosphorus insecticides.     

Acute toxicity and sub-lethal effects of a pyrethroid (cypermethrin) on survival,development and fitness of Helicoverpa armigera

The chickpea pod borer, Helicoverpa armigera (Hübner) is one of the most destructive pests of India and most of the countries. In this experiment, sub-lethal effects of cypermethrin were evaluated against sixth instar larvae of this pest that had ingested insecticide-treated chickpea pods. The LC₅₀, LC₃₀ and LC₁₀ values of cypermethrin were 80.38, 26.65 and 5.41?mg a.i.?L^?1, respectively, against sixth instar. The sub-lethal effects on fitness, eggs, larvae, pupae, adult longevity and reproduction were observed in H. armigera population that survived exposure to the sub-lethal doses of LC₅₀, LC₃₀ and LC₁₀ of cypermethrin. Survivorship was reduced to 36?days if H. armigera exposed to the sub-lethal dose of LC_50, whereas it was 42?days in unexposed groups. Larvae treated with LC₅₀ dose exhibit lowest intrinsic rate of increase (r_m) (0.0413 females/female/day) and highest (0.0517) with the unexposed group. Time taken by H. armigera to complete one generation (T_c) was 40.09?days, while this time significantly lowered to 32.85?days when exposed to the sub-lethal dose of LC₃₀. Hatching eggs were greatly reduced in the larvae exposed to cypermethrin at all the sub-lethal doses. About 430 eggs/female/generation were recorded after treatment with 80.38?mg/L as compared with untreated females (1390). Larvae that were exposed to sub-lethal concentrations of cypermethrin exhibited lower pupal weight and prolonged pupal developmental times compared control larvae. The overall fitness performance was better in the unexposed population as compared to the population exposed to sub-lethal doses.     

Chemical composition and larvicidal activity of edible plant‐derived essential oils against the pyrethroid‐susceptible and ‐resistant strains of Aedes aegypti (Diptera: Culicidae)

The chemical compositions and larvicidal potential against mosquito vectors of selected essential oils obtained from five edible plants were investigated in this study. Using a GC/MS, 24, 17, 20, 21, and 12 compounds were determined from essential oils of Citrus hystrix, Citrus reticulata, Zingiber zerumbet, Kaempferia galanga, and Syzygium aromaticum, respectively. The principal constituents found in peel oil of C. hystrix were β‐pinene (22.54%) and d‐limonene (22.03%), followed by terpinene‐4‐ol (17.37%). Compounds in C. reticulata peel oil consisted mostly of d‐limonene (62.39%) and γ‐terpinene (14.06%). The oils obtained from Z. zerumbet rhizome had α‐humulene (31.93%) and zerumbone (31.67%) as major components. The most abundant compounds in K. galanga rhizome oil were 2‐propeonic acid (35.54%), pentadecane (26.08%), and ethyl‐p‐methoxycinnamate (25.96%). The main component of S. aromaticum bud oil was eugenol (77.37%), with minor amounts of trans‐caryophyllene (13.66%). Assessment of larvicidal efficacy demonstrated that all essential oils were toxic against both pyrethroid‐susceptible and resistant Ae. aegypti laboratory strains at LC₅₀, LC₉₅, and LC₉₉ levels. In conclusion, we have documented the promising larvicidal potential of essential oils from edible herbs, which could be considered as a potentially alternative source for developing novel larvicides to be used in controlling vectors of mosquito‐borne disease.     

Sublethal effects of hexaflumuron on development and reproduction of the diamondback moth,Plutella xylostella (Lepidoptera: Yponomeutidae)

Abstract Effects of hexaflumuron at 10% lethal concentration (LC₁₀) and LC₂₅ on development and reproduction parameters of the diamondback moth, Plutella xylostella (Linnaeus, 1753) (Lep.: Yponomeutidae) were investigated. Estimated LC₅₀, LC₁₀ and LC₂₅ values of leaf dip bioassay of hexaflumuron on the third instar larvae of the P. xylostella were 1.48, 0.59 and 0.91 mg/L, respectively. Hexaflumuron decreased pupal weight in the parent generation at sublethal concentrations but in the offspring generation, this effect was not observed. Sublethal concentrations increased egg, first and second larval instar and pupa developmental time and shortened life span of adults, but did not change the third and fourth larval instars and pre‐pupa developmental period. Also fecundity of females reduced significantly but hatchability of treatments and control were similar. Survival rate of pre‐adult stages declined significantly at LC₂₅ concentration. Reproduction parameters such as reproductive rate (R₀) and intrinsic rate of increase in sublethal concentrations were significantly lower compared with control, but gross reproduction rate (GRR) at the LC₁₀ concentration was increased and it could be hormoligosis. Also hexaflumuron significantly increased doubling time (Dt). We conclude that the sublethal effects of hexaflumuron might exhibit significant effects on the population dynamics of P. xylostella.     

Specificity of herbivore‐induced responses in an invasive species,Alternanthera philoxeroides (alligator weed)

Herbivory‐induced responses in plants can both negatively affect subsequently colonizing herbivores and mitigate the effect of herbivory on the host. However, it is still less known whether plants exhibit specific responses to specialist and generalist herbivores in non‐secondary metabolite traits and how specificity to specialists and generalists differs between invasive and native plant populations. We exposed an invasive plant, Alternanthera philoxeroides, to Agasicles hygrophila (Coleoptera, Chrysomelidae; specialist), Spodoptera litura (Lepidoptera, Noctuidae; generalist), manual clipping, or application of exogenous jasmonic acid and examined both the specificity of elicitation in traits of fitness (e.g., aboveground biomass), morphology (e.g., root:shoot ratio), and chemistry (e.g., C/N ratio and lignin), and specificity of effect on the subsequent performance of A. hygrophila and S. litura. Then, we assessed variation of the specificity between invasive and native populations (USA and Argentina, respectively). The results showed S. litura induced higher branching intensity and specific leaf area but lower C/N ratio than A. hygrophila, whereas A. hygrophila induced higher trichome density than S. litura. The negative effect of induction on subsequent larval growth was greater for S. litura than for A. hygrophila. Invasive populations had a weaker response to S. litura than to A. hygrophila in triterpenoid saponins and C/N ratio, while native populations responded similarly to these two herbivores. The specific effect on the two herbivores feeding on induced plants did not vary between invasive and native populations. Overall, we demonstrate specificity of elicitation to specialist and generalist herbivores in non‐secondary metabolite traits, and that the generalist is more susceptible to induction than the specialist. Furthermore, chemical responses specific to specialist and generalist herbivores only exist in the invasive populations, consistent with an evolutionary change in specificity in the invasive populations.     

响应面法优化爪哇虫草菌的培养条件及其对斜纹夜蛾的毒力和保护酶活性影响

【目的】优化爪哇虫草菌Bd01的固态发酵培养条件,测定分生孢子对斜纹夜蛾3龄幼虫的毒力,研究被爪哇虫草菌侵染后寄主体内的保护酶活性变化。【方法】采用单因素试验确定爪哇虫草菌Bd01最佳的固态培养基及培养条件,利用Box-Behnken响应面法优化发酵参数,采用浸渍法测定分生孢子对斜纹夜蛾3龄幼虫的毒力,同时利用分光光度计法测定斜纹夜蛾3龄幼虫体内酶活性变化。【结果】以产孢量为指标,通过响应曲面法优化的爪哇虫草菌Bd01最佳产孢条件为：培养基营养成分含量为30.24g/L,pH值为7.55,光照时长为12.06h,在该条件下,培养基的产孢量为2.78×10⁸孢子/mL。浓度为1×10⁸孢子/mL的爪哇虫草菌孢子液对斜纹夜蛾3龄幼虫具有一定毒力,处理7 d时致死中浓度(LT₅₀)为3.11 d,致死中时(LC₅₀)为4.68×10⁵孢子/mL,校正死亡率为88.68%。处理后未死亡的斜纹夜蛾幼虫体内保护酶活性与对照组相比发生显著变化。【结论】优化后的培养基能够显著增加爪哇虫草菌的产...     

Insecticidal and antifungal potentials of a proteinaceous extract of Cassia occidentalis (Linn.) seeds

Proteinaceous extract obtained from Cassia occidentalis seeds with purification fold of 3.91 and 82.7% of bovine trypsin inhibitory activity was assessed at different concentrations (25, 50, 100, 200, 400 and 800 μg/ml) against Spodoptera litura. Assay of larval feeding suggested proteinaceous extract to be toxic as prepupal (80.16%) and pupal mortalities (100%) along with growth deterrent effect with only 16.71% pupation was observed at 800 μg/ml. Fifty per cent mortality (LC₅₀) was observed at 132.91 μg/ml. Also the inhibitor affected fecundity, longevity and percentage of egg hatching. Nutritional indices were adversely affected as both efficiency of conversion of ingested and digested food decreased while approximate digestibility and metabolic cost increased. In vitro studies on proteolytic enzymes of S. litura revealed inhibition of trypsin and chymotrypsin in lumen and faecal matter at all tested concentrations. Also proteinaceous extract inhibited mycelial growth in Fusarium oxysporum, Alternaria brassicicola and Alternaria alternata at 100 μg/ml.     

Evaluations of larvicidal activity of medicinal plant extracts to Aedes aegypti （Diptera： Culicidae） and other effects on a non target fish

A preliminary study was conducted to investigate the effects of the extracts of 112 medicinal plant species, collected from the southern part of Thailand, on Aedes aegypti. Studies on larvicidal properties of plant extracts against the fourth instar larvae revealed that extracts of 14 species showed evidence of larvicidal activity. Eight out of the 14 plant species showed 100% mosquito larvae mortality. The LC50 values were less than 100μg/mL （4.1μg/ mL-89.4μg/mL）. Six plant species were comparatively more effective against the fourth instar larvae at very low concentrations. These extracts demonstrated no or very low toxicity to guppy fish （Poecilia reticulata）, which was selected to represent most common non-target organism found in habitats ofAe. aegypti, at concentrations active to mosquito larvae. Three medicinal plants with promising larvicidal activity, having LC50 and LC50 values being 4.1 and 16.4 μg/mL for Mammea siamensis, 20.2 and 34.7 μg/mL forAnethum graveolens and 67.4 and 110.3μg/mL forAnnona muricata, respectively, were used to study the impact of the extracts on the life cycle ofAe. aegypti. These plants affected pupal and adult mortality and also affected the reproductive potential of surviving adults by reducing the number of eggs laid and the percentage of egg hatchability. When each larval stage was treated with successive extracts at the LC50 value, the first instar larvae were found to be very susceptible to A. muricata and the second instar larvae were found to be susceptible to A. graveolens, while the third and fourth instar larvae were found to be susceptible to M. siamensis. These extracts delayed larval development and inhibited adult emergence and had no adverse effects on P. reticulata at LC50 and LC50 values, except for the M. siamensis extract at its LC50 value.     

Toxicity of chlorpyrifos‐methyl to Sitophilus zeamais collected in Korea and biochemical differences

In this study, lethal concentration (LC₅₀) values of chlorpyrifos‐methyl (CPM) were determined for two Korean strains (CBNU and KNU) of Sitophilus zeamais. The two strains had similar susceptibilities (1.70 and 1.86 μg a.i./cm², respectively) to CPM. Carboxylesterase (CE) activity was twice as high in the CBNU strain as in the KNU strain. Lower acetylcholinesterase (AChE) activity was also noted in the latter; however, the activity of glutathione S‐transferase (GST) was twice as high as in the CBNU strain. Gel electrophoresis of CE of crude extracts from adults of the two strains of S. zeamais showed clearly different band patterns, with molecular weights of 60 kDa and 71 kDa in the CBNU and KNU strains, respectively. MALDI‐TOF MS/MS was used to profile small proteins (less than 10 kDa), with results indicating that 206 proteins are expressed differently in the two strains. The peak of interest of 2247.7 m/z was applied to TOF‐TOF MS and its de novo peptide sequence was identified as a tyrosine phosphatase fragment. Phospholipids from the two strains were analyzed and 34 phospholipids were found to be significantly different between strains. Results suggest that the two strains collected from Korea showed different biochemical results, presumably differences in insecticide selection by different living locations.