Rapid Identification of Helicoverpa armigera and Helicoverpa zea (Lepidoptera: Noctuidae) Using Ribosomal RNA Internal Transcribed Spacer 1

Rapid identification of invasive species is crucial for deploying management strategies to prevent establishment. Recent Helicoverpa armigera (Hübner) invasions and subsequent establishment in South America has increased the risk of this species invading North America. Morphological similarities make differentiation of H. armigera from the native Helicoverpa zea (Boddie) difficult. Characteristics of adult male genitalia and nucleotide sequence differences in mitochondrial DNA are two of the currently available methods to differentiate these two species. However, current methods are likely too slow to be employed as rapid detection methods. In this study, conserved differences in the internal transcribed spacer 1 (ITS1) of the ribosomal RNA genes were used to develop species-specific oligonucleotide primers that amplified ITS1 fragments of 147 and 334 bp from H. armigera and H. zea, respectively. An amplicon (83 bp) from a conserved region of 18S ribosomal RNA subunit served as a positive control. Melting temperature differences in ITS1 amplicons yielded species-specific dissociation curves that could be used in high resolution melt analysis to differentiate the two Helicoverpa species. In addition, a rapid and inexpensive procedure for obtaining amplifiable genomic DNA from a small amount of tissue was identified. Under optimal conditions, the process was able to detect DNA from one H. armigera leg in a pool of 25 legs. The high resolution melt analysis combined with rapid DNA extraction could be used as an inexpensive method to genetically differentiate large numbers of H. armigera and H. zea using readily available reagents.     

Comparative Feeding Performance and Digestive Physiology of Helicoverpa armigera (Lepidoptera: Noctuidae) Larvae-Fed 11 Corn Hybrids

This study aimed to evaluate the feeding responses and digestive proteolytic and amylolytic activity of Helicoverpa armigera (Hübner) on 11 corn (Zea mays L.) hybrids at 25 ± 1°C, 65 ± 5% relative humidity (RH), and a photoperiod of 16:8 (L:D) h. The fourth- and fifth-instar larvae fed on hybrid K47*K19 had the highest weight of food consumption and those reared on hybrid KSC705 had the lowest value of food consumption. The highest weight gain of the larvae was observed when H. armigera were fed hybrid KLM78*MO17 and lowest when they were fed hybrids K36 * MO17, KSC705, and K35 * K36. Pupal weight of H. armigera was heaviest when larvae were fed hybrid K47*K19 and lightest when they were fed hybrid KSC705. The highest proteolytic activity of the fourth-instar larvae was observed when they were fed hybrid KSC705, and the lowest activity was observed when they were fed hybrid K47*A67. Fifth-instar larvae that fed on hybrid K47*K19 showed the highest proteolytic activity. Fourth-instar larvae that fed on hybrid K36*MO17 showed the highest amylase activity. The fifth-instar larvae fed on hybrid K47*A67 showed the maximum amylase activity and those reared on the K48*K18 showed the minimum activity. Our results indicated that K36 * MO17, KSC705, and K48 * K18 were the most unsuitable hybrids for feeding H. armigera.     

Adaptation of Habrobracon hebetor (Hymenoptera: Braconidae) to Rearing on Ephestia kuehniella (Lepidoptera: Pyralidae) and Helicoverpa armigera (Lepidoptera: Noctuidae)

Food characteristics strongly regulate digestive enzymatic activity of insects through direct influences on their midgut mechanisms. Insect performance is better on diets that contain nutrients in proportions that fit its digestive enzymes. Little is known about the influences of rearing history on parasitism success of Habrobracon hebetor Say. This research focused on the effect of nutrient regulation on survival, development, and parasitism of H. hebetor. Life history and digestive enzyme activity of fourth-stage larvae of H. hebetor were studied when reared on Ephestia kuehniella Zeller. This parasitoid was then introduced to Helicoverpa armigera (Hübner), and above-mentioned parameters were also studied in the first and fourth generations after transfer. In term of parasitism success, H. hebetor preferred E. kuehniella over He. armigera. When the first and fourth generations of He. armigera-reared H. hebetor were compared, the rearing history affected the life history and enzymatic activity of the parasitoid. A better performance of H. hebetor was achieved after it was reared on He. armigera for the four generations. Because, digestive α-amylase and general protease of the parasitoid were matched with the new host, it used reserve energy for a better performance. Thus, a better performance of H. hebetor could be obtained when the parasitoid was reared on its original host for at least four generations.     

Helicoverpa zea (Lepidoptera: Noctuidae) and Spodoptera frugiperda (Lepidoptera: Noctuidae) Responses to Sorghum bicolor (Poales: Poaceae) Tissues From Lowered Lignin Lines

The presence of lignin within biomass impedes the production of liquid fuels. Plants with altered lignin content and composition are more amenable to lignocellulosic conversion to ethanol and other biofuels but may be more susceptible to insect damage where lignin is an important resistance factor. However, reduced lignin lines of switchgrasses still retained insect resistance in prior studies. Therefore, we hypothesized that sorghum lines with lowered lignin content will also retain insect resistance. Sorghum excised leaves and stalk pith Sorghum bicolor (L.) Moench (Poales: Poaceae) from near isogenic brown midrib (bmr) 6 and 12 mutants lines, which have lowered lignin content and increased lignocellulosic ethanol conversion efficiency, were examined for insect resistance relative to wild-type (normal BTx623). Greenhouse and growth chamber grown plant tissues were fed to first-instar larvae of corn earworms, Helicoverpa zea (Boddie) and fall armyworms Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), two sorghum major pests. Younger bmr leaves had significantly greater feeding damage in some assays than wild-type leaves, but older bmr6 leaves generally had significantly less damage than wild-type leaves. Caterpillars feeding on the bmr6 leaves often weighed significantly less than those feeding on wild-type leaves, especially in the S. frugiperda assays. Larvae fed the pith from bmr stalks had significantly higher mortality compared with those larvae fed on wild-type pith, which suggested that bmr pith was more toxic. Thus, reducing lignin content or changing subunit composition of bioenergy grasses does not necessarily increase their susceptibility to insects and may result in increased resistance, which would contribute to sustainable production.     

Relative Fitness of Helicoverpa armigera (Lepidoptera: Noctuidae) on Seven Host Plants: A Perspective for IPM in Brazil

The cotton bollworm Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) is a widespread pest of many cultivated and wild plants in Europe, Africa, Asia, and Australia. In 2013, this species was reported in Brazil, attacking various host crops in the midwestern and northeastern regions of the country and is now found countrywide. Aiming to understand the effects of different host plants on the life cycle of H. armigera, we selected seven species of host plants that mature in different seasons and are commonly grown in these regions: cotton (Gossypium hirsutum, “FM993”), corn (Zea mays, “2B587”), soybean (Glycine max, “99R01”), rattlepods (Crotalaria spectabilis), millet (Pennisetum glaucum, “ADR300”), sorghum (Sorghum bicolor, “AGROMEN70G35”), and cowpea (Vigna unguiculata, “SEMPRE VERDE”). The development time of immatures, body weight, survivorship, and fecundity of H. armigera were evaluated on each host plant under laboratory conditions. The bollworms did not survive on corn, millet, or sorghum and showed very low survival rates on rattlepods. Survival rates were highest on soybean, followed by cotton and cowpea. The values for relative fitness found on soybean, cotton, cowpea, and rattlepods were 1, 0.5, 0.43, and 0.03, respectively. Survivorship, faster development time, and fecundity on soybean, cotton, and cowpea were positively correlated. Larger pupae and greater fecundity were found on soybean and cotton. The results indicated that soybean, cotton, and cowpea are the most suitable plants to support the reproduction of H. armigera in the field.     

Acute toxicity and sublethal effects of methoxyfenozide and thiodicarb on survival,development and reproduction of Helicoverpa armigera (Lepidoptera: Noctuidae)

The cotton bollworm Helicoverpa armigera (Hubner) is one of the most destructive pest insects in Iran and many other countries. In this study, lethal and sublethal effects of methoxyfenozide, and thiodicarb were evaluated against H. armigera larvae that fed on insecticide-treated artificial diet. The effects of methoxyfenozide and thiodicarb were assessed in 3rd instars. Methoxyfenozide and thiodicarb showed LC₅₀ values of 4 and 639 mg a.i./ml, respectively, in H. armigera larvae. Sublethal effects on development, adult longevity, and reproduction were observed in H. armigera larvae that survived exposure to an LC₃₀ of the insecticides. Larvae that were exposed to an LC₃₀ concentration of methoxyfenozide exhibited lower pupal weight and increased larval and pupal developmental times compared with thiodicarb treated larvae or control larvae. Adults that were exposed as larvae to an LC₃₀ concentration of methoxyfenozide or thiodicarb showed reduced fecundity (35% and 30%, respectively) compared to control adults. The tested insecticides significantly reduced adult longevity. The longevity of adult females that as larvae were treated with an LC₃₀ concentration of methoxyfenozide or thiodicarb was reduced by 28% and 23%, respectively, in comparison to control females. We predict that the combination of lethal and sublethal effects of the insecticides, especially methoxyfenozide, will induce significant effects on field population dynamics of H. armigera.     

Development of Temporal Model for Forecasting of Helicoverpa armigera (Noctuidae: Lepidopetra) Using Arima and Artificial Neural Networks

Helicoverpa armigera (Hübner) (Noctuidae: Lepidopetra) is a polyphagous pest of major crops grown in India. To prevent the damage caused by H. armigera farmers rely heavily on insecticides of diverse groups on a regular basis which is not a benign practice, environmentally and economically. To provide more efficient and accurate information on timely application of insecticides, this research was aimed to develop a forecast model to predict population dynamics of pod borer using Autoregressive Integrated Moving Average (ARIMA) and Artificial Neural Networks (ANN). The data used in this study were collected from the randomly installed sex pheromone traps at International Crops Research Institute for the Semi-arid Tropics (ICRISAT), Patancheru, Hyderabad. Several ARIMA (p, d, q) (P, D, Q) and ANN models were developed using the historical trap catch data. ARIMA model (1,0,1), (1,0,2) with minimal BIC, RMSE, MAPE, MAE, and MASE values and higher R² value (0.53) was selected as the best ARIMA fit model, and neural network (7-30-1) was found to be the best fit to predict the catches of male moths of pod borer from September 2021 to August 2023. A comparative analysis performed between the ARIMA and ANN, shows that the ANN based on feed forward neural networks is best suited for effective pest prediction. With the developed ARIMA model, it would be easier to predict H. armigera adult population dynamics round the year and timely intervention of control measures can be followed by appropriate decision-making schedule for insecticide application.     

Prevalence of Helicoverpa zea (Lepidoptera: Noctuidae) on late season volunteer corn in Mississippi: Implications on Bt resistance management

The southern United States has a long growing period between corn, Zea mays L., harvest and first winter frost, so volunteer corn which germinates after harvest has a growing period sufficient for corn earworm, Helicoverpa zea (Boddie) and fall armyworm, Spodoptera frugiperda (J. E. Smith) to feed on these plants. However, lower air temperatures can limit larval development on late season volunteer corn and thereby successful pupation. Here we explore the suitability of late season volunteer corn for larval development and the potential contribution of H. zea larvae to the overwintering population. Our survey revealed the occurrence of volunteer corn in high densities, with monthly mean densities ranging from 56,000 to 143,000 plants ha⁻¹. H. zea larvae were found feeding on both vegetative and reproductive stage plants while S. frugiperda were only found on vegetative stage plants. An analysis of H. zea growing degree day (GDD) accumulations based on Mississippi weather data from 1980 to 2010 revealed that sufficient GDD to reach prepupation would always be accumulated before first frost if oviposition occurred by 9 September, with the probability of successful pupation decreasing rapidly thereafter. However, most of the H. zea larvae were oviposited after this, and could not reach pupation. Because S. frugiperda cannot overwinter in Mississippi, their ability to pupate was not examined. Low suitability of whorl stage corn for H. zea development coupled with low larval densities during this stage effectively diminish the number of larvae that complete development on late season volunteer transgenic corn expressing genes from the soil bacterium, Bacillus thuringiensis (Bt). This limits the Bt resistance risk posed by larvae developing on late season volunteer corn in all but the most southern locations in the US.     

转BcWRKY1基因玉米对根际土壤酶活性及土壤理化性质的影响

采用盐碱土壤盆栽方法,以T7代转Bc WRKY1基因玉米株系WL-1、受体自交系LH1037、常规自交系K10为试材,分析其在不同生长时期对土壤酶活性和土壤理化性质的影响。结果表明,在播种后20、40、60、80 d对根际土壤进行检测,转Bc WRKY1基因玉米与受体亲本自交系和普通玉米自交系对照相比,土壤碱性磷酸酶的活性不存在差异显著性,个别取样点对土壤蔗糖酶、脱氢酶和脲酶活性存在显著差异;土壤电导率均无显著差异,在个别取样时期对土壤p H值和SAR值存在显著差异。这些显著性差异只在个别取样时期短暂存在,没有持续出现,且受体自交系与普通自交系不同品种间也具有显著差异,很难确定说明这些差异是由转基因玉米本身造成。     

Interference Efficiency and Effects of Bacterium-mediated RNAi in the Fall Armyworm (Lepidoptera: Noctuidae)

RNAi is an effective tool for gene function analysis and a promising strategy to provide environmentally friendly control approaches for pathogens and pests. Recent studies support the utility of bacterium-mediated RNAi as a cost-effective method for gene function study and a suitable externally applied delivery mechanism for pest control. Here, we developed a bacterium-mediated RNAi system in Spodoptera frugiperda based on four target genes, specifically, Chitinase (Sf-CHI), Chitin synthase B (Sf-CHSB), Sugar transporter SWEET1 (Sf-ST), and Hemolin (Sf-HEM). RNAi conducted by feeding larvae with bacteria expressing dsRNAs of target genes or injecting pupae and adults with bacterially synthesized dsRNA induced silencing of target genes and resulted in significant negative effects on growth and survival of S. frugiperda. However, RNAi efficiency and effects were variable among different target genes and dsRNA delivery methods. Injection of pupae with dsCHI and dsCHSB induced a significant increase in wing malformation in adults, suggesting that precise regulation of chitin digestion and synthesis is crucial during wing formation. Injection of female moths with dsHEM resulted in lower mating, fecundity, and egg hatching, signifying a critical role of Sf-HEM in the process of egg production and/or embryo development. Our collective results demonstrate that bacterium-mediated RNAi presents an alternative technique for gene function study in S. frugiperda and a potentially effective strategy for control of this pest, and that Sf-CHI, Sf-CHSB, Sf-ST, and Sf-HEM encoding genes can be potent targets.     

Insight Into the Ultrastructure of Antennal Sensilla of Mythimna separata (Lepidoptera: Noctuidae)

The oriental armyworm, Mythimna separata (Walk), is one of the most serious pests of cereals in Asia and Australasia. The structure and distribution of the antennal sensilla of M. separata were studied by scanning electron microscopy and transmission electron microscopy. The results showed that antennae of both female and male M. separata are filiform in shape. Three groups and seven morphological sensillum types were recorded in both sexes, including uniporous sensilla (sensilla chaetica), multiporous sensilla (sensilla trichodea, basiconica, coeloconica, and styloconica), and aporous sensilla (sensilla squamiformia and Böhm bristles). S. trichodea, which were the most abundant sensilla, was made of three subtypes (ST I, ST II, and ST III) according to external features and two subtypes of s. basiconica (SB I and SB II) and s. coeloconica (SCo I and SCo II) were identified, respectively. Sexual dimorphisms in sensilla of M. separata were mainly perceived as the variations in the numbers of several sensilla subtypes. Also, the possible functions of the antennal sensilla were discussed. These results contribute to our understanding of the function of antennae in the behavior of M. separata.     

Resistance of Spodoptera litura (Lepidoptera: Noctuidae) to profenofos: Relative fitness and cross resistance

Profenofos, an acetylcholine esterase inhibitor insecticide, has been used for the management of various lepidopteron pests of many crops in Pakistan. In the present study, we investigated the impact of insecticide resistance on fitness cost in Spodoptera litura, and evaluated cross resistance to other insecticides. The effect of profenofos on different life history parameters including survival rate, female ratio, fecundity and hatchability, intrinsic rate of population increase and biotic potential was determined. Significant differences associated with fitness costs were revealed. A field collected S. litura strain was selected by exposure to profenofos in the laboratory (Profen-SEL) and after 14 generations of selection it developed a 52-fold resistance to this insecticide. The Profen-SEL strain showed high cross-resistance to chlorpyrifos (62-fold), but very low to no cross resistance to lambda-cyhalothrin (2.34-fold) or methomyl (0.80-fold), respectively. The resistant strain had a relative fitness of 0.38 with a low larval survival rate, longer larval duration, longer male pupal duration, longer development time, low emergence rate of healthy adults, fecundity and hatchability compared with an unselected strain. The intrinsic rate of natural population increase, mean relative growth rate and biotic potential were lower for the selected strain compared with an unselected strain. Development of resistance may cause fitness costs for the resistant strain. This study provided important information for understanding profenofos resistance and facilitating a better strategy for the management of resistance.     

Selection,mechanism, cross resistance and stability of spinosad resistance in Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae)

Spodoptera litura is one of the most destructive pests in Pakistan and in many other regions of the world. A field collected population of S. litura was selected with spinosad for eleven generations under controlled laboratory conditions to study the cross resistance, mechanism and stability of spinosad resistance in S. litura. The resistance to spinosad in S. litura increased 3921-fold (after eleven generations of selection with spinosad) as compared to a susceptible population of S. litura. No cross resistance between spinosad and emamectin benzoate, methoxyfenozide, fipronil, indoxacarb, profenofos, lufenuron or deltamethrin was found in the spinosad-selected population of S. litura. To find the possible mechanism of spinosad resistance in S. litura two synergists, Piperonyl butoxide (PBO), S, S, S-tributyl phosphorotrithioate (DEF) were tested on the susceptible and resistant strains and on the un-selected field population. The values of the synergism ratios of PBO and DEF were 2.33 and 1.06 for the spinosad-selected strain, 1.36 and 1.06 for the un-selected field population and 1.14 and 1.00 for the susceptible strain, respectively. As high PBO ratio indicates the role of microsomal O-demethylase in causing spinosad resistance in S. litura. The spinosad-resistant and field populations of S. litura were reared without any selection pressure from the 12th to the 16th generation (G₁₂–G₁₆). The spinosad resistance decreased from 3921 to 678-fold in the spinosad-resistant population and from 31.1 to 15.1-fold in the un-selected population of S. litura as compared to the susceptible strain. Spinosad resistance in S. litura has a high reversion rate (−0.15) which indicates that spinosad resistance in S. litura is unstable and can be easily managed by switching off the selection pressure for a few generations or alternating with insecticides having different modes of action.     

Temperature Effects on the Development and Reproduction of Three Trichogramma (Hymenoptera: Trichogrammatidae) Species Reared on Trichoplusia ni (Lepidoptera: Noctuidae) Eggs

The cabbage looper, Trichoplusia ni (Hübner) (Lepidoptera: Noctuidae) is a generalist species and an important pest of Brassicaceae worldwide. Egg parasitoids are a feasible alternative for the control of this species. We evaluated the suitability of T. ni eggs as hosts for three Trichogramma Westwood (Hymenoptera: Trichogrammatidae) species and their tolerance to survive and develop within a range of temperatures between 15 and 30°C under laboratory conditions. The species evaluated were Trichogramma pretiosum Riley, Trichogramma atopovirilia Oatman and Platner, and Trichogramma acacioi Brun, Moraes and Soares. Parasitism rate was affected by temperature, parasitoid species, and by the interaction between these two factors. Parasitoids developed and reproduced in the range of temperatures evaluated, but Trichog. acacioi failed to parasitize T. ni eggs at 30°C. The highest parasitism rates of Trichog. atopovirilia and Trichog. pretiosum occurred at 20 and 25°C and Trichog. acacioi at 25°C, with parasitism rate above 70% in the three species. Parasitoid emergence was not affected by temperature or species. The estimated thermal constant and lower temperature threshold were 134.6 DD and 10.6°C for Trichog. pretiosum and 130.1 DD and 11.2°C for Trichog. atopovirilia. The results demonstrated that Trichog. pretiosum and Trichog. atopovirilia are the most suitable species for the control of T. ni, as they can remain active throughout the year in subtropical regions.     

斜纹夜蛾对植物挥发物及其与性信息素组合的触角电位反应

为了提高目前化学性诱剂的诱集效率,采用电生理方法测试斜纹夜蛾对4种植物气味化合物、4种植物叶片提取液及其与性诱剂混合组分的触角电位（Electroantennogram,EAG）反应。结果表明：这些植物挥发物均可刺激斜纹夜蛾产生触角电位反应,且随着浓度的增加,部分挥发物引起电位值呈逐渐上升趋势,剩余挥发物使电位值先上升后下降。试验所测单种植物挥发物对性诱剂均有显著的增效作用,而2种或2种以上气味化合物混合,只有苯乙醛和水杨酸甲酯同时存在时,对性诱剂才有增效作用,缺少其中任何1种,增效作用都不显著。此研究结果将为下一步开发研究斜纹夜蛾雄虫的引诱剂或性诱剂的增效剂提供重要的科学依据。     

Type II Collagen and Gelatin from Silvertip Shark (Carcharhinus albimarginatus) Cartilage: Isolation,Purification, Physicochemical and Antioxidant Properties

Type II acid soluble collagen (CIIA), pepsin soluble collagen (CIIP) and type II gelatin (GII) were isolated from silvertip shark (Carcharhinus albimarginatus) cartilage and examined for their physicochemical and antioxidant properties. GII had a higher hydroxyproline content (173 mg/g) than the collagens and cartilage. CIIA, CIIP and GII were composed of two identical α₁ and β chains and were characterized as type II. Amino acid analysis of CIIA, CIIP and GII indicated imino acid contents of 150, 156 and 153 amino acid residues per 1000 residues, respectively. Differing Fourier transform infrared (FTIR) spectra of CIIA, CIIP and GII were observed, which suggested that the isolation process affected the secondary structure and molecular order of collagen, particularly the triple-helical structure. The denaturation temperature of GII (32.5 °C) was higher than that of CIIA and CIIP. The antioxidant activity against 1,1-diphenyl-2-picrylhydrazyl radicals and the reducing power of CIIP was greater than that of CIIA and GII. SEM microstructure of the collagens depicted a porous, fibrillary and multi-layered structure. Accordingly, the physicochemical and antioxidant properties of type II collagens (CIIA, CIIP) and GII isolated from shark cartilage were found to be suitable for biomedical applications.     

Dry and Rainy Seasons Significantly Alter the Gut Microbiome Composition and Reveal a Key Enterococcus sp. (Lactobacillales: Enterococcaceae) Core Component in Spodoptera frugiperda (Lepidoptera: Noctuidae) Corn Strain From Northwestern Colombia

Spodoptera frugiperda is a polyphagous pest of several crops of economic importance. Nowadays, the insect is broadly distributed in America and, recently, in Africa, Asia, and Australia. The species has diverged into corn and rice strains. The role of the gut microbiota in insect physiology is relevant due to its participation in crucial functions. However, knowledge of seasonal variations that alter the gut microbiome in pests is limited. Gut microbiome composition between the dry and rainy seasons was analyzed with cultured and uncultured approaches in S. frugiperda corn strain larvae collected at Northwest Colombia, as seasonal microbiome changes might fluctuate due to environmental changes. On the basis of culture-dependent methods, results show well-defined microbiota with bacterial isolates belonging to Enterococcus, Klebsiella (Enterobacteriales: Enterobacteriaceae), Enterobacter (Enterobacterales: Enterobacteriaceae), and Bacillus (Bacillales: Bacillaceae) genera. The community composition displayed a low bacterial diversity across all samples. The core community detected with uncultured methods was composed of Enterococcus, Erysipelatoclostridium (Erysipelotrichales: Erysipelotrichaceae), Rasltonia (Burkholderiales: Burkholderiaceae), and Rhizobium (Hyphomicrobiales: Rhizobiaceae) genera, and Enterobacteriaceae family members. Significant differences in microbiome diversity were observed between the two seasons. The relative abundance of Erysipelatoclostridium was high in the dry season, while in the phylotype ZOR0006 (Erysipelotrichales: Erysipelotrichaceae) and Tyzzerella (Lachnospirales: Lachnospiraceae) genus, the relative abundance was high in the rainy season. The overall low gut bacterial diversity observed in the S. frugiperda corn strain suggests a strong presence of antagonist activity as a selection factor possibly arising from the host, the dominant bacterial types, or the material ingested. Targeting the stability and predominance of this core microbiome could be an additional alternative to pest control strategies, particularly in this moth.     

草地贪夜蛾对不同品种玉米室内危害级别及种群适合度比较

草地贪夜蛾[Spodoptera frugiperda(J.E.Smith)]是2019年由缅甸开始入侵我国的一种迁飞性农业害虫,具有取食范围广、极强的迁飞性、适应性及繁殖能力等特点.选育抗性品种是一项重要的农业防治手段,而评价不同玉米品种的危害级别对后续利用多组学分析筛选出特定的抗性基因,培育抗性品种具有指导作用.本...     

Insecticidal Activity and Insect Repellency of Four Species of Sea Lily (Comatulida: Comatulidae) From Taiwan

The methanol and ethyl acetate (EA) extracts of four species of sea lily (Himerometra magnipinna, Comaster multifidus, Comanthina sp., and Comatella maculata) were evaluated for their insecticidal activity against Yellow-fever mosquito larvae (Aedes aegypti) and their repellency against adult Asian Tiger mosquitoes (Aedes albopictus). The 24-hr minimum inhibition concentration (MIC) data revealed that the extracts from H. magnipinna and the C. maculata were the most active, killing mosquito larvae at 12.5 ppm. The toxicity of the extracts from these four sea lilies in descending order was H. magnipinna (12.5 ppm), C. maculata (12.5 ppm), C. multifidus (100 ppm), and Comanthina sp. (200 ppm). Furthermore, no significant difference in toxicity was found using either EA or methanol as the extraction solvent. The MIC at 12.5 ppm is promising as an insecticide lead. The repellency study results show that EA is a better solvent for one species (H. magnipinna), but the methanol is a better solvent overall. The repellency of these sea lily extracts in descending order was Comanthina sp. MeOH (ED₅₀ at 0.32%), followed by H. magnipinna EA (ED₅₀ at 0.38%), C. multifidus MeOH (ED₅₀ at 0.57%), C. maculata MeOH (ED₅₀ at 0.76%), C. multifidus EA (ED₅₀ at 1.25%), and H. magnipinna MeOH (ED₅₀ at 1.67%). A compound with ED₅₀ <0.5% is considered to be a promising repellant. Among the studied sea lilies, both Comanthina sp. and H. magnipinna have potential to be further developed as mosquito control agents due to their favorable toxicity and repellency.