Desensitization of fifth instar Spodoptera litura to azadirachtin and neem

The deterrence of azadirachtin, in its pure form and as a constituent of neem seed extract, to fifth instar Spodoptera litura (Fab.) larvae, was measured using cabbage, Brassica oleraceae (L.) var. capitata, leaf disc assays. Paired-choice assays, in which larvae could choose between feeding on a treated (1.3 ng azadirachtin per square cm leaf area) or an untreated leaf disc for 2 h, were conducted at 24 h intervals throughout the fifth instar. In addition, no-choice assays, in which larvae could feed on only one leaf disc (10 ng azadirachtin per square cm leaf area) for 1.5 h, were conducted consecutively over a six hour period at the beginning of the fifth instar. The effects of hunger and habituation on desensitization in our no-choice tests were partitioned. After repeated exposures, larvae became desensitized to pure azadirachtinal in both choice and no-choice tests, but did not desensitize to neem containing the same absolute amount of azadirachtin in choice tests. Hunger was responsible for approximately one third of the desensitization response in the no-choice tests. Sensitivity to azadirachtin was independent of age within the fifth instar.     

温度和食料对斜纹夜蛾种群的影响

用正弦模型Ｖ（Ｔ）＝Ａ＋Ｂｓｉｎ（Ｃ０＋Ｃ１ｅ＾Ｃ３Ｔ＋Ｃ２ｅ＾－Ｃ３Ｔ）拟合了斜纹夜蛾（Ｓｐｏｄｏｐｔｅｒａ ｌｉｔｕｒａ）发育与温度的关系,并用直接最优法估算了斜纹夜蛾不同发育阶段的温度阈值和所需热量。根据不同温度下的实验种群生命表资料,拟合了斜纹夜蛾不同发育阶段的存活率与温度关系的模型,卵、低龄幼虫、高龄幼虫、蛹的理论最适温度分别为２６．７、２４．７、２４．９、２５．８℃。本文研究了甘蓝、     

Interaction of Xestia c-nigrum granulovirus with peritrophic matrix and Spodoptera litura nucleopolyhedrovirus in Spodoptera litura

Xestia c-nigrum granulovirus (XcGV) was tested for its ability to increase Spodoptera litura nucleopolyhedrovirus (SINPV) infection in larvae of S. litura (F.). The interaction of XcGV with peritrophic matrix and SINPV in S. litura also was studied to account for the synergism. In dose-response bioassays with a constant XcGV concentration of 5-mg/ ml capsules and SINPV concentration that varied from 10(3) to 10(7) polyhedral inclusion bodies (PIB) per larva, XcGV increased the virulence of SINPV infection in fifth instars of S. litura. The lethal concentration of 50% individuals (LC50) of SINPV combined with XcGV was 3.35 x 10(5)PIB/ml, which was significantly lower than that of SINPV alone (2.17 x 10(6)). Compared with 10(7) PIB/ml SINPV alone, the lethal time of 50% individuals (LT50) of 10(7) PIB/ml SINPV combined with XcGV was not significantly shortened. In addition, no significant improvement in the activity and killing speed of SINPV progeny was noted after propagation with XcGV, indicating that native characters of SINPV associated with viral potency were not altered by XcGV. Investigation via environmental scanning electronic microscopy showed that the peritrophic matrix (PM) of S. litura exposed to XcGV or XcGV enhancin, or the combination treatment, was markedly disrupted. The outer surface of the PM was loose, or ruptured, which potentially facilitated the passage of virions through the PM. Therefore, it is reasonable to conclude that the synergy between XcGV and SINPV was closely associated with the disruption of the PM in S. litura.     

Biological activity of Pakistani isolate SpltNPV-Pak-BNG in second,third and fourth instar larvae of the leafworm Spodoptera litura

Recently, a novel isolate of the baculovirus Spodoptera litura nucleopolyhedrovirus (SpltNPV) has been isolated from Pakistan, which is distinct from the type species SpltNPV-G2 (ICTV). Here, we examined the biological activity of this isolate (SpltNPV-Pak-BNG) in second (L2), third (L3) and fourth instar (L4) larvae of the leafworm S. litura, more specifically to measure biological properties that are relevant for use of this virus for pest control under field conditions. The median lethal dose for L2 and L3 instar larvae was similar, but significantly lower than for L4 larvae. Likewise, the survival time was similar for L2 and L3 larvae (84?h), but was significantly longer for L4 instar larvae (108?h). Thus, in terms of efficacy, S. litura L2 and L3 instar larvae are the preferred targets for S. litura control with SpltNPV-Pak-BNG in field crops in Pakistan. On the basis of our data spray regimes can be designed to control the leafworm in cotton and vegetable crops targeting L2 and L3 larvae.     

Influence of post-treatment temperature, solvents and emulsifiers on the toxicity of cypermethrin to larvae of Spodoptera litura (Fab.)

Larvae of the tobacco caterpillar, Spodoptera litura (Fab.) were topically bioassayed with cypermethrin emulsion formulation and proprietary EC in combination with different solvents and emulsifiers for their toxicity at 16 ± 2°C and 27 ± 1°C. Among different solvents, the descending order of efficacy (with relative toxicity in parenthesis) against 9 ± 1 day old larvae of S. litura (Fab.) at 16 ± 2°C than 27 ± 1°C was: xylene (7.41), aromex (5.54), cyclohexane (4.93), C-IX (3.93), benzene (2.40) and toluene (2.26). With emulsifier, the order was: Triton X-100 (7.41), SN₄S (4.60), Teepol (2.90), Tween-80 (1.49), Swascofix DP-50 (1.28), SN₄R (1.10) and S₅₂B (1.07). However, the proprietary cypermethrin EC was 2.31 times more toxic at 16 ± 2°C than at 27 ± 1°C.     

Dynamics of Zea mays transcriptome in response to a polyphagous herbivore,Spodoptera litura

Functional & Integrative Genomics - Zea mays defense response is well-crafted according to the physical and chemical weapons utilized by their invaders during the coevolutionary period. Maize...     

Ascorbic acid, ascorbates and analogs in Spodoptera littoralis diet: Stability and effect on larvae

The dietary effect of L-ascorbic acid, its ascorbates and analogs at equimolar concentrations on larvae and pupae of the Egyptian Cotton Leafworm, Spodoptera littoralis (Boisd.) was studied. The daily activity loss of these compounds in the diet was determined with a 2,4 dinitrophenylhydrazine-thin layer chromatography method. This determination of ascorbates and analogs showed a rapid loss of activity down to about 50% after 4 days. However, ascorbic acid was significantly more stable. Storing ascorbic acid, its ascorbates and analogs at 6° only preserved their activity at 10–25% more than at 25°; sodium ascorbate, calcium ascorbate and L-dehydroascorbic acid equalled the activity of L-ascorbic acid in larval and pupal weight, as well as insect development. D-araboascorbic acid (=D-isoascorbic acid) did not support the normal insect development. Stability of ascorbic acid ascorbates and analogs in the diet in relation to their dietary effects is discussed.

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Résumé Ce travail étudie les effets sur les larves et les nymphes de Spodoptera littoralis (The Egyptian Cotton Leafworm), d'adjonction à l'alimentation d'acide L-ascorbique et de ses ascorbates et analogues à des concentrations équimoléculaires. Les pertes journalières d'activité de ces composés ont été déterminées par une méthode de chromatographie sur couches minces avec le 2–4 dinitrophenylhydrazine. Cette détermination des ascorbats et analogues a révélé une perte rapide d'activité jusqu'à environ 50% après 4 jours. Cependant l'acide ascorbíque est relativement plus stable. Le stockage à 6° de l'acide ascorbique, de ses ascorbates et analogues préservait leúr activité de seulement 10–25% de plus qu'à une température de 25°. L'ascorbate de sodium, l'ascorbate de calcium et l'acide L-dehydroascorbique montraient une activité égale à celle de l'acide L-ascorbique, quant à leur effet sur le poids des larves et pupes, aussi bien que sur le développement de l'insecte. L'acide D-ascorbique ne permet pas le développement normal de l'insecte. La stabilité de l'acide ascorbique, des ascorbates et des analogues dans l'aliment est discutée en rapport avec les effets observés.

     

Methyl jasmonate induced responses in four plant species and its effect on Spodoptera litura Fab. performance

Defensive proteins, such as polyphenol oxidase (PPO) and trypsin inhibitor (TI), are induced by herbivore wounding and exogenous methyl jasmonate application in various plant species. This study was conducted to measure induction of PPO and TI in radish, sweet pepper, tomato, and water spinach plants following herbivore wounding (I), methyl jasmonate application (M), and a combination of the two treatments (M + I). The effect of induced responses was also examined against third instar Spodoptera litura Fab. PPO activity was induced in radish by treatment I only; in sweet pepper, by treatments I and M; in tomato, by treatments I, M, and M + I; and in water spinach, by treatments M and M + I. The activity of TI was enhanced 1.2–1.4-fold in radish, sweet pepper, and tomato by M and M + I treatments, whereas in water spinach, it was enhanced 1.2-fold by all 3 treatments. The relative growth rate (RGR) of S. litura was reduced by 53% on radish plants following M treatment only. It was reduced by 37% and 42% on sweet paper plants following M and M + I treatment, respectively. RGR was significantly reduced on test tomato plants following I, M, and M + I treatments. The RGR of S. litura was unaffected on water spinach plants following any treatment. Collectively, the results of this study indicated that induction of plant defensive proteins in response to S. litura feeding or exogenous methyl jasmonate application varied among plant species, which further affected the induced plant resistance to the caterpillars.     

Pathogenicity of entomopathogenic fungi to eggs and larvae of Spodoptera litura,the common cutworm

The eggs and second instar larvae of Spodoptera litura were treated with different concentrations of conidial suspensions of six isolates of fungi belonging to five species, Metarhizium anisopliae var. anisopliae (Metschnikov) Sorokin (ARSEF 7487), Lecanicillium muscarium (Petch) Zare & W Gams (ARSEF 7037 and ARSEF 6118), Cordyceps cardinalis (ARSEF 7193), Fusarium lateritium Nees (ARSEF 8291/MTCC 9050) and Aspergillus sp. (ARSEF 8519). In bioassay with unscaled eggs, M. anisopliae, C. cardinalis, F. lateritium and Aspergillus sp. resulted in 100% mortality above 10⁶ conidia/mL. However, with scaled egg masses, the highest hatching rate (56%) was observed with L. muscarium (ARSEF 6118) whereas the lowest hatchings were observed in the case of M. anisopliae followed by L. muscarium (ARSEF 7037), Aspergillus sp., F. lateritium, and C. cardinalis. The larvae were also found susceptible to all isolates in a dose dependent manner. Three promising isolates against larvae, viz. M. anisopliae, F. lateritium and L. muscarium (ARSEF 7037) resulted in average percent mortalities of 88, 89 and 77%, respectively at ≈10⁸ conidia/mL. When both larvae and the leaves (provided as food) were treated with ≈10⁸ conidia/mL, mortality further increased for these isolates. Based on the mortality data and the LC₅₀ values, we suggest that M. anisopliae, F. lateritium and L. muscarium (ARSEF 7037) could be developed as potential biocontrol agents against rice cutworm in IPM programs.     

淡足侧沟茧蜂对甜菜夜蛾和斜纹夜蛾的寄生选择性研究

应用2因素2次回归正交旋转组合设计研究了淡足侧沟茧蜂Microplitis pallidipes对甜菜夜蛾Spodoptera exigua (Hubner)、斜纹夜蛾Spodoptera litura的寄生选择性,并建立了2种寄主共存时的被寄生模型.主效分析表明,甜菜夜蛾和斜纹夜蛾幼虫被寄生虫数均随寄主自身密度的增加而增加;淡足侧沟茧蜂对2种寄主无明显的选择性,对甜菜夜蛾、斜纹夜蛾幼虫共存时的选择寄生比率分别为0.5211、0.4788.在人工繁殖淡足侧沟茧蜂时,可以利用易于人工繁殖的斜纹夜蛾做为繁蜂寄主,提高淡足侧沟茧蜂的繁殖速度,降低繁蜂成本.在甜菜夜蛾、斜纹夜蛾发生期,可保护利用淡足侧沟茧蜂来控制蔬菜夜蛾.     

幼虫密度对斜纹夜蛾抗病能力的影响

为了阐明斜纹夜蛾Spodoptera litura Fabricius幼虫密度对其抗病能力的影响,在室内条件下(温度23℃±1℃,相对湿度75%)对不同幼虫密度(1、2、5、10、15头/皿(直径为12cm))饲养的斜纹夜蛾幼虫抵抗斜纹夜蛾核型多角体病毒侵染的能力及其免疫指标进行了研究。结果表明:幼虫密度对斜纹夜蛾幼虫接种核型多角体病毒后的存活率、存活时间及血淋巴酚氧化酶活性影响显著。随着幼虫密度的增加,接种核型多角体病毒后幼虫的存活率降低,存活时间缩短。当幼虫密度达到15头/皿时,幼虫存活率显著低于其它幼虫密度。不同幼虫密度幼虫的存活时间以1头/皿的最高,15头/皿的最低,且二者之间差异显著。幼虫血淋巴中酚氧化酶活性随幼虫密度的增加而明显降低,当幼虫密度达到5头/皿时,幼虫酚氧化酶活性显著低于1头/皿的。另外,幼虫溶菌酶活性和血细胞总数受幼虫密度影响不显著。不同密度幼虫抗病性的变化与其血淋巴中酚氧化酶活性的变化趋势较为一致。所以斜纹夜蛾幼虫抗病能力的降低可能与幼虫酚氧化酶活性的下降有关。因此,幼虫密度是影响斜纹夜蛾幼虫抗病性变化的重要因子。     

The effect of time to emergence on head weight and variation in head weight at maturity in lettuce (Lactuca sativa)

In lettuce, results of three experiments showed that between 60 and 90 % of the variation in mature head weight and the date of head maturity could be accounted for by variation in the date of seedling emergence. Sowing pre-germinated seeds using a fluid drill considerably reduced the time spread of both emergence and maturity compared with size-graded natural seed sown conventionally.     

The effect of pre-fasting diet and water temperature on liver glycogen and liver weight in rainbow trout, Salmo gairdneri Richardson, during fasting

The effect of feeding an isocaloric and isonitrogenous trout diet that contained different levels of digestible carbohydrate (cerelose) to rainbow trout at either 10 or 15° C on liver glycogen and liver weight was determined in two fasting studies of 12 and 41 days duration. Trout fed diets with increased levels of digestible carbohydrate (HC) had significantly higher liver-body weight ratios (LW) and liver glycogen (LG) than trout reared on low digestible carbohydrate diets (HF). Both LW and LG declined in fasting trout previously fed HC diets but declined little in fasting trout previously fed HF diets. Trout reared at 10° C had higher LW and LG than trout reared at 15° C on either the HC or HF diets. During fasting, the trout reared on HC diets at 10° C required a longer period of time for the LG and LW to decline to the levels of trout reared on the low carbohydrate diets, than did trout reared on the HC diets at 15° C. The results indicate that both pre-fasting diet and water temperature can affect liver glycogen utilization and liver weight in fasting trout. Prolonged elevation of LW and LG in fasting trout could jeopardize the survival rate of stocked trout, particularly at low water temperatures.     

寄主植物对斜纹夜蛾酯酶和乙酰胆碱酯酶活性的影响

利用生物测定与生物化学的方法,就取食不同寄主植物的2个斜纹夜蛾[Spodoptera litura(Fab.)]品系对丙溴磷和灭多威的敏感性及其体内的酯酶与乙酰胆碱酯酶的活性变化进行了研究。结果表明,取食不同寄主植物的斜纹夜蛾对丙溴磷和灭多威的敏感性不同。在敏感品系中,取食不同食料的斜纹夜蛾后代对灭多威的敏感性顺序为:烟草<棉花<大豆<人工饲料;对丙溴磷而言,敏感性顺序则为:棉花<烟草<大豆<人工饲料。而在田间抗性品系中,对丙溴磷的敏感性顺序为:棉花<烟草<人工饲料<大豆;对灭多威的敏感性顺序为:棉花<烟草<大豆<人工饲料。此外,在田间抗性和敏感品系中,取食不同食料的斜纹夜蛾体内的酯酶活性之间均存在显著差异,对其乙酰胆碱酯酶的活性也有程度不同的诱导效应,但并不会引起乙酰胆碱酯酶的质变。     

Cross-resistance and genetics of resistance to indoxacarb in Spodoptera litura (Lepidoptera: Noctuidae)

Bioassays (at generation G1) with a newly collected field population of Spodoptera litura (F.) (Lepidoptera: Noctuidae) from Multan, Pakistan, showed resistance ratios of 15, 23, 37, and 16 for indoxacarb, spinosad, abamectin, and emamectin, respectively, compared with a laboratory susceptible population, Lab-PK. At G1, the field population was selected with indoxacarb by using single pair crosses. For Indoxa-SEL, bioassay at G4 found that selection increased resistance ratio to 95 for indoxacarb compared with Lab-PK. Selection with indoxacarb significantly increased resistance to spinosad and emamectin; however, resistance to abamectin was observed to drop. A significant reduction in the resistance to indoxacarb was observed in Indoxa-SEL at G9, indicating unstable resistance to indoxacarb; however, it was stable for fipronil. Synergism tests with microsomal oxidase and esterase-specific inhibitors suggested that the indoxacarb resistance was associated with microsomal oxidase. Reciprocal genetic crosses between Indoxa-SEL and Lab-PK populations indicated that resistance was autosomal and incompletely dominant. Tests of monogenic inheritance suggested that resistance to indoxacarb was controlled by more than one locus.     

Avidin expressed in transgenic tobacco leaves confers resistance to two noctuid pests,Helicoverpa armigera and Spodoptera litura

Fertile transgenic tobacco plants with leaves expressing avidin in the vacuole have been produced and shown to halt growth and cause mortality in larvae of two noctuid lepidopterans, Helicoverpa armigera and Spodoptera litura. Late first instar H. armigera larvae and neonate (<12-h-old) S. litura larvae placed on leaves excised from T₀ tobacco expressing avidin at 3.1–4.6M (moles/kg of fresh leaf tissue) had very poor growth over their first 8 days on the leaves, significant numbers had died by days 11 or 12 and all were dead by day 22 (H. armigera) or day 25 (S. litura). Similar results were obtained when late first instar H. armigera larvae were placed on leaves from T₁ plants expressing avidin at six different average concentrations, ranging from 3.7 to 17.3M. Two larvae on the lowest expressing leaves survived to pupation, but there was total mortality among the other groups and no relationship between avidin concentration and the effects on the larvae. Synergistic effects between avidin-expressing tobacco plants and a purified Bt toxin, Cry1Ba, were demonstrated. Late instar H. armigera larvae fed with leaves from T₂ plants expressing avidin at average concentrations of either <5.3 or >12.9M, and painted with Cry1Ba protein at a rate equivalent to an expression level of 0.5% of total leaf protein, died significantly faster than larvae given either of the two treatments alone. Larvae fed with avidin-expressing leaves painted with the protease inhibitor, aprotinin, at a rate equivalent to 1% of total leaf protein had mortality similar to those given avidin-leaves alone. There was no evidence of antagonism between these two proteins.     

Effects of sublethal dose of chlorfluazuron on testicular development and spermatogenesis in the common cutworm, Spodoptera litura

This paper describes the physiological mechanism of action of chlorfluazuron on testicular development and spermatogenesis when sublethal doses (LD₁₀: 1.00 ng/larva or LD₃₀: 3.75 ng/larva) are applied topically to the cuticle of newly moulted fifth instars of the common cutworm Spodoptera litura (F.) (Lepidoptera, Noctuidae). These doses disrupt the growth and development of testes by decreasing the volume and weight of testes and thickness of testes sheath as compared with that of the controls. Sublethal doses of chlorfluazuron also significantly reduce the protein content of the testis, but do not affect the carbohydrate and lipid contents in newly emerged treated males when measured in μg/mg of testis as compared with that of the controls. Additionally, such doses disrupt spermatogenesis by reducing the number and size of eupyrene and apyrene sperm bundles in the testis. Very few or no eupyrene sperm bundles are observed in vas deferens of pre‐ and newly moulted adults compared with controls. This result shows that the transfer of sperm bundles from testes to vas deferens is delayed in treated males. The effects of chlorfluazuron on testicular development and spermatogenesis is thought to be one of the factors responsible for the reduction in fecundity, fertility and hatchability caused by sublethal doses of chlorfluazuron.     

Resistance to selected organochlorin, organophosphate, carbamate and pyrethroid, in Spodoptera litura (Lepidoptera: Noctuidae) from Pakistan

The toxicity of the most commonly used insecticides of organochlorine, organophosphate, pyrethroid, and carbamate groups were investigated against Spodoptera litura (F.) (Lepidoptera: Noctuidae) populations collected for three consecutive years (2004-2006). For a chlorocyclodiene and pyrethroids tested, the resistance ratios compared with Lab-PK were in the range of 10- to 92-fold for endosulfan, 5- to 111-fold for cypermethrin, 2- to 98-fold for deltamethrin, and 7- to 86-fold for beta-cyfluthrin. For organophosphates and carbamates, resistance ratios were in the range of 3- to 169-fold for profenofos, 18- to 421-fold for chlorpyrifos, 3- to 160-fold for quinalphos, 6- to 126-fold for phoxim, 7- to 463-fold for triazophos, and 10- to 389-fold for methomyl and 16- to 200-fold for thiodicarb. Resistance ratios were generally low to medium for deltamethrin and beta-cyfluthrin and high to very high for endosulfan, cypermethrin, profenofos, chlorpyrifos, quinalphos, phoxim, triazophos, methomyl, or thiodicarb. Pairwise comparisons of the log LC50 values of insecticides tested for all the populations showed correlations among several insecticides, suggesting a cross-resistance mechanism. Integration of timely judgment of pest problem, delimiting growing of alternate crops such as arum, rotation of insecticides with new chemicals, and insect growth regulators in relation to integrated pest management could help in manageable control of this important pest.