Insecticidal potential of an endophytic fungus, Cladosporium uredinicola, against Spodoptera litura

The tobacco cutworm, Spodoptera litura (Lepidoptera: Noctuidae) (Fabricius), is a polyphagous pest which has developed physiological resistance against a number of known insecticides. In order to reduce the load of synthetic insecticides, ecofriendly alternative strategies are needed. The present studies were conducted to evaluate the insecticidal potential of the endophytic fungus Cladosporium uredinicola isolated from Tinospora cordifolia (Thunb.) on S. litura. Development of S. litura was significantly prolonged when larvae were fed on diet amended with ethyl acetate extract of C. uredinicola at concentrations of 1.25–2.00 μl?g^?1. The negative effects of fungal toxin on development of S. litura further resulted in a significant reduction in adult emergence, longevity and reproductive potential at higher concentrations. A significantly higher number of adults showed morphological deformities when larvae were fed on diet amended with 2.00 μl?g^?1 concentration. The inhibitory effects on growth and development of S. litura indicate toxicity of ethyl acetate extract of C. uredinicola, which is further evidenced by reduced food utilization by larvae. The antifeedant and toxic effects of ethyl acetate extract of C. uredinicola observed in the present studies can be attributed to a bioactive compound produced by the fungus, so this study provides evidence that C. uredinicola isolated from T. cordifolia possesses anti-insect properties and may play an important role in protecting plants against insect pests.     

Expression of δ-endotoxin Cry1EC from an inducible promoter confers insect protection in peanut (Arachis hypogaea L.) plants

BACKGROUND: Spodoptera litura (F.) is a polyphagous foliage insect and a major pest on peanut (Arachis hypogaea L.). Constitutive expression of δ‐endotoxin Cry1EC gives protection against S. litura, as reported earlier. In this study, insect bites and salicylic acid induced high‐level expression of Cry1EC was achieved in peanut. In order to achieve this, the expression of pathogenesis responsive promoter PR‐1a was enhanced by placing it downstream of the CaMV35S promoter in the pCAMBIA 1300 backbone. The resultant promoter CaMV35S(r)PR‐1a expressed a high level of insecticidal δ‐endotoxin Cry1EC. The Gus expression under the control of CaMV35S(r)PR‐1a served as a convenient marker for evaluation of promoter response to different treatments. RESULTS: Transgenic events that showed a very low level of uninduced expression and no expression in seeds were selected. The Cry1EC expression in leaves increased nearly eightfold in the selected event, following induction by salicylic acid. Both the salicylic‐acid‐treated and the S. litura‐bitten leaves showed the highest expression after 2 days. Leaves from salicylic‐acid‐induced transgenic plants caused 100% mortality of S. litura at all stages of larval development. CONCLUSION: The results suggest that high expression of inducible promoters provides a good strategy for the development of safer transgenic food and feed crops. Copyright © 2010 Society of Chemical Industry     

Design, synthesis and insecticidal activities of novel pyrazole amides containing hydrazone substructures

BACKGROUND: Pyrazole and hydrazone derivatives possess good insecticidal activities; their substructural units are widely used in pesticide design. In an effort to discover new molecules with good insecticidal activities, a series of pyrazole amide derivatives containing hydrazone substructures were synthesised and bioassayed. RESULTS: Bioassays demonstrated that some of the title compounds exhibited notable control of Plutella xylostella (Linnaeus), Helicoverpa armigera (Hübner), Culex pipiens pallens, Laphygma exigua (Hübner), Spodoptera litura (Fabricius), Nilaparvata lugens (Stål) and Rhopalosiphum maidis (Fitch) at 5, 10, 0.25, 200, 20, 100 and 500 mg L^?1 respectively. Comparative molecular field analysis (CoMFA) based on the bioactivities for P. xylostella was studied; the values of q² and r² for the CoMFA model were 0.701 and 0.964 respectively. CONCLUSION: Some of the title compounds displayed good and broad‐spectrum insecticidal activities against different insect species; the CoMFA model revealed that a bulky and negatively charged group at the 4‐position of benzene could enhance insecticidal activity. These results could provide useful information for the design of novel insecticide containing substructural units of pyrazole amide and hydrazone. Copyright © 2011 Society of Chemical Industry     

Fitness cost, cross resistance and realized heritability of resistance to imidacloprid in Spodoptera litura (Lepidoptera: Noctuidae)

Imidacloprid has been used as a key insecticide for controlling sucking insect pests of cotton, whereas Spodoptera litura also has been indirectly exposed to this insecticide in Pakistan. To evaluate the risk of resistance evolution and to develop a better resistance management strategy, a field collected population was selected with imidacloprid in the laboratory. Thereafter, fitness cost, realized heritability and cross resistance of imidacloprid resistance in S. litura were investigated. After 14 generations of selection with imidacloprid, S. litura developed a 137.48-fold resistance to the insecticide. Bioassay revealed that this strain showed cross-resistance to acetamiprid (RR 8.52) and a little to lamdacyhalothrin (1.92) but negative cross-resistance was found to methomyl (−0.19). The resistant strain had a relative fitness of 0.38, with substantially lower rates of larval survival, larval duration, male pupal duration, development time, emergence rate of healthy adults, fecundity, hatchability, and prolonged larval and pupal duration. Mean relative growth rate of the larvae, intrinsic rate of population increase, and biotic potential was lower for the selected populations. The estimated realized heritability (h²) of imidacloprid resistance was 0.15 in the resistant strain of S. litura. Development of the resistance may cost significant fitness for the resistant population. This study provided valuable information for further understanding the impact of imidacloprid resistance on physiological parameters of S. litura and for facilitating the development of resistance management strategies.     

Insecticidal activity of the pyrimidine nucleoside analogue (E)-5-(2-bromovinyl)-2'-deoxyuridine (BVDU)

The insecticidal activity of the antiherpetic agent (E)-5-(2-bromovinyl)-2'-deoxyuridine (BVDU) was assessed in in vivo assays against the fall armyworm, Spodoptera frugiperda (JE Smith) (Lepidoptera, Noctuidae). BVDU, mixed into an artificial diet, caused a variety of effects, depending on the concentration used. Compared with controls, food intake was lower, larval growth was retarded and larval development was prolonged. The treated larvae formed smaller pupae and the hatching moths often showed morphogenetic defects. A higher mortality could be found in larval and pupal stages and was generally caused by moult disruption. A choice assay showed that BVDU has very slight feeding-deterrent properties, which only partly explain the toxic effects. The agent most probably acts through its cytostatic activity that has been described previously using cell lines of different insect species.     

Insecticidal potential of Bowman-Birk proteinase inhibitors from red gram (Cajanus cajan) and black gram (Vigna mungo) against lepidopteran insect pests

The present study assessed the insecticidal potential of purified Bowman-Birk proteinase inhibitors from red gram (RgPI) and black gram (BgPI) towards lepidopteran insect pests. Both RgPI and BgPI showed remarkable inhibitory activity against midgut trypsin-like proteinases of Achaea janata. While, BgPI showed moderate to low inhibitory activity towards the midgut trypsin-like proteinases of Helicoverpa armigera, Spodoptera litura, Papilio demoleus, Amsacta albistriga, Corcyra cephalonica, Bombyx mori and Daphnis nerii, RgPI showed low to negligible inhibitory activity. The isoinhibitors of RgPI and BgPI were stable in presence of trypsin and chymotrypsin of bovine pancreatic origin, as well as larval midgut proteinases of A. janata, H. armigera and S. litura. The midgut trypsin-like proteinases of A. janata and H. armigera as well as midgut trypsin- and chymotrypsin-like proteinases of S. litura were susceptible to inhibition by RgPI and BgPI. Feeding assays displayed a dose-dependent decrease in body weight and survival rate of these larvae with increasing concentration of inhibitors supplemented in the diet. RgPI displayed significant reduction in body weight and survival rate of A. janata larvae compared with BgPI. Conversely, BgPI showed significant reduction in body weight of S. litura larvae compared with RgPI.     

新型杀虫剂甲磺虫腙的合成与杀虫活性

以对氯苯甲酰氯、苯甲醚、甲基磺酰氯、水合肼、丁酮等为原料合成了新型杀虫剂甲磺虫腙(试验号:ZJ0967),其化学名称为甲磺酸-4- 苯酯,其结构经1H NMR、MS和元素分析确认。室内生测结果表明,甲磺虫腙对小菜蛾Plutella xylostella、甜菜夜蛾Spodoptera exigua,特别是对粘虫Mythimna sepatara、斜纹夜蛾Prodenia litura表现出良好的杀虫活性。进一步毒力测定表明,甲磺虫腙对斜纹夜蛾的LC50值为8.45(7.69~9.62) mg/L,其杀虫活性与虫酰肼相当,但低于氟啶脲。田间试验结果表明,70%甲磺虫腙WG在有效成分为210~420 g/hm2时,对斜纹夜蛾7 d的防效可达88.6% ~93.9%,未观察到对作物产生药害。     

Antifeedant activity of a novel 6-(4,7-hydroxy-heptyl) quinone? from the leaves of the milkweed Pergularia daemia on the cotton bollworm Helicoverpa armigera (Hub.) and the tobacco armyworm Spodoptera litura (Fab.)

The effects of crude extracts and an isolated compound from the leaves of milkweed, Pergularia daemia (Forssk) Choiv., on the antifeedant activity against two important lepidopteran pests, Helicoverpa armigera (Hub.) and Spodoptera litura (F.), were studied. Maximum antifeedant activity was recorded in ethyl acetate crude extract against H. armigera (70.3%) and S. litura (71.82%) at 1% concentration. Ethyl acetate crude extract was further subjected to column chromatography, which was performed using hexane as initial solvent and then by increasing the polar strength using ethyl acetate. Fractions collected at hexane and ethyl acetate (80:20) yielded 6-(4,7-hydroxy-heptyl) quinone, a novel compound which showed significant antifeedant activity against H. armigera (80.22% at 2000 ppm) and S. litura (68.31% at 2000 ppm).     

斜纹夜蛾的生物控制研究

应用以作用因子组配的生命表技术及其相应的分析方法,开展了几项生物防治措施单项和联合使用防治斜纹夜蛾(Spodoptera litura Fabricius.)的试验。结果表明,施用斜纹夜蛾核型多角体病毒(Spodoptera litura nuclear polyhedrosis virus)(浓度为3.1×10~7PIBs/ml,即每g虫尸兑水800倍液)和散放叉角厉蝽(Cantheconidea furcellata Wolff)(1.8头/m~2)均能控制斜纹夜蛾种群的增长。采用两项生防措施后,种群趋势指数值分别降至对照的0.0259倍和0.0532倍,当联合使用这两项生防措施后,种群趋势指数值则降至对照的0.0109倍。浇施斯氏线虫需高剂量(40～80万条/m~2)才能控制斜纹夜蛾种群数量的增长,高剂量可使种群趋势指数值下降至对照的0.758～0.094倍。若以短期内对害虫的杀伤作用作为评价依据,散放叉角厉蝽(1.8头若虫/m~2)的效果最好,进入暴食期的虫口密度下降到对照的0.0917倍.     

Physiological effect of chitinase purified from Bacillus subtilis against the tobacco cutworm Spodoptera litura Fab.

An extracellular chitinase was purified from Bacillus subtilis. The lethal concentration (LC₅₀) was determined by using chitinase in first, second, and third instars of Spodoptera litura Fab. Chitinase showed the highest insecticidal activity at 6 μM concentration within 48 h. The nutritional indices were also significantly affected by the 6 μM concentration (P < 0.05). Food consumption, efficiency of conversion of ingested and digested food, relative growth rate, and consumption values declined significantly while approximate digestibility was increased. Our study indicates that treatment of host plant leaves with the chitinase can regulate (reduce) larval growth and weight, and enhance the mortality. This may serve as an effective biocide and alternative to Bt toxin.     

Insecticidal activity of crude seed extracts of<Emphasis Type="Italic">Annona</Emphasis> spp.,<Emphasis Type="Italic">Lansium domesticum</Emphasis> and<Emphasis Type="Italic">Sandoricum koetjape</Emphasis> against lepidopteran larvae

Crude ethanolic seed extracts ofAnnona muricata, A. squamosa (Annonaceae),Lansium domesticum andSandoricum koetjape (Meliaceae) collected from different locations and years in Maluku, Indonesia, were screened for inhibition of larval growth against the polyphagous lepidopteranSpodoptera litura (Noctuidae). Extracts ofA. squamosa were significantly more active (20-fold) than those ofA. muricata. A. squamosa collected from Namlea yielded the extracts with the greatest inhibitory activity. There were significant differences among locations for bothA. squamosa andA. muricata but not forL. domesticum andS. koetjape. Extracts ofA. squamosa, collected from Namlea, inhibited larval growth in a dose-dependent manner, with a dietary EC₅₀ (effective concentration to inhibit growth by 50% relative to controls) of 191.7 ppm fresh weight. Extracts ofA. squamosa collected from individual trees in Namlea also varied in growth inhibitory effect againstS. litura andTrichoplusia ni larvae. This species is a candidate for development of a botanical insecticide for local use in Indonesia. http://www.phytoparasitica.org posting Dec. 1, 2003.     

含单氟甲氧基的双酰胺类化合物的合成及杀虫活性

以2,3-二氯吡啶为起始原料,经肼基化、环合、氧化、取代、水解、环合和胺解反应,合成了15个文献未见报道的新型含单氟甲氧基的吡唑邻甲酰氨基苯甲酰胺类化合物,其结构通过核磁共振氢谱和高分辨质谱确认。初步的杀虫活性测试结果显示,所有目标化合物在100 mg/L下对粘虫Oriental armyworm的致死率均为100%,当测试浓度降低至4 mg/L时,化合物 8a 、 8d 、 8g 、 8k 和 8n 的致死率仍为100%,值得进一步研究。     

1,2-Diphenylaziridines as pesticides: Studies on acute toxicity and delayed effects

The insecticidal activities of 15 different 1,2-diphenylaziridines were evaluated. These compounds are readily obtained by photolysis of 1,2,3-triazolines; the latter can be conveniently prepared by the addition of diazomethane to Schiff bases in dioxane in the presence of water. Compounds containing a chloro, bromo or trifluoromethyl group in the para position of the 1-phenyl and a chloro in the ortho position of the 2-phenyl caused acute toxicity in 5th-instar Manduca sexta larvae via both oral and topical routes of exposure. Lower concentrations resulted in delayed effects such as reduced growth rate, pupal and adult malformations and reduced fecundity. When either phenyl group was unsubstituted, the activity was reduced. Unsubstituted 1,2-diphenylaziridine was inactive. Topical applications of l-(4-fluorophenyl)-2-(2-chlorophenyl) aziridine were active against representative species in the insect orders Lepidoptera, Coleoptera and Orthoptera.     

Effect of compost and casing treatments of insecticides against the sciarid Bradysia ocellaris (Diptera: Sciaridae) and on the total yield of cultivated mushrooms,Agaricus bisporus

BACKGROUND: Bradysia ocellaris (Comstock) is one of the major pests of cultivated mushrooms, Agaricus bisporus (Lange) Imbach. The feeding of sciarid fly larvae causes damage to the cultivation substrates, compost and casing. A comparative study of insecticidal treatments incorporated into compost and casing against B. ocellaris was conducted during 2003–2004. Treatments with an organophosphate, diazinon, a pyrazole, fipronil, and an insect growth regulator (IGR), triflumuron, were incorporated into casing. Another IGR, cyromazine, was incorporated into compost. Insecticidal incorporation into compost and casing has been associated with reductions in mushroom yield. Therefore, the effect of these insecticidal treatments on the overall yield was evaluated. RESULTS: A combined treatment, incorporation of cyromazine at 10 mg kg^?1 into compost and of triflumuron at 20 mg kg^?1 into casing, provided 100% control against B. ocellaris. There was no apparent reduction in yield as a result of incorporation of the tested chemicals into either compost or casing. CONCLUSION: The results obtained from this study suggest that incorporation of insecticides into both compost and casing is required to control a moderate to high pressure of insect pests. There were no significant yield reductions as a result of the incorporation of pesticides in the Australian mushroom‐growing system. Copyright © 2009 Society of Chemical Industry     

Effect of dihydrodillapiole on pyrethroid resistance associated esterase inhibition in an Indian population of Spodoptera litura (Fabricius)

Resistance in Spodoptera litura (Fabricius) has been attributed to enhanced detoxification of insecticides by increased levels of esterases, oxidases and/or glutathione S-transferases. Enzyme inhibiting insecticide synergists can be employed to counter increased levels of such enzymes in S. litura. Dihydrodillapiole induced synergism of pyrethroid toxicity was examined in the laboratory-reared third instar larval population of S. litura collected in Delhi (susceptible), and Guntur (resistant) region of Andhra Pradesh, India. The Guntur population was found to be 7.04 and 10.19 times resistant to cypermethrin and lambdacyhalothrin, respectively. The activity of cypermethrin, lambdacyhalothrin and profenophos against susceptible and resistance populations of S. litura, was gradually increased when used along with a plant-derived insecticide synergist dihydrodillapiole. The α-naphthyl acetate hydrolysable esterase activity in Delhi population was less as compared to the Guntur population. Resistance associated esterases in Delhi population were inhibited by pre-treatment with dihydrodillapiole. The esterase level in insect was instantly reduced initially, sustained for about 3 h and equilibrated at 4 h post treatment. The esterase activity of Guntur population was increased to 1.28 μmoles/mg/min at 2 h post treatment and subsequently reduced to lower than 0.70 μmoles at 4-12 h post treatment. The variation in esterase activity is suggestive of its homeostatic regulation in test populations. Dihydrodillapiole thus caused significant reduction of resistance in S. litura to cypermethrin, lambda cyhalothrin and profenophos.     

Cyt1Aa protein from Bacillus thuringiensis (Berliner) serovar israelensis is active against the Mediterranean fruit fly,Ceratitis capitata (Wiedemann)

BACKGROUND: Ceratitis capitata (Wiedemann) is one of the world's most destructive fruit pests. The aim of this study was to ascertain insecticidal activity of Bacillus thuringiensis (Berliner) δ‐endotoxins to C. capitata. RESULTS: Among 42 selected Bacillus strains, only B. thuringiensis serovar israelensis (Bti) solubilised protoxins showed biological activity against C. capitata neonate larvae, whereas Bti spore and crystal mixture was inactive. Insecticidal activity of Bti protoxins was significantly enhanced by incubation with Culex pipiens L. gut extracts. Overdigestion of Bti protoxins with Sesamia nonagrioides (Lefebvre) gut extracts suppressed biological activity against C. capitata, and this correlated with degradation of Cyt toxins. Cyt1Aa solubilised protoxin showed the highest toxicity, LC₅₀ after 7 days of 4.93 µg cm^?2, while proteolytical processing of Cyt1Aa protoxins by larval gut extracts did not enhance insecticidal activity. CONCLUSION: The present study provides evidence for the first time of the insecticidal activity of a B. thuringiensis strain against C. capitata and identifies a single δ‐endotoxin with potential for controlling this pest. Copyright © 2010 Society of Chemical Industry     

Mitochondrial impacts of insecticidal formate esters in insecticide‐resistant and insecticide‐susceptible Drosophila melanogaster

BACKGROUND: Previous research on insecticidal formate esters in flies and mosquitoes has documented toxicity profiles, metabolism characteristics and neurological impacts. The research presented here investigated mitochondrial impacts of insecticidal formate esters and their hydrolyzed metabolite formic acid in the model dipteran insect Drosophila melanogaster Meig. These studies compared two Drosophila strains: an insecticide‐susceptible strain (Canton‐S) and a strain resistant by cytochrome P450 overexpression (Hikone‐R). RESULTS: In initial studies investigating inhibition of mitochondrial cytochrome c oxidase, two proven insecticidal materials (hydramethylnon and sodium cyanide) caused significant inhibition. However, for insecticidal formate esters and formic acid, no significant inhibition was identified in either fly strain. Mitochondrial impacts of formate esters were then investigated further by tracking toxicant‐induced cytochrome c release from mitochondria into the cytoplasm, a biomarker of apoptosis and neurological dysfunction. Formic acid and three positive control treatments (rotenone, antimycin A and sodium cyanide) induced cytochrome c release, verifying that formic acid is capable of causing mitochondrial disruption. However, when comparing formate ester hydrolysis and cytochrome c release between Drosophila strains, formic acid liberation was only weakly correlated with cytochrome c release in the susceptible Canton‐S strain (r² = 0.70). The resistant Hikone‐R strain showed no correlation (r² < 0.0001) between formate ester hydrolysis and cytochrome c release. CONCLUSION: The findings of this study provide confirmation of mitochondrial impacts by insecticidal formate esters and suggest links between mitochondrial disruption, respiratory inhibition, apoptosis and formate‐ester‐induced neurotoxicity. Copyright © 2009 Society of Chemical Industry     

Laboratory evaluation of the insect growth regulator lufenuron againstHelicoverpa armigera on cotton

An insect growth regulator (IGR), lufenuron (Match 5EC), was tested for its toxicity toHelicoverpa armigera on cotton. Potency of the IGR against the larval stage of the pest was demonstrated with respect to larval instars; the LC₉₀ values of 1st, 2nd, 3rd, 4th and 5th instar larvae were 5.63, 7.89, 8.03, 11.39 and 14.76 mg a.i.l ⁻¹, respectively. However, different larval instars did not differ significantly with respect to LC₅₀ and LC₁₀. IGR-treated larvae had swollen heads and were significantly smaller (1.5–2.3 mm) than the untreated control (2.9 mm). Larval weight was significantly reduced from 190 mg in the control to 50–70 mg in the lufenuron treatment. IGR treatment in the larval stage significantly affected both pupal length and pupal weight. Pupal duration of the test insect was significantly extended by IGR treatment. Pupal deformities, including an inability to shed the last larval skin and formation of larval-pupal intermediates, occurred following treatment. A significant reduction in adult emergence was recorded. In addition, abnormalities in the form of development of cavities in the forewings of adult were evident. A significant decline in fecundity was noted in the studies. http://www.phytoparasitica.org posting Feb. 3, 2003.     

Dose-response relationships for the antifeedant effects of Humulus lupulus extracts against larvae and adults of the Colorado potato beetle

BACKGROUND: Dose–response relationships for antifeedant effects of H. lupulus extracts against larvae and adults of the Colorado potato beetle (CPB) were determined in laboratory conditions. The larval and adult beetles were fed on potato leaflets treated with H. lupulus extract ranging from 0.4 to 40 mg mL^?1 in a no‐choice situation. Their feeding behavior was recorded, and larval growth and antifeedant indexes were calculated. RESULTS: H. lupulus treatments significantly affected larval growth rate, and at higher concentrations the larval weights were significantly reduced over the course of the assay. Adults of CPB were more sensitive to the extracts than the larvae, and, even at lower doses, adult beetles were arrested for longer periods than larvae. CONCLUSION: These results indicate that H. lupulus extracts may have potential for control of CPB, particularly in organic farms where conventional insecticides are not available. Copyright © 2012 Society of Chemical Industry     

斜纹夜蛾核型多角体病毒对宿主实验种群增长的影响

在室内自然变温条件下,应用生命表方法评价了斜纹夜蛾核型多角体病毒对宿主实验种群增长的影响。结果表明,该病毒对斜纹夜蛾实验种群有明显的控制作用:①随着病毒接种浓度的升高,幼虫病死速率加快;②宿主感染病毒后,存活率、化蛹率降低,5、6龄幼虫历期明显延长,残存蛹羽化所得雌虫产卵量下降,当饲毒浓度达1.09×10~5PIBs/ml时,雌虫产卵量和产卵历期与对照差异显著(P<0.05),但病毒组各处理间无显著差异;③病毒能显著降低种群趋势指数(Ⅰ)值。各病毒组与对照的Ⅰ值差异极显著(P<0.01)。