Induction of microsomal oxidases by host plants in the fall armyworm,Spodoptera frugiperda (J. E. Smith)

Larvae of the fall armyworm (Spodoptera frugiperda (J. E. Smith)) were maintained on a semidefined artificial diet until the end of the fifth instar and the newly molted sixth-instar larvae were then fed fresh leaves of various host plants for 2 days prior to microsomal oxidase assays. The order of the midgut aldrin epoxidase activity of larvae after feeding on these plants was: corn > Bermuda grass > cotton > cowpeas > cabbage > peanuts > sorghum > alfalfa > millet > soybean. The ratios of aldrin epoxidase, p-nitroanisole O-demethylase, and p-chloro-N-methylaniline N-demethylase activities for soybean- and corn-fed larvae were 4.5, 6.3, and 2.7-fold, respectively. The induction was affected by the age and developmental stage of the corn plant with mature leaves from old plants being more active. Higher epoxidase activities were also observed in mature larvae reared on corn plants since egg stage as compared with those on soybean plants. Monoterpenes such as α-pinene, β-pinene, limonene, menthol, and peppermint oil were found to induce the midgut epoxidase activity. Corn-fed larvae were more tolerant of the insecticides methomyl, acephate, methamidophos, diazinon, trichlorfon, monocrotophos, permethrin, and cypermethrin than soybean-fed larvae.     

Induction of detoxifying enzymes by allelochemicals and host plants in the fall armyworm

The effect of various plant substances and host plants on the microsomal oxidases and glutathione S-transferase was investigated in the fall armyworm (Spodoptera frugiperda (J. E. Smith)) maintained on a meridic diet. The glucosinolate, sinigrin, and the hydrolytic products of glucosinolates, β-phenylethylisothiocyanate, indole 3-acetonitrile, and indole 3-carbinol, and flavone were found to be potent inducers of the glutathione S-transferase in the armyworm. An 18-fold increase in the transferase activity was observed when larvae were fed a diet containing 0.2% indole 3-acetonitrile for 2 days. These compounds, with the exception of β-phenylethylisothiocyanate which appeared to be inhibitory, also stimulated the microsomal aldrin epoxidase significantly. In all instances, no induction of the microsomal oxidase or glutathione S-transferase was observed by the plant hormones, indole 3-acetic acid and gibberellic acid; the terpenoids, stigmasterol, sitosterol, and β-carotene; the polyphenolic gossypol; and the flavonol, quercetin; some of them were found to be inhibitory. Using corn, potato, and sweet potato as inducers of various microsomal oxidases, it was found that the inducing pattern of the N-demethylase was different from the two epoxidases and O-demethylase. Corn leaves were the most active compared with other aerial parts of corn (silks, developing corn, and husk) in inducing the microsomal oxidase. The microsomal oxidase in the younger larvae appeared to be less inducible by host plants than in the older larvae.     

Interactions of allelochemicals with detoxication enzymes of insecticide-susceptible and resistant fall armyworms

The induction of glutathione S-transferases and microsomal oxidases by host plants and allelochemicals was examined in sixth-instar larvae of insecticide-susceptible and resistant strains of the fall armyworm, Spodoptera frugiperda (J. E. Smith). Among 11 host plants studied, parsnip and parsley were the best inducers of glutathione S-transferase, resulting in increases of 39- and 19-fold, respectively, compared with the artificial diet. The inducer in parsnip leaves was identified by mass spectrometry, high-pressure liquid chromatography, gas chromatography, and thin-layer chromatography as xanthotoxin, a furanocoumarin. Xanthotoxin also showed a bimodal effect on the microsomal oxidase systems, increasing cytochrome P-450 content and heptachlor epoxidase activity but inhibiting aldrin epoxidase, biphenyl 4-hydroxylase, and p-chloro-N-methylaniline N-demethylase. Using indole 3-acetonitrile, indole 3-carbinol, and flavone as inducers, the inducing pattern of glutathione S-transferases was the same toward 3,4-dichloronitrobenzene, 1-chloro-2,4-dinitrobenzene, and methyl iodide. Microsomal oxidase and glutathione S-transferase were also inducible by host plants and allelochemicals in larvae of a carbaryl-resistant strain.     

Induction of glutathione S-transterase by fumigants in larvae of the Khapra beetle,Trogoderma granarium (E.)

The effect of fumigants on glutathione and glutathione S-transferase in the Khapra beetle larvae (Trogoderma granarium) was studied by fumigating for 1, 3, and 5 hr with a dose causing 100% mortality at 24 hr of exposure. Glutathione and glutathione S-transferase were assayed in the cytosol at 1, 3, and 5 hr of exposure. Time-dependent depletion of glutathione was seen for all fumigants except carbon tetrachloride and phosphine. The depletion was maximum (60–70%) in the cases of methyl bromide, methyl iodide, and acrylonitrile, and least (20–30%) in the cases of ethylene dibromide and ethylene oxide. The order of glutathione depletion by various fumigants at 5 hr exposure was methyl iodide > methyl bromide = acrylonitrile > ethylene dichloride > ethylene oxide > ethylene dibromide. Glutathione S-transferase was induced by all fumigants except ethylene dibromide, methyl bromide being more potent than methyl iodide. The enzyme induction ranged from 186% by acrylonitrile to 40% by carbon tetrachloride. Mortality above 10% correlated well with the degree of GSH depletion (r = 0.729) whereas the latter did not correlate with the transferase induction.     

Studies on the mechanisms responsible for variable toxicity of azinphosmethyl to various larval instars of the tufted apple budmoth, Platynota idaeusalis

The susceptibility of tufted apple budmoth larvae, Platynota idaeusalis, to azinphosmethyl decreases with each successive instar. A comparison between fifth and third instars showed that the fifth instars have a higher level of glutathione S-transferase activity per milligram of protein, a lower content of cytochrome P-450 per milligram of protein, and absorb a lesser percentage of and LD₀₁ dose than the third instar. Results of metabolism were consistent with these findings. In addition to these factors, the fifth instar larvae may have a threshold mechanism for eliminating penetrated azinphosmethyl from the body, unchanged. This allows the fifth instar larval population to withstand increasingly higher doses of azinphosmethyl without a proportional increase in mortality.     

寄主植物对甜菜夜蛾生长发育和消化酶活性的影响

通过室内饲养和生化测定,研究了甜菜、玉米和黄瓜3种寄主植物的营养物质及其对甜菜夜蛾幼虫发育、成虫产卵及5龄幼虫体内蛋白质和总氨基酸含量、淀粉酶和脂肪酶活力的影响.结果表明:与取食玉米和黄瓜的个体相比,取食甜菜的甜菜夜蛾,其幼虫期和蛹期较短,分别为11.4天和5.6天;蛹期存活率最高,达100%;成虫寿命较长,为26.3天;单雌产卵量最高,为301.8粒.取食3种寄主植物,甜菜夜蛾5龄幼虫体内的蛋白质含量无差异,但总氨基酸含量差异显著,此外,幼虫体内淀粉酶和脂肪酶活力也存在显著差异,取食甜菜的个体>取食玉米的个体>取食黄瓜的个体.取食不同寄主植物,甜菜夜蛾幼虫的消化酶和脂肪酶活力与其发育适合度呈正相关.     

Induction of detoxification enzymes by triazine herbicides in the fall armyworm, Spodoptera frugiperda (J.E. Smith)

The inductive effect of six triazine herbicides on a variety of detoxification enzymes was investigated in fall armyworm (Spodoptera frugiperda) larvae maintained on an artificial diet. Dietary atrazine induced nine microsomal oxidase activities ranging from 1.3- to 21.6-fold, 12 glutathione S-transferase activities ranging from 1.3- to 4.2-fold, four hydrolase activities ranging from 1.3- to 2.9-fold, and two reductase activities ranging from 1.5- to 5.1-fold, depending on the enzyme assayed and tissue source (midgut vs. fat body) used. Simazine, cyanazine, ametryn, tebutryn, and terbuthylazine also induced these detoxification enzymes. The induction of microsomal oxidase (aldrin epoxidase) ranged from 1.2- to 11-fold, glutathione S-transferase (CDNB) ranged from 1.3- to 4-fold, and general esterase ranged from 1.4- to 4.1-fold, depending on the tissue source examined. In general, fat bodies were more inducible than midguts with respect to these detoxification enzymes, especially the microsomal oxidases. The induction by atrazine was associated with decreased toxicity of carbaryl, permethrin and indoxacarb, but increased toxicity of methyl parathion, phorate, and trichlorfon.     

Glutathione S-transferase in the Australian sheep blowfly,Lucilia cuprina (Wiedemann)

Glutathione S-transferase in the Australian sheep blowfly, Lucilia cuprina, was studied using 3,4-dichloronitrobenzene (DCNB) and 1-chloro-2,4-dinitrobenzene (CDNB) as substrates. The optimum pHs for enzyme activity were 7.5–8.0 and 6.7–7.4 for DCNB and CDNB conjugations, respectively. Inclusion of glutathione and bovine serum albumin in the homogenizing buffer protected the glutathione S-transferase from inhibition by endogenous compounds present in extracts of final instar larvae and of adults less than 7–8 days old. Conjugation activities for DCNB and CDNB increased throughout larval development to reach a peak early in the pupal stage. Activity then decreased through the remainder of the pupal stage and for the first 6–7 days after emergence of the adult. Almost all of the decrease in activity during the first 6 days of the adult occurred in the abdomen, which accounted for 85% of total activity in the adult female at emergence but only 47% at 6 days. Larval DCNB conjugation activity was localized almost entirely in the fat body (94%), whereas only 50% of the CDNB conjugation activity was in the fat body with the remainder in the cuticle (25%), gut (15%), and blood (10%). Adult and larval enzyme was induced ca. three- to four-fold by sodium phenobarbital. The induction was associated with changes in apparent V_max rather than apparent K_m, suggesting that phenobarbital caused increased production of forms of enzymes already present rather than inducing synthesis of altered or new forms.     

寄主植物对棉铃虫生理代谢的影响

作者研究了取食不同寄主植物的棉铃虫(Heliothis armigera Hübner)在生长发育和生理代谢上的变化。结果表明:(1)取食不同寄主植物的幼虫发育天数差异较大,其顺序是:棉铃(14天)=人工饲料(14天)<扁豆(16天)<番茄(19天)<青椒(23天);(2)所有供试害虫均含有17种游离氨基酸,谷氨酸、甘氨酸和精氨酸是主要组成成份,第3龄期的差异比较显著;(3)多功能氧化酶和羧酸酯酶的活力随幼虫发育逐渐减小。3龄时期幼虫的活力较高于其他时期,取食青椒的棉铃虫酶活力高于其他4种植物。上述结果说明,幼虫第3龄期可能是解毒的关键时期,代谢过程是多酶系的复合反应,酶活力的变化与棉铃虫的生长发育不成正比,多功能氧化酶是重要的解毒酶,羧酸酯酶作为水解酶起到一定的辅助作用。     

The effect of phenobarbital induction on glutathione conjugation of diazinon in susceptible and resistant house flies

The relationship between glutathione S-transferase activity toward 3,4-dichloronitrobenzene and O-alkyl or O-aryl conjugation of diazinon was investigated in eight strains of house flies. No significant difference was found in the amount of O-aryl conjugation. In contrast, house flies which had higher glutathione S-transferase activity toward 3,4-dichloronitrobenzene also had higher O-alkyl conjugating activity toward diazinon. The glutathione S-transferase(s) in phenobarbital-pretreated flies degraded diazinon faster than those in the nontreated ones. The present results showed that the formation of the O-alkyl conjugate was enhanced by phenobarbital pretreatment, while the formation of the O-aryl conjugate was not affected by induction. Based on these findings, it would appear that one of the multiple forms of glutathione S-transferase is specifically induced and responsible for the increase in O-alkyl conjugation.     

Endogenous inhibitors of glutathione S-transferases in house flies

The inhibition of glutathione S-transferase by endogenous compounds present in the soluble fraction of house fly homogenates was investigated. The highest inhibition was found with the female abdomen and increased with incubation time and with an increase in the tissue concentration. The correlation of increased inhibition with a parallel increase in the darkening of the soluble fraction indicated a possible association with melanization, thereby suggesting quinones as the possible endogenous inhibitiors of glutathione transferase. In vitro experiments demonstrated that quinones produced by mushroom tyrosinase did indeed inhibit glutathione S-transferase. Inhibition by quinones can be prevented by including glutathione or bovine serum albumin in the homogenization buffer. The inhibitory activity of a variety of quinones and related compounds on purified glutathione S-transferase was investigated. Oxygenated aromatics with hydroxy groups in the 1,2- or 1,4-position or ketonic carbonyls in the 1,4-position are good inhibitors of glutathione S-transferase.     

Influence of three diets on susceptibility of selected insecticides and activities of detoxification esterases of Helicoverpa assulta (Lepidoptera: Noctuidae)

The oriental tobacco worm, Helicoverpa assulta Guenée, is one of the most destructive pests of tobacco and peppers in China. We determined the susceptibility of H. assulta reared on an artificial diet, chili pepper and tobacco to four insecticides (fenvalerate, phoxim, methomyl, indoxacarb) under laboratory conditions associated with the activities of acetylcholinesterase (AChE), carboxylesterase (CarE) and glutathione S-transferase (GST) in its larvae. H. assulta larvae that were fed with chili pepper were more susceptible to fenvalerate, indoxacarb, and phoxim than those that were fed with tobacco and the artificial diet, but not to methomyl. The larvae that were fed with chili pepper were 3.65-, 2.49-, 1.92- and 2.44-fold more susceptible to fenvalerate, phoxim, methomyl, and indoxacarb than those fed with tobacco, respectively. The AChE activities of H. assulta larvae that were fed with chili pepper and tobacco were 2.12 and 1.07 μmol mg⁻¹ 15 min⁻¹, respectively, almost 2-fold difference. The CarE activity of H. assulta larvae that were fed with chili pepper, tobacco and the artificial diet was 4.12, 7.40 and 7.12 μmol mg⁻¹ 30 min⁻¹, respectively. Similarly, the GST activities of H. assulta larvae that were fed with chili pepper, tobacco and the artificial diet was 52.02, 79.37 and 80.02 μmol mg⁻¹ min⁻¹, respectively. H. assulta larvae that were fed with chili pepper were more resistance to the tested insecticides. The low activities of AChE and the high activities of CarE and GST lead to H. assulta become more susceptible to the tested insecticides.     

Toxicokinetics of Malathion in Larval Stages of the Toad Bufo arenarum (Hensel): Effect of Exogenous Spermidine

The aim of this work was to study the absorption, biotransformation, and excretion of malathion (¹⁴C-methoxy) and its metabolites in larval stages of the toad Bufo arenarum (Hensel). Also, changes in malathion metabolization by the action of the exogenous polyamine spermidine were studied. Malathion clearance from the media was uniexponential, and spermidine reduced the uptake in the larvae, causing an increase in the apparent half-life of the toxicant. Concomitant with this effect, spermidine increased the level of induction of mixed-function oxidases due to malathion and caused a progressively higher malaoxon/malathion ratio. As a consequence of the higher conversion to the active metabolite malaoxon, spermidine also provoked a significant enhancement in the inhibitory effect of Malathion on acetylcholinesterase activity. [methoxy¹⁴C]malathion metabolites, such as carboxylesterase and glutathione S-transferase products, were detected in the toad larvae and in the media. The excreted products of carboxylesterase activity were about 70% of the total radioactivity, and the glutathione S-transferase products (methyl glutathione) were 20–30% of the total radioactivity. No significant variations in the levels of excreted products due to the action of exogenous spermidine were detected. Malathion inhibited carboxylesterase activity, independent of the presence of spermidine in the media. In turn, glutathione S-transferase activity was induced by spermidine, but was not affected by the exposure to low concentrations of malathion for 48 h. We conclude that the presence of spermidine in the medium modifies malathion toxicokinetics, increasing its toxicity in B. arenarum larvae.     

Effect of celangulin V on detoxification enzymes in Mythimna separata and Agrotis ypsilon

Celangulin V (CA-V), a β-dihydroagrofuran sesquiterpene polyol ester, is extracted from the root bark of Chinese bittersweet, Celastrus augulatus Maxim. It exhibited selective toxicity against different insects. By CO-difference spectral and biochemical method, the effects of CA-V on two kinds of detoxification enzymes, cytochrome P450 (P450 and NADPH-cytochrome P450 reductase) and glutathione S-transferase, were investigated in oriental armyworm, Mythimna separata and black cutworm, Agrotis ypsilon. CA-V showed higher induction against P450 of M. separata than that of A. ypsilon. Treated by CA-V, the maximum absorption of M. separata increased 1.2 and 0.8 nm than the control, respectively. Meanwhile, compared with the control, the P450 content and NADPH-P450 reductase activity in treated M. separata larvae increased 1.46-, 2.26- and 1.26-, 2.56-fold, respectively. But in treated A. ypsilon larvae, they all increased a little more than those of control. So far as M. separata and A. ypsilon, whether there is exposure of CA-V or not, the P450 content and GST activity in A. ypsilon were obviously higher than those in M. separata. It suggested that the content or activity difference of these two kinds of detoxification enzymes may have important roles in the selective toxicity of CA-V in M. separata and A. ypsilon.     

Host plant stimulation of detoxifying enzymes in a phytophagous insect

The midgut microsomal aldrin epoxidase of variegated cutworm larvae (Peridroma saucia, Hübner) fed bean or peppermint leaves was up to 10 and 45 times more active, respectively, than that of larvae fed a basic control diet. Large increases in oxidase activity and cytochrome P-450 levels also occurred in larvae fed mint plant constituents such as menthol menthone, α-pinene, and β-pinene. Mint-fed larvae were more tolerant of the insecticide, carbaryl, than bean-fed larvae.     

The phenylurea cytokinin 4PU-30 protects maize plants against glyphosate action

The effects of the phenylurea cytokinin 4PU-30 and the herbicide glyphosate, applied alone and in combination on young maize plants were investigated. The influence of the compounds on the changes of growth, chlorophyll content, levels of hydrogen peroxide, and some stress markers, the activities of peroxidase, catalase, and glutathione-S-transferase, as well as glutathione amount were measured 3, 6, and 10 days after the treatment. The application of glyphosate increased the levels of lipid peroxidation, glutathione, and free proline content, ion fluxes, and the activity of catalase, guaiacol peroxidase, and glutathione-S-transferase, i.e., along with the inhibition of its target enzyme the herbicide induced also an oxidative stress. We found that the phenylurea cytokinin 4PU-30 alleviated in some extent the detrimental effects due to the glyphosate action. Moreover, we speculated that the cytokinin renders its protective action by induction of “hardiness” in the antioxidant defense systems in maize plants similarly to the effects observed after the application of some herbicide safeners.     

The biochemistry of insecticide resistance in Anopheles sacharovi: Comparative studies with a range of insecticide susceptible and resistant Anopheles and Culex species

Fourth instar larvae, the progeny from wild-caught Anopheles sacharovi females, were subjected to a number of biochemical tests and the results were compared to those from similar tests on laboratory insecticide resistant and susceptible strains of anopheline and culicine mosquitoes. DDT resistance in An. sacharovi is associated with the ability to rapidly metabolise DDT to DDE. The organophosphorus and carbamate resistance was not associated with quantitative changes in esterases, multifunction oxidases, or glutathione S-transferase. The acetylcholinesterase was less sensitive to malaoxon and propoxur than laboratory susceptible An. albimanus, and plots of inhibition suggest that the population was polymorphic for more than one form of acetylcholinesterase. Metabolism studies on malathion and pirimiphos methyl did not indicate resistance due to increased metabolism. There was no evidence of penetration barriers contributing to resistance to either DDT or malathion, and there was no indication of any resistance to pirimiphos methyl in our tests.     

亚致死浓度氯虫苯甲酰胺对小菜蛾药剂敏感度和解毒酶活性的影响

采用叶片药膜法,使用亚致死浓度(LC10、LC25)的氯虫苯甲酰胺对小菜蛾Plutella xylostella(L.)3龄幼虫连续处理5代后,试虫对氯虫苯甲酰胺的敏感度分别比敏感品系下降了57.3% 和67.7%,同时对多杀菌素的敏感度也分别下降了60.2% 和51.5%,但对毒死蜱和高效氯氰菊酯的敏感度变化不明显。采用该浓度的氯虫苯甲酰胺分别处理小菜蛾3龄幼虫24、48和72 h,可诱导其羧酸酯酶(CarE)比活力上升,但对细胞色素P450 O-脱乙基酶(ECOD)、谷胱甘肽S-转移酶(GSTs)和芳基酰胺酶(AA)有明显的抑制作用;连续处理5代后,小菜蛾CarE和ECOD的比活力显著高于对照组,分别为对照组的1.16、1.40倍和1.65、1.56倍,但GSTs和AA的比活力则分别比对照下降了11.0%、27.5%和43.6%、52.5%。结果表明,小菜蛾对氯虫苯甲酰胺产生抗性的风险较高;羧酸酯酶和多功能氧化酶可能与小菜蛾对氯虫苯甲酰胺的敏感度下降有关。     

Induction of glutathione S-transferase by phenobarbital and pesticides in various house fly strains and its effect on toxicity

The effect of phenobarbital and certain pesticides on glutathione S-transferase activity was investigated. The maximum amount of enzyme induction occurred 96 hr after phenobarbital treatment. Chlorinated hydrocarbons were more effective inducers than the other pesticides evaluated. Phenobarbital treatment did not alter the apparent K_m value but altered the $\text{V}{}_{\mathrm{<mtext>max</mtext>}}$ value of glutathione S-transferase to 3,4-dichloronitrobenzene. The amount of reduced glutathione was not increased by phenobarbital treatment. Pretreatment of house flies with phenobarbital provides some protection against methyl parathion, methyl paraoxon, azinphosmethyl, and methidathion toxicity.     

Fall armyworm [Spodoptera frugiperda (J.E. Smith)] damage in maize: management options for flood-recession cropping smallholder farmers

Abstract

We determined fall armyworm abundance, infestation and damage on maize in smallholder farmers’ fields in the Zambezi Valley in northern Zimbabwe. Data were collected through field measurements at four sites and interviews with 101 farmers. Fall armyworm abundance ranged from 13.7 to 33.3 larvae per 30 plants, with infestation exceeding 94% and leaf, silk and tassel damage levels ranging between 25 and 50%. Most larvae on maize plants (P?<?0.05) were at instar stages 2 to 3. Estimated grain yield decrease was 58%. Echinochloa colona and Amaranthus spp. were also damaged by fall armyworm. Farmers experimented with 28 combinations of pesticides, ash, and washing powders. Sixty five percent of the farmers used restricted to highly restricted pesticides. High fall armyworm abundance, infestation and maize damage levels suggest that the Zambezi Valley could become a fall armyworm hotspot. Sequential damage of plant parts signified the persistence of this pest in the study area. We recommend large-scale interventions that include chemical and biological control methods as well as destroying ratoon hosts, publishing information about locally available pesticides for the control of fall armyworm, and farmer training on fall armyworm biology and correct use of pesticides.