Contact and fumigant toxicities of calamusenone isolated from Acorus gramineus rhizome against adults of Sitophilus zeamais and Rhizopertha dominica

Abstract Calamusenone [3,8‐dimethyl‐5‐(1‐methylethylidene)‐1,2,3,4,5,6,7,8‐octahydroazulene‐6‐one, C₁₅H₂₂O] from Acorus gramineus Soland rhizome was tested in the laboratory for its insecticidal activities against adults of Sitophilus zeamais Motsch. and Rhizopertha dominica (Fab.), using dry film contact and fumigation methods. Responses varied with insect species, dosage and exposure time. In the dry film contact experiment, the highest insecticidal effects of calamusenone against S. zeamais and R. dominica adults were produced at 170.32 μg/cm² after treatment for 72 h, with 96.2% and 98.7% mortalities, respectively. The median lethal concentration (LC₅₀) (72 h) values of calamusenone against S. zeamais and R. dominica adults were 67.00 μg/cm² and 77.30 μg/cm², respectively. As a potential fumigant, calamusenone showed moderate insecticidal effect on the adults of S. zeamais and R. dominica in fumigation experiment, with their LC₅₀ (120 h) values of 125.71 μL/L and 93.64 μL/L respectively. Calamusenone isolated from A. gramineus rhizome showed promise as a novel pesticide candidate for stored‐product pest control.     

An insect model for assessing oxidative stress related to arsenic toxicity

The potential usefulness of an insect model to evaluate oxidative stress induced by environmental pollutants was examined with trivalent arsenic (As³⁺, NaAsO₂) and pentavalent arsenic (As⁵⁺, Na₂HAsO₄) in adult female house flies, Musca domestica, and fourth-instar cabbage loopers, Trichoplusia ni. M. domestica was highly susceptible to both forms of arsenic following 48 h exposure in the drinking water with LC₅₀s of 0.008 and 0.011% w/v for As³⁺ and As⁵⁺, respectively. T. ni larvae were susceptible to dietary As³⁺ with an LC₅₀ of 0.032% w/w but seem to tolerate As⁵⁺ well with an LC₅₀ of 0.794% concentration after 48 h exposure. The minimally acute LC₅ dose of both As³⁺ and As⁵⁺ varied considerably but averaged 0.005% for both insects. The potential of both valencies of arsenic for inducing oxidative stress in the insects exposed ad libitum to approximately LC₅ levels was assessed. The parameters examined were the alterations of the antioxidant enzyme activities of superoxide dismutase (SOD), catalase (CAT), glutathione transferase (GST), the peroxidase activity of glutathione transferase (GSTPX), and glutathione reductase (GR), and increases in lipid peroxidation and protein oxidation. SOD (1.3-fold), GST (1.6-fold), and GR (1.5-fold) were induced by As³⁺ in M. domestica but CAT and GSTPX were not affected. As⁵⁺ had no effect on M. domestica. In T. ni, the antioxidant enzyme activities were not affected by As³⁺ except for SOD which was suppressed by 29.4% and GST which was induced by 1.4-fold. As⁵⁺ had no effect except the suppression of SOD by 41.2%. Lipid peroxidation and protein oxidation, which represent stronger indices of oxidative stress, were elevated in both insects by up to 2.9-fold. However, based on the antioxidant enzyme response to the arsenic anions, the mode of action of arsenic induced oxidative stress may differ between the two insects. Until this aspect is further clarified, evidence at this time favors the prospect of As³⁺ as a pro-oxidant, especially for M. domestica. © 1995 Wiley-Liss, Inc.     

Evaluation of larvicidal potential of certain insect pathogenic fungi extracts against Anopheles stephensi and Culex quinquefasciatus

Fungal metabolites are attracting attention as potential microbial insecticides, and they are anticipated to overcome the problems of pesticide resistance and environmental pollution that are associated with the indiscriminate use of conventional synthetic insecticides. The relative bioefficacies of selected fungal pathogens, Aspergillus flavus, A. niger, A. parasiticus, Fusarium sporotrichoides and Penicillium verrucosum were observed against Anopheles stephensi and Culex quinquefasciatus larvae. A. flavus demonstrated the greatest bioefficacy with 50% lethal concentration (LC₅₀) values of 9.54 and 10.98 ppm against Anopheles stephensi and Culex quinquefasciatus larvae, respectively, after 24‐h exposure. The bioefficacy of A. flavus increased in both species with an exposure time of 48 h, with LC₅₀ values of 7.26 and 8.55 ppm, respectively.     

Larvicidal activity of acetone extract and green synthesized silver nanoparticles from Allium sativum L. (Amaryllidaceae) against the dengue vector Aedes aegypti L. (Diptera: Culicidae)

Mosquito vectors of major human diseases are currently controlled using chemical and biological products. Extensive insecticide use has led to resistance development and human/environmental health risks, and alternative sustainable control options are needed; in this study, activity of an extract of garlic (Allium sativum; Amaryllidaceae), and silver nanoparticles (AgNPs) synthesized from the extract, were evaluated against 2nd and 3rd instar larvae of the yellow fever mosquito, Ae. aegypti (Diptera: Culicidae). Synthesis of AgNPs was confirmed using UV–Vis spectroscopy, and characterised using powdered X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. Larvae were exposed to five concentrations (50, 100, 150, 200, 250 ppm) of garlic extract or synthesized AgNPs, with distilled water and silver nitrate solution (1 mM) as controls. The mortality of larvae was recorded after 6, 12, 24, 36, and 48 h following addition of the respective extracts.Dose- and time-dependent toxicity were recorded in both treatment groups with no mortality in control groups. Exposure to AgNPs at 250 ppm for 48 h yielded 100% mortality for both larval instars, with corresponding LC₅₀ values of 44.77 (2nd) and 62.82 ppm (3rd). Exposure to garlic extract resulted in similar 48-hour mortality (99 ± 0.77% (2nd) and 98 ± 1.10% (3rd), but consistently higher LC₅₀ values after all exposure times compared to AgNPs (e.g. 48-hour exposure: 108.42 ppm (2nd), 129.11 ppm (3rd), suggesting that AgNPs may potentially be used at lower concentrations for Ae. aegypti control.     

Direct and indirect effects of simulated calcareous dredge material on eggs and larvae of pink snapper Pagrus auratus

The direct and indirect effects of a simulated, calcarenite‐based dredge material on eggs and larvae of pink snapper Pagrus auratus were assessed. Direct effects were assessed by measuring hatch rate or survival of eggs and pre‐feeding larvae, respectively, over a range of concentrations and exposure durations. Exposure of eggs to suspended solid concentrations up to 10 000 mg l^?1 for 24 h did not affect egg buoyancy or hatch rate, despite sediment adherence occurring at the two highest concentrations tested. Newly hatched larvae, whose mouths were still closed, were relatively tolerant of suspended solids, with a 12 h lethal concentration resulting in 50% mortality, LC₅₀, of 2020 mg l^?1 and a first observable effect concentration of 150 mg l^?1. Once the larvae's mouths opened, tolerance was significantly reduced, with a 12 h LC₅₀ of 157 mg l^?1 and a first observable effect concentration of 4 mg l^?1. Tolerance of larvae to suspended solids was negatively correlated with suspended solids concentration and exposure time, with exposure durations of ≤6 h being significantly less detrimental than those of 9 h or more. Indirect effects to larvae were assessed by measuring ingestion of copepod nauplii by 10 and 15 days post‐hatch (dph) larvae at sediment concentrations from 0 to 200 mg l^?1 in 50 mg l^?1 increments over 4 h. Ingestion was not significantly affected by sediment for 10 dph larvae, but by 15 dph, sediment had a far greater impact on ingestion, with larvae in all sediment treatments eating significantly fewer copepods than those in the control.     

Larvicidal activity of Pseudocalymma alliaceum and Allium sativum against Culex quinquefasciatus (Say)

The larvicidal activity of the plant extracts Pseudocalymma alliaceum and Allium sativum were determined against Culex quinquefasciatus. The hexane extract of P. alliaceum and the petroleum ether extract of A. sativum exhibited larvicidal efficacy against Cx. quinquefasciatus larvae. Extracts of P. alliaceum resulted in concentrations that produced 50% mortality LC₅₀ and LC₉₀ values of 2.49 and 15.06 ppm, respectively, after 24 h and 1.16 and 8.45 ppm after 48 h. Extracts of A. sativum resulted in LC₅₀ and LC₉₀ values of 8.38 and 29.15 ppm after 24 h and 7.28 and 44.19 ppm after 48 h of exposure, respectively. The results indicate that the plant extract component(s) present in the hexane extract of P. alliaceum leaves demonstrated greater potential as an efficient larvicide than A. sativum against Cx. quinquefasciatus.     

Ovicidal and Deleterious Effects of Cashew (Anacardium occidentale) Nut Shell Oil and Its Fractions on Musca domestica,Chrysomya megacephala,Anticarsia gemmatalis and Spodoptera frugiperda

In this work, we evaluated the ovicidal activity and the deleterious effects of cashew (Anacardium occidentale) nut shell oil and its fractions on the development of Musca domestica and Chrysomya megacephala, important vectors of several diseases. The insecticidal effects of this plant were also measured on the first and second instar larvae of Anticarsia gemmatalis and Spodoptera frugiperda, soy and maize pests, respectively. The fly eggs and the crop pest insect larvae were exposed to the cashew (Anacardium occidentale) nut shell liquid (CNSL) and its fractions: technical CNSL, anacardic acid, cardanol and cardol. The results show that the cardol fraction, for both species of flies, presented the lowest lethal concentration with LC₅₀ of 80.4 mg/L for M. domestica and 90.2 mg/L for C. megacephala. For the mortality of the larvae of A. gemmatalis and S. frugiperda, the most effective fraction was anacardic acid with LC₅₀ of 295.1 mg/L and 318.4 mg/L, respectively. In all species, the mortality rate of the commercial compounds (cypermethrin 600 mg/L and temephos 2 mg/L) was higher than that of the evaluated compounds. Despite this, the results obtained suggest their potential in field trials, once the fractions of A. occidentale presented high mortality at low lethal concentrations in laboratory conditions, with the possibility of integrated use in the control of disease vectors and agricultural pests, employing ecofriendly compounds.     

Synergistic activity of Bacillus thuringiensis δ‐endotoxin and TMOF against Culex pipiens and Spodoptera littoralis larvae

Trypsin Modulating Oostatic Factor (TMOF) is a decapeptide hormone that inhibits the biosynthesis of digestive enzymes in the mosquito midgut. The hormone inhibits food digestion and ultimately leads to starvation and death. It has been used as a biological insecticide to control mosquitoes. In an attempt to increase the insecticidal activity of TMOF, a combination of CryIC (δ‐endotoxin from Bacillus thuringiensis) and TMOF was determined. Eight recombinant proteins fused with GST (glutathione‐S‐transferase) were expressed in Escherichia coli cells. Their insecticidal activities were determined against Culex pipiens and Spodoptera littoralis larvae. Purified GST‐TMOF and its analogue GST‐YDPAS exhibited a moderate toxicity on C. pipiens larvae with LC₅₀ of 145.9 and 339.9 μg/mL, respectively. Unexpectedly, no mortality was observed in first instar larvae of S. littoralis. Puirified GST‐TMOF and GST‐YDPAS together with Bt toxin showed a synergistic toxic effect on both Culex and Spodoptera larvae. In the presence of 100 μg/mL GST‐TMOF and GST‐YDPAS, the median lethal concentration of entomocidus on culex larvae decreased from 52.1 to 16.7 and 31.9 μg/mL, respectively. Likewise, GST‐TMOF and GST‐YDPAS incorporated with 0.07 μg/cm² of enotmocidus showed insecticidal activity against S. littoralis with LC₅₀ of 16.4 and 21.9 μg/cm². The E. coli lysates containing GST‐CryIC and its 3′‐truncated version showed low toxicity against the lepidopteran insect (10.8 and 16.6 μg/cm²) compared to 0.15 μg/cm² of the native crystalline form of CryIC. Similarly, the mosquitocidal activity of the recombinant Bt toxins was low.     

Efficacy of bioactive compounds from Curcuma longa L. against mosquito larvae

To identify larvicidal compounds from the ethanolic extracts of Curcuma longa root, the active compounds were isolated using activity‐guided fractionation with column chromatography and identified based on nuclear magnetic resonance (NMR) and mass spectrometry (MS) data. The dipping method was used to determine the larvicidal activities of each compound against 4th‐instar larvae of Culex pipiens pallens. Two compounds were isolated and identified, ar‐turmerone and 8‐hydroxyl‐ar‐turmerone. The two compounds exhibited larvicidal activities against the 4th‐instar larvae of C. pipiens pallens after 24 hr of treatment with LC₅₀ values of 138.86 and 257.68 ppm, respectively. The larvicidal activities of ar‐turmerone and 8‐hydroxyl‐ar‐turmerone against C. pipiens pallens are reported herein for the first time. The elucidation of the structure of these phytochemicals and their insecticidal activities are important for assessing the potential of this plant as a botanical insecticide.     

THE BIOLOGICAL ACT'IVITIES OF YELLOW AZALEA,RHODODENDRON MOLLE G. DON AGAINST THE VEGETABLE LEAFMINER,LIRIOMYZA SATIVAE (DIPTERA: AGROMYZIDAE) *

Abstract The results of laboratory and greenhouse bioassays indicated that Rhodojaponin‐ III (Abbr. R‐ 1) and extracts of flowers from Rhododendron molle G. Don possessed signficant feeding inhibition and insectcidal properties against the larvae and adults of Liromyzia sativae. Treated with 500 mg/L R‐ III 1 000 mg/L molosul‐tap, and 10 000 mg/L methanol(MeOH) ethyl acetate (EtOAc), CH₂Cl₂, methanol‐water (MeOH‐H₂O) extracts the rates of feeding inhibition were 77. 34 % 74.30 % 82.15 % 77.50 % 67. 33 % 62.85 % against the 2nd instar larvae, and were 67.66% 55.21 % 49.72% 54.26% 46.81 % 38.53% against the 3rd instar larvae, respectively;LC₅₀ values against the 2nd instar larvae were 208.65, 166.05, 2.74 ± 10³,766.72, 5.95 ± 10³, 1.85 ± 10³mg/L, and against 3rd larvae were 300.62, 256.00, 4.33 ±10³, 1.03 ± 10³,9.79 ± 10³, and 2.62± 10³mg/L, respectively. Against the adults, LC₅₀ values of R‐III EtOAc extract and molosultap were 159.07.723.87 and 134.55mgL respectively after treatment for 24 h.     

Comparative study of three herbal formulations against dengue vectors Aedes aegypti

The efficacy of three formulations (i.e., natural lavender crude, essential oil, and gel) extracted from Lavender angustifolia was tested against vectors of the epidemic dengue virus, Aedesaegypti, to evaluate their larvicidal activity effect. The ethanolic extract of the lavender crude was prepared using a rotary evaporator, while the other extracts, such as essential oil and gel, were obtained from iHerb, a supplier of medicinal herbs in the US. The mortality rate of larvae was evaluated 24 h after exposure. Larvicidal activity of the lavender crude was 91% mortality at 150 ppm, 94% for essential oil at a concentration of 3000 ppm, and 97% for lavender gel at a 1000 ppm. Natural lavender crude was one of the most promising extracts tested against Ae.aegypti larvae, with lethal concentrations at LC₅₀ and LC₉₀ of 76.4 and 174.5 ppm post-treatment. The essential oil had the least effect on mosquito larvae, with LC₅₀ and LC₉₀ reaching 1814.8 and 3381.9 ppm, respectively. The lavender gel was moderately effective against Ae. aegypti larvae, with LC₅₀ and LC₉₀ values reaching 416.3 and 987.7 ppm after exposure. The occurrence of morphological abnormalities in the larvae treated with the three compounds, in turn, resulted in an incomplete life cycle. Therefore, our results indicated that natural lavender crude displayed the highest larvicidal activity against larvae, followed by gel and essential oil. Thus, this study concluded that lavender crude is an effective, eco-friendly compound that can be used as an alternative to chemical products to control vector-borne epidemic diseases.     

Design,Synthesis, Insecticidal Activities and Molecular Docking of Sulfonamide Derivatives Containing Propargyloxy or Pyridine Groups

The discovery of new highly active molecules from natural products is a common method to create new pesticides. Celangulin V targeting Mythimna separate (M. separate) midgut V-ATPase H subunit, has received considerable attention for its excellent insecticidal activity and unique mechanism of action. Therefore, combined with our preliminary work, thirty-seven sulfonamide derivatives bearing propargyloxy or pyridine groups were systematically synthesized to search for insecticidal candidate compounds with low cost and high efficiency on the H subunit of V-ATPase. Bioactive results showed that compounds A2-A4 and A6-A7 exhibited a better bioactivity with median effective concentration (LC₅₀) values (2.78, 3.11, 3.34, 3.54 and 2.48 mg/mL, respectively) against third-instar larvae of M. separate than Celangulin V (LC₅₀=18.1 mg/mL). Additionally, molecular docking experiments indicated that these molecules may act on the H subunit of V-ATPase. Based on the above results, these compounds provide new ideas for the discovery of insecticides.     

Fumigant toxicity of essential oil of Mugwort (Artemisia vulgaris L.) against three major stored product beetles

Application of plants essential oil for the evaluation of their fumigant toxicity and insecticidal properties is the goal of many researches. In this study, aerial parts of Artemisia vulgaris L. were subjected to hydrodistillation using a Clevenger-type apparatus, and the chemical composition of the volatile oils was studied by gas chromatography–mass spectrometry. Alpha-Pinene (23.56) was the main component of the essential oil. Insecticidal activity of the oil was evaluated against Tribolium castaneum (Herbst), Callosobruchus maculatus (F.) and Rhizopertha dominica (F.) after 24, 48 and 72 h. After 24-h exposure time, C. maculatus was more susceptible (LC₅₀ = 52.47 μl/l air) and T. castaneum was more tolerant (LC₅₀ = 279.86 μl/l air) than other species. LT₅₀ values were indicated using highest concentration of LC₅₀ tests for three species. In general, mortality increased as the doses of essential oil and exposure time increased. These results proposed that A. vulgaris oil might have potential as a control agent against T. castaneum, R. dominica and especially C. maculates in storages.     

Boric acid‐induced immunotoxicity and genotoxicity in model insect Galleria mellonella L. (Lepidoptera: Pyralidae)

Boric acid (BA) is widely used in various industrial process and can be accessed to nontarget organisms. This study aimed to investigate the insecticidal effects of BA and its toxic activities with respect to immunologic and genotoxic effects using Galleria mellonella larvae as a model. BA concentrations (78.125–10,000 ppm) were administrated to the larvae using the feeding method. Concentration‐dependent mortality was observed in all larval groups. Probit analysis revealed LC₃₀, LC₅₀, and LC₇₀ values to be 112.4, 320.1, and 911.4 ppm, respectively. These concentrations were used in all bioassays. Drastic reductions in total hemocyte counts along with changes in differential hemocyte counts were observed following BA treatment. Cell viability assays showed dose‐dependent reductions in viable cells and an increase in the necrotic and apoptotic ratios after BA treatment. However, mitotic indices of larval hemocytes did not change at all BA concentrations. The cytotoxic effect of BA led to a significant reduction in cellular immune responses such as encapsulation, melanization, and nodulation activities of treated larvae. While BA increased micronucleus ratios at the highest concentration, comet parameters indicating DNA damage increased in G. mellonella larval hemocytes at all concentrations. These report that BA suppresses the immune system of G. mellonella and also poses risks of genotoxicity at high concentrations.     

Effect of diethyl maleate on the toxicity of essential oil from Citrus reticulata fruit peels to Tribolium castaneum Herbst under laboratory conditions

Certain compounds of plants, essential oils, with insecticidal properties have been considered as alternatives to chemical pesticides for pest control in recent years. In this study, the synergistic effect of diethyl maleate (DEM) on the toxicity of Citrus reticulata Blanco (Rutaceae) peel essential oil against a stored-product insect pest, i.e. red flour beetle, Tribolium castaneum Herbst (Tenebrionidae) adults was studied. DEM [one part], combined with acetone [two parts], was applied on T. castaneum adults. Five concentrations of essential oil from C. reticulata were tested. Three replicates and 30 adult insects/replicate/each concentration were used. LC₅₀ values after 24 and 48?h of exposure were 33.8 and 28.2?μl/l air, respectively. Combination of the essential oil from C. reticulata with the synergist DEM after 24 and 48?h of exposure decreased the corresponding LC₅₀ values to 18.1 and 12.2?μl/l air, respectively. These results revealed that DEM can considerably improve the potency of essential oil from C. reticulata and maybe applied successfully in the stored-product pest control programmes.     

Comparative larvicidal activity of essential oils from three medicinal plants against Aedes aegypti L

This work aimed at comparing larvicidal activity of essential oils extracted from the dried leaves of Alpinia speciosa, Cymbopogon citratus, and Rosmarinus officinalis against Ae. aegypti larvae. The larvae were observed for 4 h and at 24 h according to a completely randomized design with three replications and the following concentrations [μl/ml]: 0.25, 0.5, 1.0, 1.5, 2.0, 2.5, and controls were distilled water, and commercial standard citral, camphor, eucalyptol, α‐pinene, and β‐myrcene. The essential oil of C. citratus had the lowest LC₅₀ (0.28) and LC₉₀ (0.56) values, followed by that of A. speciosa (0.94 and 1.2, resp.) and of R. officinalis (1.18 and 1.67, resp.), and only the commercial standards citral and α‐pinene were larvicidal.     

The toxicity of endod extract to the early life stages of Dreissena bugensis

Toxicity bioassays were conducted on embryos and early larvae of quagga mussels, Dreissena bugensis, using a filtered aqueous extract and a lyophilized butanol extract of the soap berry plant Phytolacca dodecandra. Developmental stages exposed to each extract were embryos to trochophores (ca 3h‐17h), trochophores to D‐hinge larvae (ca 17h‐40h) and embryos to D‐hinge (3h‐ca 40). Over the whole embryo to D‐hinge exposure period, the aqueous extract resulted in a lowest observed effective concentration (LOEC) of 5mgl^‐1 although mortality did not exceed 50%. For the butanol extract, the LOEC was 2mgl^‐1 and the LC₅₀ was 2.1 mgl^‐1. For the aqueous extract, most of the endod toxicity was seen at the embryo stage, whereas for the butanol extract the toxicity was associated with the trochophore stage. Compared with other non‐oxidizing commercial molluscicides, endod has only moderate toxicity to early dreissenid life stages.     

Detoxification,antioxidant, and digestive enzyme activities and gene expression analysis of Lymantria dispar larvae under carvacrol

Carvacrol is a terpene compound with various biological activities. However, few studies have specifically focused on its insecticidal activity and mechanism of carvacrol. The larvae of Lymantria dispar are seriously harmful herbivorous insect. This study measured the antifeedant, growth-inhibitory, and toxic effects of carvacrol on L. dispar larvae. To further clarify the insecticidal mechanism of carvacrol, the effects of carvacrol on detoxifying enzymes, antioxidative enzymes, digestive enzyme activities, and the mRNA expression of the above-mentioned enzyme genes were investigated. The results of the study showed that the median lethal concentration (LC₅₀) and the sublethal concentration (LC₂₀) of carvacrol were 1.120 mg/mL and 0.297 mg/mL, respectively, at 72 h. After LC₂₀ treatment of L. dispar larvae for 72 h, food intake and weight gain were significantly lower compared with the control. Enzyme activity assays showed that carvacrol significantly inhibited the activities of carboxylesterase (CarE), glutathione S-transferase (GST), and acetylcholinesterase (AchE), and the inhibition rate of AchE activity was highest (66.51%). Carvacrol also activated the activities of superoxide dismutase (SOD) and catalase (CAT), while it inhibited the activities of lipase (LIP) and amylase (AMS), and first inhibited and then activated protease. In addition, qRT-PCR tests showed that carvacrol affected the mRNA expression levels of CarE, GST, AchE, SOD, CAT, LIP, AMS, and protease. This study helps to clarify the insecticidal mechanism of carvacrol on L. dispar larvae.     

Inductive and synergistic interactions between plant allelochemical flavone and Bt toxin Cry1Ac in Helicoverpa armigera

Genetically engineered crops simultaneously produce defensive allelochemicals and Bacillus thuringiensis (Bt) toxin proteins to kill some of the world's most devastating insect pests. How the two types of toxins, when ingested sequentially or simultaneously, interact at both lethal and sublethal doses in these pests remains underexplored. Here, we examined the toxicological interactions between the Bt toxin Cry1Ac and the flavonoid allelochemical flavone in Helicoverpa armigera. Simultaneous exposure of H. armigera neonates to lethal doses (LC₂₅) of Cry1Ac and flavone caused a mortality significantly higher than that of either toxin alone and their expected additive mortality. Preexposure for 24 h to a sublethal dose (LC₁₀) of Cry1Ac followed by 6-d simultaneous exposure to the same dose of Cry1Ac plus a lethal dose (1.6 mg/g diets, LC₅₀) of flavone resulted in a mortality significantly higher than that of the LC₅₀ dose of flavone alone and the expected additive mortality of the LC₅₀ dose of flavone plus the LC₁₀ dose of Cry1Ac. One-day preexposure to the sublethal dose (LC₁₀) of flavone followed by 6-d simultaneous exposure to the LC₅₀ dose (6 ng/cm²) of Cry1Ac plus the LC₁₀ dose of flavone yielded a mortality significantly higher than that of the LC₅₀ dose of Cry1Ac but similar to the expected additive mortality of the LC₅₀ dose of Cry1Ac plus the LC₁₀ dose of flavone. The results suggest that Cry1Ac induces and synergizes the toxicity of flavone against H. armigera larvae.