Instar Larvae Of Plutella Xylostella Research Articles

Laboratory Evaluation of the Insecticidal Toxins from Entomopathogenic Nematode Symbiotic Bacteria to Control Vegetable Diseases and Pests

Aims: Entomopathogenic nematode (EPN) and its symbiotic bacterium are used worldwide as microbial control agents. Toxins from EPN symbiotic bacteria were isolated and provided basis for using this potential resource as biocontrol agent against vegetable diseases and pests.
 Study Design: The toxins were extracted from 28 strains of bacteria associated with entomopathogenic nematodes. The insecticidal activity and antibiotic activity against vegetable diseases and pests were determined through bioassay.
 Place and Duration of Study: College of Bioscience and Biotechnology, between May 2020 and September 2021.
 Methodology: The toxins were extracted by (NH4)2SO4 precipitation method. The insecticidal activities and antibiotic activities were evaluated using bioassay in the laboratory.
 Results: The toxins of the symbiotic bacteria associated with EPN had certain insecticidal activities on the first instar larvae of Plutella xylostella and Laphygma exigua, and strain SY5 showed the most obvious antifungal activities against Trichothecium roseum and Fusarium oxysporum.
 Conclusions: The toxins of the EPN symbiotic bacteria SY5 had good insecticidal activity and antibiotic activity. Therefore, it has the potential for use against vegetable diseases and pests as biocontrol agents.

Evaluation of colloidal chitosan against diamond back moth Plutella xylostella L. on cauliflower

An ecofriendly colloidal chitosan byproduct synthesized from crude chitosan was evaluated for its chronic toxicity against second instar larvae of Plutella xylostella L. by leaf dip bioassay. The consumption of 10000 ppm colloidal chitosan treated leaf caused 100% mortality after the 4th day, with least larval weight (0.02 mg). Whereas, the consumption of 8000 ppm treated leaves reduced the larval (0.65 mg), pupal (1.26 mg), and adult weights (0.75 mg), with 10% adult malformation and extended larval duration. This is compared to untreated larval duration of 10.66 days. Thus, colloidal chitosan exhibits chronic toxicity and growth inhibition effect on P. xylostella larvae.

Development of an environmentally friendly nanoemulsion based on Ginkgo biloba exocarp extracts to control Plutella xylostella

AbstractThe chemical compositions of Ginkgo biloba exocarp extracts (GBEE) and leaf extracts are similar, however, studies describing the development of GBEE biopesticides are few. In this study, the authors investigated the preparation of GBEE nanoemulsionand and characterized by transmittance, physical stability, droplet size and size distribution for the first time. Insecticidal activity and lipophilicity screening of four different solvents indicated ethyl acetate was satisfactory. Based on dispersibility, centrifugation, heating‐cooling cycle, cloud point and long‐term stability experiments, two formulations (ethyl acetate/Tween 40‐Span 60 (9:1)/water and ethyl acetate/Tween 60‐Span 60 (9:1)/water) were optimum to formulate nanoemulsions. However, the smallest droplet size and size distribution (10.93 ± 0.16 nm, PDI = 0.15 ± 0.01) was obtained using the Tween 60/Span 60 combination. The insecticidal activity of GBEE nanoemulsion was evaluated against the third instar larvae of Plutella xylostella. Lethal concentration (LC50) values of the optimized nanoemulsion were 127.38 mg/L at 12 h and 72.80 mg/L at 24 h, respectively. This indicated that GBEE nanoemulsion had higher insecticidal activity than the GBEE. The results proposed that the GBEE nanoemulsion is a potential and effective natural alternative for the management of P. xylostella.

Potentiality of Novel Chitosan-O-Arginine as Insecticidal and Growth Inhibitory Compound against Diamondback Moth, Plutella xylostella L. on Cauliflower

Chitosan (Cs), a natural biodegradable polysaccharide polymer, prepared from sea waste of crustacean origin, has the potential for plant protection application. In the present study, a novel chitosan derivative, called Chitosan-O-Arginine, synthesized from crude chitosan, was evaluated for its chronic toxicity against second instar larvae of Plutella xylostella by leaf dip method. The results revealed the toxic potential of Chitosan-O-Arginine, which could inflict cent per cent mortality after four days of continuous feeding on the 1000 ppm treated leaf, and the larva could accomplish 0.12 mg weight (99.66% reduction) on the day before death. The next lower concentration (700 ppm) resulted in the maximum larval weight of 0.45 mg (93.71% reduction) after nine days of feeding and resulted in cent per cent mortality after the tenth day. While the untreated larva attained a maximum weight of 5.54 mg. All the larvae were pupated in the next lower concentration (500 ppm) and recorded minimum pupal (1.00 mg; 80% reduction) and adult (0.73 mg; 77.45% reduction) weight, whereas the untreated pupa and adult weighed the maximum of 5.00 mg and 3.20 mg. Considering the developmental period, there was no significant difference in the larval duration and adult life span. While there was an extension of the pupal period by one day at 500 ppm compared to untreated larva. The larval, pupal, and adult malformations were noticed in 300 and 100 ppm concentrations. These findings suggest that chitosan was potent in imposing chronic toxicity and growth inhibitory effect on P. xylostella larvae, and hence it can be recommended as an eco-friendly component in the Integrated Pest Management module.

Evaluation of insecticidal activity of Beauveria bassiana against different instar larvae of Plutella xylostella by using two different methods of application

Evaluation of insecticidal activity of Beauveria bassiana against different instar larvae of Plutella xylostella by using two different methods of application

Evaluation of Beauveria bassiana and Metarhizium anisopliae isolates against Plutella xylostella (L.) under laboratory conditions

Twenty isolates each of Beauveria bassiana and Metarhizium anisopliae were tested against the second instar larvae of Plutella xylostella through laboratory bioassay using larval dip method at the concentration of 1×10 7 conidia/ml. Higher larval mortality of 88.85% and 81.44%, were observed with NBAIR Ma-4 and NBAIR Ma-35 isolates of M. anisopliae and 77.36% with NBAIR-Bb-5a isolate of B. bassiana . Further studies on dose and time mortality with four isolates indicated lowest LC 50 value of 2.6×10 4 conidia/ml and LT 50 of 86.6 hours with NBAIR Ma-35 isolate. These isolates have to be further tested against P. xylostella in infested fields of cabbage and cauliflower.

Bio Efficacy of Bacillus thuringiensis Isolates against Diamond Back Moth (Plutella xylostella L.) on Cauliflower Plant in Tamil Nadu, India

Bacillus thuringiensis (Bt) gram positive entomopathogenic bacteria being an eco-friendly biopesticide. In present study the potential of B. thuringiensis isolates was studied for the biological control of Diamond back moth (DBM). Fifteen Bt isolates were obtained from the Department of Agricultural Microbiology, TNAU Tamil Nadu. This mainly isolated from the cultivated lands Cotton (Gossypium hirsutum), Brinjal (Solanum melongena) and Tomato (Solanum lycopersicum). All the 15 isolates were identified as B. thuringiensis based on the crystalline structure. Four different types of crystalline forms were observed, in which the isolates CC, CB1, BC, TD, BD were produces cuboidal shape crystals. Then, the isolates were characterized based on presence of lepidopteron specific cry gene. Among the 15 B. thuringiensis isolates seven of them were found to be positive for lepidopteron specific cry genes include cry 1 & cry 2. Four Bt isolates were exhibited presences of both cry 1 and cry 2 genes. The selected 4 isolates further screened for protein profiling by SDS Page. Molecular weights of the protein ranging from 65 to 130 kDa. Toxicity of this four B. thuringiensis isolates were evaluated by bioassay using third instar larvae of the diamondback moth (Plutella xylostella) and isolate (CC) recorded maximum mortality of 95.33% comparable to standard strain HD1 98.31%. In quantitative bioassay, the LC50 for third instar larvae of Plutella xylostella was found to be least range 197.09 ppm with fiducial limits of 110.28 - 352.21 ppm respectively. Different concentration of the toxic protein (100, 250, 500, 750, 1000, 2000) will reduce the leaf damage and larval growth was (54-8% and 58-25%) observed. This achieved effective control of DBM in cauliflower plant.

Insecticidal properties and chemical composition of Piper aduncum L., Lippia sidoides Cham. and Schinus terebinthifolius Raddi essential oils against Plutella xylostella L.

In the laboratory, were evaluated the effects (residual contact and feeding deterrence) of the essential oils from the leaves of Piper aduncum, Lippia sidoides and Schinus terebinthifolius, as well as eleven selected constituents and binary blends of oils in different proportions against 3rd instar larvae of Plutella xylostella (L.). The Piper oil demonstrated the greatest toxicity (LC50 = 0.31 µL/mL) and feeding deterrence (DC50 = 1.08 µL/mL) between oils tested. Dillapiole (LC50 = 1.01 µL/mL; DC50 = 1.10 µL/mL) and carvacrol (LC50 = 6.03 µL/mL; DC50 = 0.075 µL/mL) demonstrated the greatest toxicity and feeding deterrence between constituents tested, respectively. Based on the fractional effects indices for the blends, a synergistic interaction was found for the blend of the Lippia and Schinus oils at a proportion of 75 and 25%, respectively. The present findings indicate that this blend could be used in the control of P. xylostella, as the literature reports populations resistant to the active ingredient in the positive control, Premio®. Further studies are needed for the development of a new botanical insecticide based on the active ingredients in oils from L. sidoides and S. terebinthifolius to improve efficiency, stability and the cost-benefit in the control of P. xylostella.

One pot solvothermal synthesis of novel fluorescent phloem-mobile phenylpyrazole amide pesticides fused olefin moieties to enhance insecticidal bioactivities and photodegradation properties

In order to find a novel type of fluorescent phloem-mobile insecticides, a facile one-pot solvothermal strategy via fipronil addition-elimination substitution reaction with the corresponding acyl chloride derivatives has been employed to construct series of phenylpyrazole amide derivatives (PAs) fused olefin moieties in high yields. The investigation for insecticidal bioactivities of PAs against 3rd instar larvae of Plutella xylostella exhibited better activities than that of fipronil, which can be elucidated by enhanced phloem mobility and calcium ions' coordination with amide N-C=O, CC double bonds and chloride ions, extended conjugate moieties and decreasing steric hindrance of the stereoscopic structure. The introduction of amide units conferred phloem mobility to PAs, which was evaluated by the hydrophobic parameters determined with reversed-phase HPLC through the chromatographic capacity factor. By introducing conjugate moieties and organic chromophore into phenylpyrazole parent structure to increase their conjugation degree and light absorption abilities, PAs exhibited good photodegradation properties. The relationships between extended conjugate moieties of parent structure, electronegativity of substituted groups and photodegradation properties have been discussed. The olefin units connected to PAs caused electronic absorption and fluorescent wavelengths bathochromic shifted. Under simulated solar irradiation, PAs can be reconverted into fipronil parent fragments by photodegradation, thereby enhancing their insecticidal activity. The fluorescent quantum yields of PAs were almost 4 times that of fipronil, which also laid a foundation for the natural degradation and fluorescence detection of insecticide residues.

Solvothermal synthesis of novel phenylpyrazole Schiff base fluorescent insecticides fused extended conjugate units for enhancing bioactivities, photophysical and electrochemical properties

In order to find a new type of fluorescent insecticides, a series of phenylpyrazole Schiff base derivatives have been synthesized by a facile one-pot solvothermal method based on the amino group of fipronil addition-elimination condensation reaction with the corresponding benzaldehyde derivatives in high yields, which were fully characterized by 1H NMR, IR, MS and elemental analysis. Crystal structure determination indicated that 1-(2,6-dichloro-4-(trifluoromethyl)phenyl)-5-(4-fluoro-benzylidene-amino)-4-(trifluoromethylsulfinyl)-1H-pyrazole-3-carbonitrile (7) crystallized into zigzag chains by π···π packing interactions between phenyl rings of neighbouring molecules. The investigation for insecticidal bioactivities of these pesticides against 3rd instar larvae of Plutella xylostella exhibited better activities than that of fipronil, which can be elucidated by enhanced calcium ions' coordination abilities with CN double bonds and chloride ions, extended conjugated parent structure, steric hindrance of the stereoscopic structure and electronegativity of substituted groups. The electronic absorption, fluorescent and electrochemical properties of phenylpyrazole Schiff base derivatives have been systematically investigated for the first time, which all emitted blue-green light in both solution and solid state at room temperature. The relationships between extended conjugated moieties of parent structure, positions of substituent group and the kinds of substitutes at 4-position on the phenyl ring and photophysical properties have been discussed, which was confirmed by electrochemical analysis. The alteration of absorption and emission wavelengths can be rationalized by substitutes' electronegativity and Substituents’ Hammett constants. The fluorescent quantum yields of phenylpyrazole Schiff base insecticides were almost 4 times that of Fipronil, which laid a foundation for their natural degradation and fluorescence detection of pesticide residues. This approach proposes a unique insight to provide a great number of novel phenylpyrazole Schiff base fluorescent insecticides by a general green method.

Antifeedant Activities of Secondary Metabolites from Hyssopus cuspidatus Against Plutella xylostella

A new sesquiterpene hyssopusin A (1), together with four known compounds 2–5, was isolated from Hyssopus cuspidatus. The structure of hyssopusin A (1) was elucidated by physical and spectroscopic data analysis, including 1D NMR, 2D NMR, and HR-ESI-MS. Compounds 1–4 showed antifeedant effects against the third instar larvae of Plutella xylostella (Lepidoptera: Plutellidae) in a concentration-dependent manner with 50% antifeedant concentrations (AFC50) of 32.17, 38.33, 25.47, and 36.22 μg/cm2, respectively.

Insecticidal activity of sesquiterpene lactones and monoterpenoid from the fruits of Carpesium abrotanoides

The isolation of secondary metabolites produced by plants can lead to the discovery of new insecticidal agents. The aim of this study was to identify secondary metabolites from the fruits of Carpesium abrotanoides, a well-known medicinal and poisonous plant belonging to the family Asteraceae, with the potential to act as natural insecticides. Two new sesquiterpene lactones 9β-hydroxy-1βH, 11αH-guaia-4,10(14)-dien-12,8α-olide (1) and 9β-hydroxy-1βH, 11βH-guaia-4,10(14)-dien-12,8α-olide (2) along with four known sesquiterpene lactones (3-6) and one monoterpenoid (7) have been isolated. The structures of these compounds were established on the basis of 1D and 2D NMR data and HRESIMS data interpretation. To characterize their insecticidal activities, bioassays were conducted using two insect pest species of agricultural importance. Compounds 1–7 showed antifeedant effects to 3rd instar larvae of Plutella xylostella (Lepidoptera: Plutellidae) in a concentration-dependant manner with EC50 of 19.84, 42.82, 97.94, 96.90, 39.94, 37.35 and 43.99mg/L, respectively. Moreover, all of these compounds display stomach-contact combination toxicity toward 4rd instar larvae of Bradysia odoriphaga Yang and Zhang (Diptera: Sciaridae) (LD50=18.71, 80.29, 230.65, 319.67, 31.18, 40.87 and 68.47mg/L, respectively). In general, this is the first report of insecticidal activities of secondary metabolites isolated from C. abrotanoides. Moreover, compound 1 showed the best insecticidal activity in the test, demonstrating its potential to be used as a natural insecticides.

Guaiol - A Naturally Occurring Insecticidal Sesquiterpene

The dichloromethane fraction of Ferula ferulaeoides was analyzed by GC and GC-MS, and thirty-four compounds were identified. The main component in the fraction, guaiol (37.0%) was separated by chromatographic methods and identified from spectroscopic data, including 1H and 13C NMR, and X-ray crystallographic diffraction. Guaiol showed significant inhibition of aphids at a concentration of 70 mg/L. It also showed good contact activities against the 4th instar larvae of Mythimna separate and 3rd instar larvae of Plutella xylostella, with LD50 values of 0.07 and 8.9 mg/larva, as well as fumigation activity against the 4th instar larvae ofM. separata and adult Musca domestica, with LC50 values of 3.5 microL/L and 16.9 microL/L, respectively.

Evaluation of transgenic lines of Indian mustard (Brassica juncea L. Czern and Coss) expressing synthetic cry1Ac gene for resistance to Plutella xylostella

Transgenic lines of oil seed plant Brassica juncea expressing a synthetic cry1Ac gene were developed using Agrobacterium tumefaciens-mediated transformation. The integration of transgene cry1Ac in transformed plants was confirmed by Southern blot hybridization using a cry1Ac probe. Expression of transgene was analyzed using reverse transcription PCR. Inheritance of the hpt gene in transgenic plants showed the expected 3:1 Mendelian segregation ratio. An enzyme linked immuno sorbent assay revealed that Cry1Ac protein content in the leaves of transgenic plants (T0, T1 and T2) ranged from 250 to 1,800 ng mg−1 of total soluble protein. The insect bioassay study showed that transgenic plants were resistant to 2nd instar larvae of Plutella xylostella as compared to control plants and confirmed the enhanced insect resistance in Indian mustard.

Insecticidal and antifeedant effects of two alkaloids from Cynanchum komarovii against larvae of Plutella xylostella L

AbstractA bioassay‐guided fractionation of Cynanchum komarovii crude alkaloid extract led to the isolation of two alkaloids. The isolated alkaloids were identified as 7‐demethoxytylophorine (1) and 6‐hydroxyl‐2,3‐dimethoxy phenanthroindolizidine (2) based on the comparison of their spectroscopic characteristics with the literature data. Insecticidal, antifeedant and growth inhibitory effects of these two alkaloids against the 3rd instar larvae of Plutella xylostella L. (Lepidoptera: Plutellidae) were examined. The results showed that alkaloid 1 was more toxic than alkaloid 2 against the 3rd instar larvae of Plutella xylostella L., but both alkaloids were less toxic than the total alkaloid fraction. For antifeedant activity, alkaloid 1 showed AFC50 of 1.82 mg/ml at 24 h after treatment, alkaloid 2 showed 3.89 mg/ml, while total alkaloids showed 1.56 mg/ml. In dipping toxicity test, alkaloids 1 and 2 produced 93.3% and 63.3% mortality at 72 h after treatment, respectively, while total alkaloids produced 96.7% mortality. The LC50 values for alkaloids 1, 2 and the total alkaloids were 3.54, 9.21 and 2.63 mg/ml, respectively. The development of larvae was also inhibited, and the growth inhibition rates at the concentration of 15.00 mg/ml were 92.8%, 78.2% and 98.6% for alkaloids 1, 2 and total alkaloids, respectively, at 72 h after treatment. Compared with antifeedant and dipping effect, the alkaloids 1, 2 and total alkaloid fraction revealed weak feeding toxicity, and their corrected mortality rates at the concentration of 15.00 mg/ml were 60.0%, 40.0% and 63.3% at 7 days after treatment. The LC50 values for alkaloids 1, 2 and total alkaloids were 12.58, 32.37 and 8.88 mg/ml, respectively, at 7 days after treatment.

Ser-Substituted Mutations of Cys Residues in Bacillus thuringiensis Vip3Aa7 Exert a Negative Effect on its Insecticidal Activity

Vegetative insecticidal proteins (VIPs), which were produced by Bacillus thuringiensis during its vegetative growth stage, display a broad insecticidal spectrum to Lepidoptera larvae. Sequence alignment of the Vip3A-type indicates that three cysteine residues were conserved in Vip3A-type proteins. To determine whether these conserved cysteine residues contributed to the insecticidal activity, the three residues were respectively substituted with serine in the Vip3Aa7 protein by site-directed mutagenesis. Bioassays using the third instar larvae of Plutella xylostella showed that the toxicity of C401S and C507S mutants were completely abolished. To find out the inactivity reason of mutants, three mutants and the wild-type Vip3Aa7 were treated with trypsin. The results indicated that the C507S mutant was rapidly cleaved and resulted in decrease of the 62kDa toxic core fragment. These results indicated that the replacement of the Cys(507) with a Ser(507) caused decrease in C507S resistance against trypsin degradation. It is suggesting a possible association between insecticidal activity and trypsin sensitivity of Vip3A proteins. This study serves a guideline for the study of Vip3A protein structure and active mechanism.

Fusing the vegetative insecticidal protein Vip3Aa7 and the N terminus of Cry9Ca improves toxicity against Plutella xylostella larvae

Bacillus thuringiensis insecticidal crystal proteins (ICPs) and vegetative insecticidal proteins (VIPs) have been widely used as a kind of safe bio-insecticides. A problem that has been of concern worldwide is how to improve their insecticidal activities. In this study, to determine the synergism between VIPs and ICPs effect on insecticidal activity, a construct that produces a chimeric protein of the Vip3Aa7 and the N terminus ofCry9Ca, named V3AC9C, was expressed in Escherichia coli BL21 cells. In additional experiments, the V3AC9C chimeric protein, the single Vip3Aa7, and the single N terminus of Cry9Ca were treated with trypsin. SDS-PAGE showed that the V3AC9C could be processed into two single toxins. Bioassays tested on third instar larvae of Plutella xylostella showed that the toxicity of the chimeric protein was markedly better than either of the single toxins. Interestingly, the toxicity of the chimeric protein was 3.2-fold higher than a mixture of the Vip3Aa7 and Cry9Ca toxins (mass ratio of 1:1). The synergism factor (SF) of chimeric protein containing Vip3Aa7 and Cry9Ca was calculated to be 4.79. The SF in mixture of toxins is only 1.46. Hence, the effect was more than the sum of the Vip3Aa7 and Cry9C activities. Analysis of the protein's solubility showed that the Vip3Aa7 helped the N terminus of Cry9Ca to dissolve in an alkaline buffer. It was concluded that the increase in the toxicity of the V3AC9C chimeric protein over the constituent proteins mainly resulted from this increase in solubility. These results lay a foundation for the development of a new generation of bio-insecticides and multi-gene transgenic plants.

Antifeedant and larvicidal activities of Acalypha fruticosa Forssk. (Euphorbiaceae) against Plutella xylostella L. (Lepidoptera: Yponomeutidae) larvae

Antifeedant and larvicidal activities of hexane, chloroform and ethyl acetate extracts of Acalypha fruticosa Forssk. Leaves were studied using leaf disc no-choice method against third instar larvae of Plutella xylostella L. Chloroform extract showed maximum antifeedant activity of 92.8% at 5% concentration with a LC50 value of 1.86%. Nine fractions were collected from the chloroform extract (30g) by silica gel column chromatography, among which the seventh fraction (eluted by 100% ethyl acetate) recorded maximum antifeedant activity (84.3%) at 1000 ppm concentration with a LC50 value of 385.7 ppm against the third instar larvae of P. xylostella. Preliminary phytochemical analysis of this effective fraction showed the presence of terpenoids, tannins, coumarins, anthraquinones and saponins.

Heterologous Expression and Purification of Cry1Ac22 Toxin from <i>Bacillus thuringiensis</i> W015-1

A cry1Ac22 gene was amplified by PCR from Bacillus thuringiensis strain W015-1 isolated from diapausing larvae of silkworm ( Bombyx mori ). The full-length gene was ligated into the prokaryotic expression vector pQE30 to construct the recombinant plasmid pQE30-Cry1Ac22 . The pQE30-Cry1Ac22 was transformed into competent cell of E.coli host strain M15 and then induced by IPTG to express His-tag-Cry1Ac22 fusion protein. The results showed that the His-tag-Cry1Ac22 was highly heterologous expressed in the presence of inclusion bodies in E.coli cell. Inducing experiments with different IPTG concentrations and temperatures revealed that the optimum condition for the expression of the fusion protein was 1 mmol/L IPTG and 28℃. SDS-PAGE analysis demonstrated that the host with pQE30-Cry1Ac22 generated a 133 kD His-tag-Cry1Ac22 fusion protein. The His-tag-Cry1Ac22 fusion protein was purified with affinity chromatography on a Ni 2 + -NTA resin column. Larvacidal assays were performed and showed that the engineered bacterial lysate and purified protein exhibited high insecticidal activity against second instar larvae of Plutella xylostella . This study might provide a basis for the preparation of antibody and for the determination of insecticidal activity using heterologous Cry1Ac22 protein.

Two chemical derivatives of bacterial metabolites suppress cellular immune responses and enhance pathogenicity of Bacillus thuringiensis against the diamondback moth, Plutella xylostella

Eicosanoids mediate insect immune responses, especially against bacterial infection. Phospholipase A 2 (PLA 2) catalyzes the committed step of the eicosanoid biosynthesis pathway. Three PLA 2 inhibitors have been identified from metabolites of an entomopathogenic bacterium, Xenorhabdus nematophila: benzylideneacetone (BZA), Pro-Tyr (PY), and acetylated Phe-Gly-Val (Ac-FGV). Interestingly, they share benzenepropane as a core chemical structure. We analyzed the functional significance of the core structure using structural derivatives. Removing a phenyl ring from PY resulted in significant loss of the PLA 2 inhibitory activity, as seen in a Pro-Ala derivative. Though the p-hydroxyl group was not critical in PY as seen in Pro-Phe derivative, its addition to BZA resulted in significant loss of inhibitory activity. Some alterations of structures other than the core structure increased PLA 2-inhibitory activity in some derivatives, including Ala-Tyr (AY) and Phe-Gly-Val (FGV) derivatives. Using these selected derivatives, we further analyzed synergistic effects on pathogenicity of Bacillus thuringiensis (Bt) against the second instar larvae of Plutella xylostella. These two derivatives significantly enhanced the Bt pathogenicity. This study introduces two novel compounds that inhibit PLA 2 and suggests their application in combination with Bt to control P. xylostella.