Lepidopteran Pests Research Articles

Molecular Diagnostics for Monitoring Insecticide Resistance in Lepidopteran Pests

Chemical control methods to prevent crop damage have long been directly implicated in the selection of lepidoptera insect populations resistant to insecticides. More recently, new products featuring different modes of action (MoA), developed to mitigate the negative effects of control management on both producers and the environment, are rapidly losing efficacy due to the emergence of insect resistance. Among these, certain resistances are associated with molecular changes in the genomes of pest insects that are valuable for developing molecular markers for diagnostic tools, particularly the point mutations. Molecular diagnosis represents an innovative solution for insecticide resistance management (IRM) practices, allowing for the effective monitoring of insecticide resistance. This approach facilitates decision making by enabling the timely alternation between different modes of action (MoAs). In this context, this review focuses on the major lepidopteran pests that affect globally significant crops, discussing the impacts of insecticide resistance. It gathers literature on diagnostic methods; provides a comparative overview of the advantages of different techniques in terms of efficiency, cost, precision, sensitivity, and applicability; and highlights several novel diagnostic tools. Additionally, this review explores the coffee leaf miner, Leucoptera coffeella, as an applied model to illustrate potential approaches for more effective and sustainable control strategies.

Enhances the resistance of rice to lepidopteran pests by fusing the Cry1Ca and Cry2Aa genes with self-cleavage peptide sequence.

Accumulation of two or more Bacillus thuringiensis (Bt) proteins in plant not only improves the resistance to pests and broadens the resistance spectrum of crops, but also delays the development of pest resistance. The self-cleavage peptide sequence was used to link two codon-optimized genes, so as to achieve simultaneous accumulation of two low homologous insecticidal proteins in one plant. The rice transformants accumulating Cry1Ca and Cry2Aa proteins were fed to local lepidopteran pests and the larva mortality in 5 days were 100%. The sum of Cry1Ca and Cry2Aa proteins in leaves of transformants E1C&2A-1 and E2A&1C-18 were 10.60 and 9.55 μg g-1 fresh weight (FW), respectively, and the larva mortality of fall armyworm fed on their leaves for 5 days reached 100%. For the control transformants that expressed one Bt protein, the content of Cry1Ca in leaves of transformant E1CM031 was 14.94 μg g-1 FW, and that of Cry2Aa in leaves of transformant B2A4008S was 11.90 μg g-1 FW, but the larva mortality of fall armyworm fed on leaves of E1CM031 and B2A4008S for 5 days were 77.78% and 52.78%, respectively. Although the total Bt contents in transformants expressing one Bt protein were higher than that of transformants expressing two Bt proteins, the lethality of transformants expressing one Bt protein were obviously lower than that of transformants expressing two Bt proteins. The lethal effect of accumulating both Cry1Ca and Cry2Aa proteins in rice was stronger than that of amassing Cry1Ca or Cry2Aa protein only, which meant there was synergistic effect between Cry1Ca and Cry2Aa proteins. © 2024 Society of Chemical Industry.

Genome-wide analysis of detoxification genes conferring diamide insecticide resistance in Spodoptera exigua identifies CYP9A40.

For over a decade, diamide insecticides have been effective against lepidopteran pests like beet armyworm, Spodoptera exigua (Hübner, 1808). However, the evolution of resistance poses a challenge to their sustainable use. We identified an I4790M mutation in the S. exigua ryanodine receptor (RyR) gene, but its correlation with resistance varied across the field-collected Korean populations of S. exigua. RNA sequencing and differential gene expression analysis were performed to investigate other resistance mechanisms. Diamide-resistant and susceptible strains and F1 hybrids were compared by mapping RNA-seq reads to the S. exigua reference genome. CYP9A40 was identified as a critical gene in diamide resistance due to its high expression in the resistant strains. Synergist bioassays with piperonyl butoxide supported the role of P450s in diamide metabolic resistance in S. exigua. A strong positive correlation between CYP9A40 over-expression levels (up to 80-fold) and diamide LC50 values was obtained for field-collected populations uniformly showing a 100% frequency of the RyR I4790M target-site resistance allele. To validate the function of CYP9A40 in diamide detoxification, we recombinantly expressed the gene and tested its ability to bind and degrade chlorantraniliprole as a substrate. The results confirmed its catalytic role in diamide metabolism. CYP9A40 has been identified and validated to confer metabolic resistance in Korean S. exigua populations. It works alongside the RyR target-site I4790M mutation to enhance diamide resistance. These mechanisms offer insights for resistance monitoring and support insecticide resistance management programs to improve control strategies for S. exigua.

Assessment of Lepidopteran Pest Dynamics in Maize: Dominance of Spodoptera frugiperda and Implications for Targeted Management in Himachal Pradesh, India

Maize (Zea mays L.) plays a crucial role in the agricultural economy of India, particularly in Himachal Pradesh, where it serves as a vital crop for food, feed, and fodder. This study assessed the distribution, and relative abundance of lepidopteran pests infesting maize during the kharif, 2022-23 across two agro-climatic zones of Himachal Pradesh. Surveys identified five key lepidopteran pests: Spodoptera frugiperda, Chilo partellus, Mythimna separata, Agrotis ipsilon, and Euproctis spp. Among all, S. frugiperda is the only pest occurring among the major three crop stages of maize. The findings revealed that S. frugiperda was the most dominant pest, with relative abundance values of 19.57 per cent in Zone I and 18.94 per cent in Zone II during the seedling stage, increasing to 30.87 per cent and 30.40 per cent during the vegetative stage, respectively. In contrast, other pests like C. partellus, M. separata, A. ipsilon, and Euproctis spp. exhibited variable distribution patterns, with some showing limited occurrence. In conclusion, this study underscores the necessity for targeted pest management strategies to address dominant and subdominant lepidopteran pests in maize cultivation in Himachal Pradesh. The results offer valuable insights that can inform focused pest control efforts, with the potential to significantly enhance sustainable maize production, crop resilience and overall productivity in the region.

Study on Active Components and Mechanism of Lettuce Latex Against Spodoptera Litura.

Plant latex is a sticky emulsion exuded from laticifers once the plant is damaged. Latex is an essential component of plant defense against herbivores. Lettuce (Lactuca sativa L.) in the Compositae family has relatively fewer insect herbivores compared with other leaf vegetables. The larvae of a generalist lepidopteran pest Spodoptera litura (Fabricius) avoided feeding on living lettuce plants. However, the larvae rapidly damaged the excised leaves that were unable to produce latex. Six compounds were isolated from lettuce latex. They were identified as 2,5-dihydroxybenzaldehyde (1), 3β-hydroxy-4,15-dehydrograndolide (2), annuolide D (3), lactucin (4), lactucopicrin (5), and hanphyllin (6). Bioassays showed that the inhibition rate of compound 1 (2,5-dihydroxybenzaldehyde) and 6 (hanphyllin, a sesquiterpene lactone) on the weight gain of S. litura were 52.4 % and 10 %, respectively, at the concentration of 100 μg/g. RNA-seq analyses showed that larval exposure to compound 1 down-regulated the genes associated with heterobiotic metabolism including drug metabolism-cytochrome P450, metabolism of xenobiotics by cytochrome P450, retinol metabolism, glutathione metabolism, and drug metabolism-other enzymes (mainly uridine diphosphate glucuronyltransferase, UGTs). RT-qPCR further confirmed that 33 genes in the family of carboxylesterase (CarE), P450s and UGTs were down-regulated by compound 1. The activities of CarE, P450s and UGTs in the larvae fed on diets containing compound 1 were significantly lower than those fed on control diets, with the inhibition for the three detoxification enzymes being 55.4 %, 53.9 %, and 52.9 %. These findings suggest that secondary metabolites including 2,5-dihydroxybenzaldehyde in the latex play a key role in protecting lettuce from insect herbivory.

Characterisation of indigenous entomopathogenic nematode, Steinernema abbasi PN-1 Elawad and its biocontrol potential against major lepidopteran pests

Characterisation of indigenous entomopathogenic nematode, Steinernema abbasi PN-1 Elawad and its biocontrol potential against major lepidopteran pests

Effect of temperature and soil moisture on the infectivity of four species of entomopathogenic nematodes (Steinernema and Heterorhabditis spp.) to fall armyworm, Spodoptera frugiperda (Smith)

Spodoptera frugiperda (JE Smith) is one of the most important lepidopterous pests of maize throughout the word. The implementation of management strategies for this are need of the hour. In this case the use of Entomopathogenic nematodes (EPNs) is feasible because third-instar larvae feed in the leaf whorls of maize, and sixth instar larvae pupate in the soil; these two environments are congenial for the EPNs. But temperature and soil moisture play major roles in EPNs infectivity. Therefore, in the current study, we examined temperature and soil moisture effect on the infectivity of four indigenous EPN species from India, Heterorhabditis indica NBAIIH23, H. bacteriophora NBAIRH75, Steinernema carpocapsae NBAIRS59, and S. abbasi NBAIISa01 against larvae and pupae of S. frugiperda. Present study results showed that both temperature and soil moisture affected the infectivity of H. indica, S. carpocapsae, H. bacteriophora, and S. abbasi. As the exposure time increased, all these four nematodes infectivity to larvae was increased. Six days after inoculation, H. indica caused significantly higher larval mortality (96 %) at 25 °C and 100 % mortality at 28 °C. Whereas, S. carpocapsae caused 100 % mortality at 28 °C, and 76 % mortality at 25 °C. At 32 °C, H. indica and S. carpocapsae caused 90 % and 92 % larval mortality, respectively. As the temperature decreased to 20 °C, the infectivity of both the nematodes decreased. However, H. bacteriophora and S. abbasi caused 68 % and 50 % mortality in larvae at 20 °C, respectively. Compared to other nematodes, H. indica significantly caused higher mortality in pupae at 13 % soil moisture at 28 °C. We conclude that, Heterorhabditis indica and S. carpocapsae can be utilized against S. frugiperda larvae at (25–32 °C), and pupae at (28 °C). These nematodes can also be used against pupae of S. frugiperda at 9–13 % soil moisture content. We also suggest that these EPNs species can be incorporated in the Integrated Pest Management (IPM) for S. frugiperda.

Automated lepidopteran pest developmental stages classification via transfer learning framework.

The maize crop is highly susceptible to damage caused by its primary pests, which poses considerable challenges in manually identifying and controlling them at various larval developmental stages. To mitigate this issue, we propose an automated classification system aimed at identifying the different larval developmental stages of 23 instars of 4 major lepidopteran pests: the Asian corn borer, Ostrinia furnacalis (Guenée; Lepidoptera: Crambidae), the fall armyworm, Spodoptera frugiperda (J.E. Smith; Lepidoptera: Noctuidae), the oriental armyworm, Mythimna separata (Walker; Lepidoptera: Noctuidae), and the tobacco cutworm, Spodoptera litura (Fabricius; Lepidoptera: Noctuidae). Employing 5 distinct Convolutional Neural Network architectures-Convnext, Densenet121, Efficientnetv2, Mobilenet, and Resnet-we aimed to automate the process of identifying these larval developmental stages. Each model underwent fine-tuning using 2 different optimizers: stochastic gradient descent with momentum and adaptive moment estimation (Adam). Among the array of models tested, Densenet121, coupled with the Adam optimizer, exhibited the highest classification accuracy, achieving an impressive 96.65%. The configuration performed well in identifying the larval development stages of all 4 pests, with precision, recall, and F1 score evaluation indicators reaching 98.71%, 98.66%, and 98.66%, respectively. Notably, the model was ultimately tested in a natural field environment, demonstrating that Adam_Densenet121 model achieved an accuracy of 90% in identifying the 23 instars of the 4 pests. The application of transfer learning methodology showcased its effectiveness in automating the identification of larval developmental stages, underscoring promising implications for precision-integrated pest management strategies in agriculture.

V1848I Mutation in the Voltage-Gated Sodium Channel Confers High-Level Resistance to Indoxacarb and Metaflumizone in Spodoptera exigua.

Spodoptera exigua is one of the most serious lepidopteran pests of global importance. With the intensive use of insecticides, S. exigua has evolved resistance to many insecticides, including the sodium channel blocker insecticides (SCBIs) indoxacarb and metaflumizone. In this study, we investigated the role of the V1848I mutation in the voltage-gated sodium channel (VGSC) in SCBI resistance and its inheritance patterns in S. exigua through the development and characterization of a near-isogenic resistant strain. The AQ-23 strain of S. exigua, collected in 2023 from Anqing, Anhui province of China, shows 165-fold resistance to indoxacarb compared with the susceptible WH-S strain. A frequency of 44.6% for the V1848I mutation was detected in the SeVGSC of the AQ-23 strain, while no F1845Y mutation was found. Through repeated backcrossing and marker-assisted selection, the V1848I mutation in the AQ-23 strain was introgressed into the susceptible WH-S strain, creating a near-isogenic strain named WH-1848I. This WH-1848I strain exhibits high levels of resistance to indoxacarb (146-fold) and metaflumizone (431-fold) but remains susceptible to broflanilide and spinosad compared with the WH-S strain. Inheritance analysis revealed that SCBI resistance in the WH-1848I strain is autosomal, nonrecessive, and genetically linked to the V1848I mutation. These findings establish a clear link between the V1848I mutation and SCBI resistance in S. exigua, offering valuable insights for developing molecular detection tools and resistance management strategies.

Omics Analysis of Odorant-Binding Proteins and Cuticle-Enriched SfruOBP18 Confers Multi-Insecticide Tolerance in Spodoptera frugiperda.

Spodoptera frugiperda is a notorious pest that develops a high resistance to many insecticides. Recently, insect odorant-binding proteins (OBPs) have been proven to participate in insecticide resistance. However, the functional evidence supporting the cross-link between OBPs and insecticide resistance remains unexplored. Here, we identified 50 SfruOBPs from the larval transcriptome and genome. Notably, SfruOBP18 was highly expressed in the larval cuticle and could be induced to upregulate its expression by multi-insecticides. Ligand-binding assays revealed that SfruOBP18 bound strongly with four insecticides; RNAi and insecticide bioassay demonstrated that the knockdown of SfruOBP18 did not affect larval survival and development. However, it can significantly increase the larval susceptibility to multi-insecticides, suggesting an uncommon role of SfruOBP18 in multi-insecticide susceptibility. Our study provides a comprehensive understanding of SfruOBPs and furthermore proves that a larval cuticle-enriched OBP can bind with and confer larval tolerance to multi-insecticides. SfruOBP18 could be a new insecticidal target for controlling Lepidoptera pests.

Mrlac1, an extracellular laccase, is required for conidial morphogenesis as well as the well adaptability in field of Metarhizium rileyi

Acting as an extremely promising fungal pesticide, Metarhizium rileyi exhibits robust insecticidal activity against Lepidoptera pests, particularly the larvae. Though there is a slight delay in efficacy, biopesticides offer salient advantages over traditional chemical pesticide especially in environmental safety, cyclic infection and resistant inhibition. In this study, an exterior T-DNA was randomly inserted into the genome of M. rileyi, resulting in the acquisition of a mutant strain that displayed a colour transition from green to yellow within its conidia. The disruption of Mrlac1, a laccase, has been confirmed to attribute to the epigenetic alterations. Mrlac1 is a secreted protein harboring an N-terminal signaling peptide that undergoes in vivo synthesis and accumulates on the cell wall of M. rileyi. Targeted knock-out mutant exhibited alterations not just in conidia coloration, but significantly diminished capacity to withstand external stressors, particularly non-biological factors such as high humidity, Congo red exposure, and UV radiation. The disruptant suffered a constraint on hyphal polar growth, alteration in conidial surface structure, as well as noticeable increase in adhesion forces between conidia, the core infection factors. There is a remarkable diminution in virulence of Mrlac1 deletion variant against larvae of Spodoptera litura by topical inoculation, but not hemolymph injection. Our findings suggest that Mrlac1 acts as a positive regulator in the normal morphogenesis of fungal conidia, encompassing pigment production, inter-conidia adhesion, and conidial cell wall integrity, while the preservation of these structures holds paramount importance for the survival and infection of M. rileyi in the field.

Anthranilic diamide compatibility with the parasitoid Trichogramma chilonis Ishii (Hymenoptera: Trichogrammatidae): based on Toxicity, Two-sex life table and ecological parameters

Egg parasitoid wasps of genus Trichogramma Westwood are effective natural enemies of lepidopteran pests in various crops. However, the efficacy of Trichogramma parasitoids is adversely affected by insecticides applied in the field to manage these lepidopteran pests. To overcome this problem efficiently, there is an urgent need to incorporate insecticide-resistant Trichogramma strains into integrated pest management (IPM) programs. This study assessed the potential of Trichogramma chilonis Ishii to develop chlorantraniliprole resistance and characterized resistance associated fitness costs and stability. Toxicity bioassays were performed on T. chilonis using a dry film residue method. After 39 selections, a 573.64-fold level of resistance to chlorantraniliprole was developed in the resistant strain of T. chilonis (Chlr-R) when compared with a chlorantraniliprole susceptible strain (Chlr-S). Chlorantraniliprole resistance in Chlr-R resulted in a female biased sex-ratio and significantly increased the total life span and longevity of the adult female when compared to the Chlr-S strain. Based on age-stage, two-sex life table all the demographic parameters of Chlr-R increased significantly. These results indicate that T. chilonis can be mass reared and selected for chlorantraniliprole resistance under laboratory conditions, is an important step to improve the in field-based effectiveness and integration of these wasps with chemical control.

Effects of anthranilic diamide insecticides on metamorphosis in the common toad Rhinella arenarum (Hensel, 1867) at concentrations found in aquatic environments

ABSTRACT Anthranilic diamides (AD) are a modern class of insecticides used as alternatives to pyrethroids and neonicotinoids, particularly against lepidopteran pests. Despite their widespread use and presence in surface waters, little is known regarding their effects on amphibians. The aim of this study was to examine the effects of environmentally-relevant concentrations of AD insecticides chlorantraniliprole (CHLO) and cyantraniliprole (CYAN) on metamorphosis of the toad Rhinella arenarum. Tadpoles were exposed to CHLO or CYAN at concentrations ranging from 5 and 5000 µg/L from stage 27 until metamorphosis completion. Both insecticides produced a non-monotonic acceleration of the time required for individuals to progress through development and a decrease in the proportion of individuals completing metamorphosis, although a delay in metamorphosis was also observed at 5 µg/L of CHLO. Snout-vent length and body weight of metamorphosed toads were not markedly affected by either insecticide. CHLO was more toxic than CYAN, with a lowest observed effect concentration (LOEC) for CHLO on time to metamorphosis defined as 5 µg/L compared to 5000 µg/L for CYAN. The LOEC for reduced metamorphic success defined as 50 µg/L for CHLO compared to 500 µg/L for CYAN. As most effects occurred after stage 39, when metamorphosis depends upon thyroid hormones, it is conceivable that that AD insecticides act as endocrine disruptors. These findings suggest that contamination of surface waters with CHLO and CYAN may disrupt amphibian development in the wild and warrant further research to investigate the possibility of endocrine-disruption by ADs.

Resistance of Bt and Non-Bt Soybean Cultivars Adapted to Novel Growing Regions of Brazil to Chrysodeixis includens and Spodoptera frugiperda.

Soybean is a highly valuable commodity crop for Brazil's economy. However, it faces significant threats from the attack of a complex of lepidopteran pests, particularly Chrysodeixis includens (Walker) and Spodoptera frugiperda (J. E. Smith). These pests have been managed primarily using transgenic Bt soybeans, but limited knowledge exists about the resistance levels of Bt and non-Bt cultivars adapted to novel soybean-growing areas in Brazil, such as the Minas Gerais state. This study evaluated the resistance levels of Bt and non-Bt soybean cultivars to C. includens and S. frugiperda, and whether the Bt cultivars can differentially affect these pests across larval stages. No-choice bioassays were conducted using Bt (NS6010 IPRO and P97R50 IPRO) and non-Bt soybeans (UFLA 6301 RR, P96R90 RR, and ANsc 80111 RR) at V4-stage in the laboratory with neonate (24 h) and third-instar larvae. Larvae were fed leaf discs in Petri dishes, recording the mortality, leaf consumption, and weight gain after 7 days. There was high mortality of C. includens neonates on the Bt cultivars, but this trend was not observed for older larvae. For S. frugiperda neonates, there was high mortality on the Bt cultivar NS 6010 IPRO and non-Bt cultivar UFLA 6301 RR, but only the former was effective for older larvae. Although the Bt cultivars did not kill the third instars, antinutritional effects were found, such that leaf tissue consumed was not converted to larval weight gain. These findings are important for defining regional strategies of integrated and resistance management of C. includens and S. frugiperda in expanding regions of soybean cultivation in Brazil.

Microbial Community Structure and Metabolic Function in the Venom Glands of the Predatory Stink Bug, Picromerus lewisi (Hemiptera: Pentatomidae).

The predatory stink bug, Picromerus lewisi (Hemiptera: Pentatomidae), is an important and valuable natural enemy of insect pests in their ecosystems. While insects are known to harbor symbiotic microorganisms, and these microbial symbionts play a crucial role in various aspects of the host's biology, there is a paucity of knowledge regarding the microbiota present in the venom glands of P. lewisi. This study investigated the venom glands of adult bugs using both traditional in vitro isolation and cultural methods, as well as Illumina high-throughput sequencing technology. Additionally, the carbon metabolism of the venom gland's microorganisms was analyzed using Biolog ECO metabolic phenotyping technology. The results showed 10 different culturable bacteria where the dominant ones were Enterococcus spp. and Lactococcus lactis. With high-throughput sequencing, the main bacterial phyla in the microbial community of the venom glands of P. lewisi were Proteobacteria (78.1%) and Firmicutes (20.3%), with the dominant bacterial genera being Wolbachia, Enterococcus, Serratia, and Lactococcus. At the fungal community level, Ascomycota accounted for the largest proportion (64.1%), followed by Basidiomycota (27.6%), with Vishniacozyma, Cladosporium, Papiliotrema, Penicillium, Fusarium, and Aspergillus as the most highly represented fungal genera. The bacterial and fungal community structure of the venom glands of P. lewisi exhibited high species richness and diversity, along with a strong metabolism of 22 carbon sources. Functional prediction indicated that the primary dominant function of P. lewisi venom-gland bacteria was metabolism. The dominant eco-functional groups of the fungal community included undefined saprotroph, fungal parasite-undefined saprotroph, unassigned, endophyte-plant pathogen, plant pathogen-soil saprotroph-wood saprotroph, animal pathogen-endophyte-plant pathogen-wood saprotroph, plant pathogen, and animal pathogen-endophyte-epiphyte-plant pathogen-undefined saprotroph. These results provide a comprehensive characterization of the venom-gland microbiota of P. lewisi and demonstrate the stability (over one week) of the microbial community within the venom glands. This study represents the first report on the characterization of microbial composition from the venom glands of captive-reared P. lewisi individuals. The insights gained from this study are invaluable for future investigations into P. lewisi's development and the possible interactions between P. lewisi's microbiota and some Lepidopteran pests.

A Vip3Af mutant confers high resistance to broad lepidopteran insect pests

A <scp>Vip3Af</scp> mutant confers high resistance to broad lepidopteran insect pests

Sublethal and transgenerational effects of tetraniliprole on the tomato pinworm Phthorimaea (=Tuta) absoluta (Lepidoptera: Gelechiidae)

Invasive pest species of economic importance often require intensive pesticide use, leading to recurrent problems of pesticide resistance. Such is the case with the tomato pinworm, Phthorimaea (=Tuta) absoluta (Meyrick) (Lepidoptera: Gelechiidae), requiring the use of new insecticidal compounds for their management. Tetraniliprole, a novel insecticide effective against lepidopteran, coleopteran, and dipteran pests, is a potential alternative against the tomato pinworm. This study investigates the sublethal effects of tetraniliprole on the development and reproduction of the parental (F0) and progeny (F1) generations of P. absoluta while exploring the underlying mechanisms. Sublethal tetraniliprole exposure extended larval duration and reduced pupation rate, emergence rate, hatchability, and fecundity in both the F0 and F1 of P. absoluta. Additionally, the life-table parameters of the F1 generation were significantly altered, with decreases in net reproductive rate (R0) and increases in the mean generation time (T), leading to decreases in the intrinsic rate of population growth (r). The relative fitness of F1 insects exposed to tetraniloprole was reduced compared to unexposed insects (0.63 and 0.49, respectively). Furthermore, the mRNA expression levels of reproduction-related genes such as TaVg and TaVgR were down-regulated in the tetraniliprole-exposed insects. Finally, insect exposure to tetraniloprole increases the activity of the antioxidant enzymes such as glutathione S-transferase (GSTs), catalase (CAT), and superoxide dismutase (SOD). Taken together, these findings suggest that sublethal concentrations of tetraniloprole adversely affect both the development and reproduction of P. absoluta, providing a foundation for optimizing pest control strategies.

Biology of Trichogramma chilonis under varying conditions and their parasitism efficiency in lepidopteran pests

Biology of Trichogramma chilonis under varying conditions and their parasitism efficiency in lepidopteran pests

Insecticidal and Anti-Feedant Activity of Clerodendrum Extracts on Growth and Development of Castor Spiny Caterpillar, Ariadne merione

The castor spiny caterpillar Ariadne merione (F.) is a major lepidopteran pest affecting castor (Ricinus communis) crops mainly by causing defoliation which in turn reduces the photosynthesis and yield. The conventional pest control methods have been based on chemical control which although has been effective, has its drawbacks of being hazardous to the environment and human health besides leading to resistance by the pests. The present work aims at investigating the possibility of using Clerodendrum inerme, a plant belonging to the Lamiaceae family, as an eco-friendly solution for pest management. Insecticidal and anti-feedant efficacy of C. inerme leaf extracts, which were prepared using solvents hexane, acetone, and petroleum ether, was tested against A. merione larvae using leaf dip bioassay under no-choice situation. The findings showed that the hexane extract had the highest insecticidal (73%) and anti-feedent (97%) action. The petroleum ether extract also showed moderate insecticidal (50%) and anti-feedant activity (48%) but not as potent as the acetone extract having insecticidal and anti-feedant action of 60 and 74 per cent respectively. The results imply that C. inerme extracts, especially the hexane extract, could be used as botanical insecticides in IPM programs as a natural replacement for chemical insecticides.

Succession of Major Pests and Predatory Fauna in Okra

Investigations on pest succession in okra crops were carried out during kharif, 2023 at the Department of Entomology, B. A. College of Agriculture, Anand Agricultural University, Anand. Pest succession based on crop growth stages showed that the population of sucking insect-pests viz., jassid (Amrasca biguttula biguttula Ishida), aphid (Aphis gossypii Glover), whitefly (Bemisia tabaci Gennadius.) observed from vegetative stage and remained up to crop matured while, red spider mite, Tetranychus cinnabarinus incidence appeared from reproductive stage to maturity stage. Among the lepidopteran pests, the infestation of semi-looper, Anomis flava (Fabricius) started in the second week after germination and remained till maturity of the crop whereas, shoot and fruit borer (Earias insulana Boisd.) and fruit borer (Helicoverpa armigera (Hubner) Hardwick) damaged the crop from the vegetative stage and remained up to crop maturity. Coccinellids and spider activity initiated with sucking insect-pest incidence and remained up to crop maturity. The weather parameters, Bright sunshine hours and maximum minimum temperature had significant relationships with A. biguttula biguttula, T. cinnabarinus, E. vittella and H. armigera. Whereas, relative humidity significantly negatively influenced the activity of red spider mite, E. vittella, H. armigera and positively on predator coccinellids. Furthermore, windspeed had a significant positive association with A. biguttula biguttula and E. vittella (shoot damage) while, negative with H. armigera larva.