4th Instars Research Articles

Cabbage Leaf Epicuticular Wax Deters Female Oviposition and Larval Feeding of Pieris rapae

The small white butterfly Pieris rapae is a major pest of brassicaceous crops, causing extensive damage to cabbage Brassica oleraceae var. capitata. Pieris rapae utilizes glucosinolates, which are characteristic of brassicaceous plants, for host selection. However, the effect of epicuticular wax of cabbage leaves on host selection by P. rapae remains unclear. This study was aimed to determine the effects of leaf epicuticular wax on female oviposition and larval feeding of P. rapae. We used a common cabbage variety ‘Kinkei 201’ containing n-nonacosane as the predominant leaf wax component. Wax removal treatments, in which the leaf surface was rubbed with cotton balls, significantly increased female oviposition and mid-stage (2nd–4th instars) larval feeding compared with untreated (intact) leaves. Spraying treatments with n-nonacosane standard on wax-removed leaves significantly suppressed female oviposition and mid-stage larval feeding. Thus, n-nonacosane in cabbage leaf epicuticular wax potentially affects host selection and preference by P. rapae. In contrast, final-stage (5th instar) larvae significantly preferred intact leaves to wax-removed leaves, and spraying treatments with n-nonacosane did not significantly change their feeding on wax-removed leaves. This suggests that young larvae are more susceptible to wax feeding inhibition than older larvae and that increasing leaf wax content enhances the resistance of cabbage against P. rapae. Acquiring these traits in cabbage leaves through improved breeding and cultivation methods may reduce and control the oviposition and feeding damage by P. rapae.

The Effects of Temperature and Diet on Population Dynamics and Reproduction in Ephestia elutella (Hübner) (Lepidoptera: Pyralidae)

ABSTRACTEphestia elutella (Hübner) (Lepidoptera: Pyralidae), an omnivorous pest with a wide range of hosts, is responsible for the damage and loss of many stored commodities. However, the parasitoid wasp Habrobracon hebetor (Say) (Hymenoptera: Braconidae) utilises 5th instars of E. elutella larvae to breed. In order to support the large‐scale production of E. elutella for research and parasitoid rearing, we explored the effects of diet (artificial diet and tobacco) on the mortality, developmental duration, adult longevity, fecundity, and population parameters of E. elutella reared at 19°C, 22°C, 25°C, 28°C, and 31°C using age‐stage, two‐sex life tables. Increasing the temperature from 19°C to 31°C significantly affected the stage‐specific mortality, reproductive parameters, and population parameters of E. elutella. Specifically, both developmental duration and adult longevity decreased with increasing temperature. For both diets, pre‐adult mortality was lowest at 25°C but was lower overall in populations fed an artificial diet. The developmental duration, adult longevity, and mean generation time (T) were significantly lower in populations fed an artificial diet, whereas the intrinsic rate of increase (r) and finite rate of increase (λ) were significantly lower in populations fed tobacco leaves. Temperature appears to have a significant effect on the development and reproduction of E. elutella, and a combination of 25°C and artificial diet may be the most conducive to large‐scale breeding. This study provides a theoretical basis for the mass rearing of E. elutella to support pest control applications in tobacco warehouses.

Transcriptomic insights on impaired survival and enhanced pesticide susceptibility following knockdown of Syntaxin5 in Locusta migratoria

Transcriptomic insights on impaired survival and enhanced pesticide susceptibility following knockdown of Syntaxin5 in Locusta migratoria

Insecticidal activity of Delonix regia (Fabaceae) against the cotton leafworm, Spodoptera littoralis (Bois) with reference to its phytochemical composition

Overuse of synthetic pesticides causes problems for humans and the environment or leads to insect resistance to insecticides, so plant extracts and essential oils have gained popularity as an environmentally acceptable alternative to chemical pesticides. This study investigated the toxicity of Delonix regia leaf and seed extracts, protein patterns, and genetic distance analysis against the 5th instar larvae of cotton leafworm, Spodoptera littoralis Boisaduval. Methanol, petroleum ether, and acetone extracts of leaves and seeds of D. regia were used to coat castor leaves for ingestion by the 5th instar of S. littoralis larvae. The seeds’ methanol and petroleum ether extracts were the most effective (100 and 98 Mortality%), with LC50 values of 0.887 and 1.795 g/L, respectively, 24 h post-treatments. Data showed that D. regia extracts affected consequences of protein changes compared to untreated S. littoralis larvae resulted in genetic changes, as well as inhibition of the insect’s important α-amylases, forming protein complexes, and influencing normal growth and development. GC-MS analysis of the chemical composition of the seed extract revealed 18 compounds with high levels of stigmasterol, 2-methyl-4-vinylphenol, benzoic acid, 3-hydroxy, and squalene with percentages of 43.07%, 21.33%, 14.51%, and 14.12%, respectively. As a result, we concluded that D. regia seed extracts had the potential to control Spodoptera littoralis larvae.

Functional investigation of CYP304F1 in Tuta absoluta (Lepidoptera: Gelechiidae) by RNA interference.

Tuta absoluta has developed resistance to many biological insecticides, causing substantial agricultural and economic losses annually. P450s have been the most extensively studied enzymes in the context of insecticide metabolism in insect pests, and the detoxification metabolism of P450s in T. absoluta against biological insecticides remains poorly understood. In T. absoluta, CYP304F1 was screened from the comparative transcriptome of 2 regional populations in Xinjiang, China. The objective of the present study was to characterize and analyze CYP304F1 of T. absoluta and explore its role in detoxification of spinetoram as well as the growth and development of T. absoluta. Following cloning and sequence analysis of the target gene, it was named CYP304F1. Expression levels of CYP304F1 were then determined after spinetoram exposure and across various developmental instars and tissues. Finally, dsCYP304F1 was synthesized and utilized to assess the effects of post-RNAi on larval spinetoram susceptibility, growth, and development. Sequence analysis revealed that CYP304F1 harbors conserved domains characteristic of P450 proteins, exhibiting high conservation within the Lepidoptera clade. Treatment with an LC50 dose of spinetoram significantly upregulated CYP304F1 expression in T. absoluta larvae. Silencing CYP304F1 significantly enhanced larval susceptibility to spinetoram and prolonged leaf-mining duration and developmental time from the 2nd instar to 4th instar by 40% and 17.6%, respectively, compared to controls. And feeding on dsCYP304F1-treated leaves for 6 days resulted in 71% larval mortality. These results suggested that CYP304F1 played a crucial role in detoxification of spinetoram as well as in the growth and development of T. absoluta larvae.

The role of gut microbiota at different developmental stages in the adaptation of the Etiella zinckenella to a plant host

Insect gut symbiotic microbiota play a crucial role in the nutritional, physiological, and behavioral aspects of their hosts, providing valuable insights for investigating the co-evolution of insects and plants. Sophora alopecuroides L. serves as an important windbreak plant, while Etiella zinckenella is a major pest that infests its seeds. However, the structure of the gut microbiota community in E. zinckenella remains poorly understood. In this study, we analyzed the gut microbiota of E. zinckenella across different developmental stages—larvae (1st—5th instars), pupae, and adults—infesting S. alopecuroides using 16 S rRNA high-throughput sequencing. The results revealed that the dominant phyla throughout the development of E. zinckenella were Proteobacteria and Bacteroidota, although the dominant genera varied significantly across stages. Diversity analysis of gut microbiota at different developmental stages indicated that microbial diversity was significantly higher in the larval stage compared to the pupal and adult stages. Functional predictions further highlighted the richness of metabolic pathways within the gut microbiota of E. zinckenella. Notably, carbohydrate metabolism functions were significantly more abundant during the larval stage, while lipid metabolism functions were substantially lower. Our findings demonstrate dynamic changes in the composition and diversity of the gut microbiota across the developmental stages of E. zinckenella, underscoring the critical roles of these bacteria during specific stages of the insect’s life cycle. This study lays the groundwork for future strategies aimed at controlling E. zinckenella through modulation of its gut microbiota, offering significant theoretical implications.

Biological control of Schistocerca gregaria and Locusta migratoria migratorioides using Entomopathogenic bacteria

This study investigated the potential of indigenous entomopathogenic bacterial (EPB) strains from Egypt to control the two most prevalent locust species, Schistocerca gregaria (Forsskål) (Orthoptera: Acrididae), and Locusta migratoria migratorioides (Reiche & Fairmaire) (Orthoptera: Acrididae). To assess the efficacy of the EPB strains, experiments were conducted in the laboratory, semi field, and field. The results showed that Xenorhabdus nematophila (Thomas et Poinar) BA2 (Enterobacterales: Morganellaceae) and Photorhabdus luminescens (Thomas et Poinar) EGAP3 (Enterobacterales: Morganellaceae) were the most effective strains against S. gregaria and L. migratoria migratorioides in laboratory settings. Under semi-field conditions, X. nematophila BA2 recorded nymphal mortality rates of 89.31% and 85.00% against the 2nd and 5th nymph instars of S. gregaria, respectively, and P. luminescens EGAP3 showed nymphal mortality rates of 88.00% and 80.00% against the 2nd and 5th nymph instars of S. gregaria, respectively. In field trials, X. nematophila BA2 exhibited the highest nymphal mortality rate of 88.70% at 7 days after spraying. Overall, the findings of this study suggest that X. nematophila BA2 and P. luminescens EGAP3 are promising candidates for environment-friendly, safe locust pest management. Further research is needed to explore and develop these bacteria for commercial use in agriculture.

The Effect of Humidity and the Role of Visual Cues During Feeding on Green/Brown Color Polyphenism in Locusta migratoria.

The regulation of body color in locusts comprises phase polyphenism, green/brown polyphenism, and homochromy. Humidity was believed to control green/brown color polyphenism in locust species. However, recent findings indicate that humidity has minimal influence on this polyphenism in Schistocerca gregaria nymphs reared in isolation. This study investigated the effects of humidity and visual stimuli on Locusta migratoria nymphs reared in isolation. When L. migratoria nymphs were fed either Bromus catharticus or Dactylis glomerata leaves only during the dark period, the proportions of green nymphs at the 5th instar were comparable. Increased humidity (through addition of moist cotton) induced more green morphs under a 16-h dark/8-h light cycle, suggesting that humidity is involved in green/brown polyphenism in L. migratoria. However, these nymphs were not sensitive to humidity regarding this polyphenism under a 23-h dark/1-h light cycle, suggesting that sensitivity is related to visual cues. The daily overlap between food availability and light periods for 12 h resulted in a higher proportion of green morphs than a daily overlap for only 4 h, suggesting that such an overlap affects green/brown polyphenism in this species. Although we were unable to assess the effect of the total food availability period on polyphenism in this study, we confirmed that at least (1) humidity and (2) visual cues during feeding are associated with green/brown polyphenism in L. migratoria. These regulations may have ecological significance for this species, allowing them to phenotypically adjust to the seasonal and spatial variation in their environment, increasing their chances of survival.

Toxicological, Biochemical and Histological Studies on the Fall Armyworm, Spodoptera frugiperda Treated with Five Insecticides

Saleh, H.A., S.F. Abd El-Rahman, M.A. Batt and H.R.K. Ali. 2024. Toxicological, Biochemical and Histological Studies on the Fall Armyworm, Spodoptera frugiperda Treated with Five Insecticides. Arab Journal of Plant Protection, 42(4): 489-496. https://doi.org/10.22268/AJPP-001280 Fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith) is one of the most important, invasive, and destructive pests. It was reported for the first time on maize plants in 2019 in upper Egypt. A bioassay was conducted to evaluate the toxicity of 5 insecticides (Protecto 9.4% WP, Pesover 90% SP, Punkron 20% EC, Uphold 36% SC and Full 48% EC) against 2nd and 4th instar larvae of this pest under laboratory conditions. All tested insecticides were more efficient against the 2nd instar larvae than the 4th instars. Punkron was the most efficient pesticide against the 2nd instar larvae, with LC50=0.0039 g/L, whereas Uphold showed higher toxicity than the other insecticides against the 4th instar larvae (LC50=0.0524 g/L) 5 days after treatment. The effect of the tested insecticides on the activities of acetylcholine esterase (AChE), carboxylesterase (CE), glutathione S-transferase (GST) and Alpha & beta esterase enzymes was determined. All tested insecticides induced the activity of AChE and CE in the 4th instar larvae. On the other hand, the insecticides decreased GST activity, while increased the activity of Alpha & beta esterase enzymes in the same instar larvae, except for the insecticide Full (Chlorpyrifos). All insecticides induced histological alterations (e.g., structure of the muscle layers, disorganization in the epithelial cells, and cell fragmentation) in the midgut, damaging the digestive cells and peritrophic matrix, affecting digestion and nutrient absorption. The tested insecticides in this study may play a prominent role in the integrated management program of the fall armyworm. Keywords: Spodoptera frugiperda, insecticides, bioassay, biochemical activity, histology

Field evaluation of the delivery system of native predatory bug, <i>Eocanthecona furcellata</i> for the management of lepidopteran pests in pulse crops

Eocanthecona furcellata (Hemiptera: Pentatomidae) is predatory on most of the lepidopteran insect pests. This bug has been recorded in different regions of India from various crop ecosystems. In Uttarakhand, this predator has been found predating upon different pests of various crops viz. pulses, wheat, rice, soybean, maize, etc grown in plains, foothills, mid hills, valleys and high hills. The mass production technology of this predator has also been developed in the laboratory on hosts such as Spodoptera litura and Corcyra cephalonica. Further, the different release methods in crop fields and rates of release of this insect were studied on pulse crops. Cage experiments were conducted to evaluate the effective predacious stages of this bug and its field release doses in different pulse crop ecosystems. The experiments were carried out in the tarai region of Uttarakhand during 2020-2022. The results revealed that 4th and 5th nymphal instars as well as the adults were voracious feeders in the pulse ecosystem. The population of Maruca vitrata on mungbean and pigeonpea was reduced significantly by 4th and 5th nymphal instars as compared to other stages of the insect. Thus, the nymphal and adult stages were found to be appropriate to be employed for the management of insect pests in pulse crops. The experiments were also conducted on the dose determination in which different rates as 2, 3, 6, 9, 12 and 15 nymphs and adults per cage were used for the control of S. litura. The results revealed a 62.00 and 54.13% reduction of S. litura population in soybean, 60.89 and 62.50% in pigeonpea, 63.99 and 60.02% in mungbean in S. litura population was found at 10 days after release of the nymphs and adults of the bug respectively at the rate of 9 nymphs and 9 adults per cage. The present results indicate that the releasing rates of 9 nymphs and 9 adults per cage in the pulse ecosystem were satisfactory for suppressing S. litura population. This study will be of significant importance in achieving successful management of lepidopterous insect pests through field release of the predator at specified doses.

Synthesis and modification of novel thiazole-fused quinoxalines as new insecticidal agents against the cotton leafworm Spodoptera litura: design, characterization, in vivo bio-evaluation, toxicological effectiveness, and study their mode of action.

Herein, novel thiazolo[4,5-b]quinoxalin-2-ones 2-6 and thiazolo[4,5-b]quinoxalin-2(3H)-imines 7-9 were synthesized and characterized using elemental analysis, IR spectroscopy, and 1H/13C NMR to confirm their structures. The efficacy of the newly designed thiazolo-quinoxalines 2, 3, 4, 5, 7, 8, and 9 against the cotton leafworm S. litura (2nd and 4th instar larvae) was evaluated, and results revealed insecticidal activity with variable and good mortality percentages. A SAR study was also discussed. Additionally, compound 3 exhibited the highest insecticidal activity, with mortality% values ranging from 86% ± 7.21% to 97% ± 1.52% and from 66.00% ± 6.24% to 86.33% ± 6.90% at concentrations of 625-2500 mg L-1 against the 2nd and 4th instar larvae, respectively. The probit analysis revealed that the thiazolo[4,5-b]quinoxalin-2(3H)-one derivative 3, after 5 days of treatment, exhibited LC50 values of 141.02 and 366.73 mg L-1 for the 2nd and 4th instar larvae, respectively. The LT50 values ranged from 0.52 to 1.92 days for the 2nd larval instar and from 1.95 to 2.47 days for the 4th larval instar. The corresponding toxicity index (TI) values were 86.21% for the 2nd instar and 78.47% for the 4th instar larvae. The mode of action of compound 3 was assessed through physiological, histological, and SEM analyses on the 4th larval instar. The physiological bioassay revealed a significant increase in total carbohydrate and protein levels compared to the control group. However, the enzymatic study showed a significant decrease (P < 0.05) in the levels of aspartate aminotransferase (AST/GOT), alanine aminotransferase (ALT/GPT), and alkaline phosphatase (AlP), while acetylcholinesterase (AChE) levels significantly increased. SEM analysis revealed malformations in the external body, while histological examination demonstrated severe damage to the gut epithelium and regenerative cells in the midgut tissues.

Mass Rearing and Biological Characteristics of Galleria mellonella L. (Lepidoptera: Pyralidae) Using an Artificial Diet

Galleria mellonella L. is an important pest of honeybees. The primary objective of the study is mass-rearing Galleria mellonella using a modified artificial diet. Globally, Galleria baiting technique with larvae of the greater wax moth, G. mellonella L., is the most commonly used method for recovering entomopathogenic fungi and infective-stage juveniles of entomopathogenic nematodes from soil. Therefore G. mellonella was mass reared at laboratory condition using modified method of Birah et al. (2008) by artificial diet. The mean larval duration for the 1st, 2nd, 3rd, 4th, 5th, 6th and 7th instar was 3.2 ± 0.08, 5.2 ± 0.13, 6.1±0.39, 5.6 ± 0.26, 7.4 ± 0.13, 7.6 ± 0.21, 8.5 ± 0.47 days respectively. The mean pupal period was 8.1 ± 0.29 days. The total developmental period was 73.56 ± 1.27 days. Mean fecundity was 680 ± 42.5 numbers, larval weight was 19.98 ± 0.91 mg for 7 days old larva, 376.48 ± 6.52 mg for 14 days old larva, mean pupal weight was 393.33 ± 6.81 mg and adult emergence was 91.15 ± 3.97 per cent.

Synergistic Effect of Three Medicinal Plant Extracts and Their Nutritional Indices on the Tribolium castaneum Herbst and Ephestia kuehniella Zeller

Chemical control of stored pests causes environmental pollution, contamination of stored products and endangering human health. Botanical compounds are one of the suitable alternatives for this aim. In this study effects of eucalyptus, rosemary and mentha extracts alone and in mixed of them on T. castaneum and E. kuehniella were evaluated. Due to our research, the most effect of rosemary extract on the T. castaneum adult, and eucalyptus on the 3rd and 4th instars larvae of E. kuehniella observed. The most significant synergetic on the T. castaneum adult was the combination of ME, MR and ER. Also, the most synergetic effect of extracts on the 3rd and 4th instar larvae of E. kuehniella were related to ME, and MR and ME respectively. The lowest amount of T. castaneum adult Feeding deterrence percentage indices (FDI) and Approximately Digestibility (AD) were observed in rosemary extract and the lowest amount of Efficiency of conversion of ingested food (ECI), Relative consumption rate (RCR) and The Relative growth rate (RGR) was related to eucalyptus extract. The lowest amount of E. kuehniella larvae FDI was observed in rosemary extract and the lowest amount of ECI, RGR and AD was related to eucalyptus extract. Therefore, these botanical extracts can be used to control these two important stored pests.

Functional Analysis of Two Carboxylesterase Genes Involved in Beta-Cypermethrin and Phoxim Resistance in Plutella xylostella (L.)

Enhanced expression of carboxylesterase (CarE) genes is an important mechanism of insecticide resistance in pests. However, their roles in multi-insecticide resistance have rarely been reported. Herein, two CarE genes (PxαE6 and PxαE9) were identified; their relative expression levels in three multi-insecticide-resistant populations of P. xylostella (HN, GD-2017 and GD-2019) were 2.69- to 15.32-fold higher than those in the sensitive population, and they were considerably overexpressed at the larval stage and in the midgut of the 4th instar. PxαE6 and PxαE9 knockdown increased the susceptibility of GD-2019 larvae to phoxim or/and beta-cypermethrin. The recombinant PxαE6 and PxαE9 expressed in Escherichia coli exhibited high hydrolysis activity towards α-NA. GC–MS and LC–MS/MS assays revealed that PxαE9 could metabolize beta-cypermethrin and phoxim with efficiency determinations of 51.6% and 21.1%, respectively, while PxαE6 could metabolize phoxim with an efficiency of 12.0%. Homology modelling, molecular docking and molecular-dynamics simulation analyses demonstrated that beta-cypermethrin or/and phoxim could fit well into the active pocket and stably bind to PxαE6 or PxαE9. These results show that PxαE6 and PxαE9 overexpression were involved in resistance to beta-cypermethrin or/and phoxim in multi-insecticide-resistant P. xylostella populations, a finding which sheds light on the molecular mechanisms of multi-insecticide resistance in insect pests.

Nano-chitosan as a bio-enhancer for improving insecticide formulations: A study on indoxacarb and methomyl against cotton leafworm

Nano-chitosan as a bio-enhancer for improving insecticide formulations: A study on indoxacarb and methomyl against cotton leafworm

Assessment of Biology and Fertility Life Table of Coccinella septempunctata Linnaeus Predating on Mustard Aphid, Lipaphis erysimi Kaltenbach

Lipaphis erysimi (Kalt.), commonly known as the mustard aphid (Homoptera: Aphididae), is the most notorious, globally distributed, and obligatory ectoparasite of many field crop including rapeseed and mustard. An investigation was carried out to assess the biology and fertility life table of Coccinella septempunctata in Bio-control lab, Department of Entomology at CCS Haryana Agricultural University, Hisar following the standard protocol at the laboratory condition of temperature (T) 25±2°C, relative humidity (RH) 65±5% RH, and 16:8 light:dark (L:D). Biological studies revealed that Coccinella septempunctata (L.), predatoryfemale laying eggs either singly or in masses (546.90 eggs/female) were vibrant yellowand spindle shape with an incubation period of 3.50 days. Hatchability was 86.00±5.62 per cent. There were four grub instars followed by pre-pupal stage, mean grub duration of 1st, 2nd, 3rd and 4th instar was 1.68±0.47, 3.18±0.60, 3.08±0.65 and 5.02±0.73 days. Total grub duration extended for 12.97±0.61 days. Larval survival was 74.44 per cent, followed by a pre-pupal period of 1.05±0.18 days and pupal duration of 5.93±0.86 days. Total grubs and pupal period were computed to be 18.90 ± 1.16 days with adult emergence 77.22 per cent. Total developmental period, from egg to adult was 23.45±1.20 days. Adult became darker in colour and have seven spots, three on each wing and one in the middle, near the head and act as predator to control mustard aphid. Females of beetle survived longer than the males with ovipositional period of 23.10 days and preponderance of female has been noticed with female: male ratio of 1.62: 1 in the study.

Combined Analysis of Metabolomics and Transcriptome Revealed the Effect of Bacillus thuringiensis on the 5th Instar Larvae of Dendrolimus kikuchii Matsumura.

Dendrolimus kikuchii Matsumura (D. kikuchii) is a serious pest of coniferous trees. Bacillus thuringiensis (Bt) has been widely studied and applied as a biological control agent for a variety of pests. Here, we found that the mortality rate of D. kikuchii larvae after being fed Bt reached 95.33% at 24 h; the midgut membrane tissue was ulcerated and liquefied, the MDA content in the midgut tissue decreased and the SOD, CAT and GPx enzyme activities increased, indicating that Bt has toxic effects on D. kikuchii larvae. In addition, transmission electron microscopy showed that Bt infection caused severe deformation of the nucleus of the midgut tissue of D. kikuchii larvae, vacuoles in the nucleolus, swelling and shedding of microvilli, severe degradation of mitochondria and endoplasmic reticulum and decreased number. Surprisingly, metabolomics and transcriptome association analysis revealed that four metabolic-related signaling pathways, Nicotinate and nicotinamide metabolism, Longevity regulating pathway-worm, Vitamin digestion and absorption and Lysine degradation, were co-annotated in larvae. More surprisingly, Niacinamide was a common differential metabolite in the first three signaling pathways, and both Niacinamide and L-2-Aminoadipic acid were reduced. The differentially expressed genes involved in the four signaling pathways, including NNT, ALDH, PNLIP, SETMAR, GST and RNASEK, were significantly down-regulated, but only SLC23A1 gene expression was up-regulated. Our results illustrate the effects of Bt on the 5th instar larvae of D. kikuchii at the tissue, cell and molecular levels, and provide theoretical support for the study of Bt as a new biological control agent for D. kikuchii.

Comparison of distinct gut bacterial communities in different stage of prediapause and nondiapause larvae in Loxostege sticticalis.

Symbiotic microorganisms in insects regulate multiple physiological functions, widely participating in nutrient metabolism, immune regulation, and crucial regulatory roles in development. However, little is known about how microbial factors might respond to the preparation of insect diapause. The gut bacterial communities of Loxostege sticticalis larvae induced at different photoperiod of long (LD16:8, nondiapause) and short (LD12:12, prediapause) daylength were compared, by 16S rRNA Illumina MiSeq. A total number of 42 phylum, 78 classes, 191 orders, 286 families, 495 genera, and 424 species were identified in the intestinal bacterial community of L. sticticalis larvae. Alpha diversity and beta diversity analyses revealed significant differences between nondiapause and prediapause larvae. In non-diapause larvae, the dominant intestinal bacteria were Firmicutes and Proteobacteria. In specific, in 3rd and 4th instar larvae, the main intestinal bacteria were Staphylococcus, while in 5th instar, it was JC017. For the prediapause larvae, the dominant phylum in 3rd instar larvae was Firmicutes, with the dominant genus of Staphylococcus, while in 4th and 5th instar larvae was Bacteroidota, with the dominant genus 4th instar was Staphylococcus, and in 5th instar was JC017. KEGG functional prediction analysis revealed that functional bacterial groups involved in metabolism had the highest abundance values. Specifically, the amino acid metabolism of metabolism-related functional genes in the 3rd instar prediapause larvae was significantly lower than that in the 4th and 5th instar prediapause larvae and the non-diapause treatment. However, the carbohydrate metabolism in 3rd instar prediapause larvae was significantly higher than that in 4th and 5th instar prediapause larvae and non-diapause treatments. The dominant bacterial phylum in the prediapause larvae at different stages of L. sticticalis was varied, and there were significant differences in community diversity and richness. These results suggest a complex interaction between the hosts' physiological state and its gut microbiota, indicating that bacterial communities may assist insects in adapting to diapause preparation by regulating their metabolic levels. This study lays the foundation for further understanding the physiological mechanisms by which intestinal microorganisms regulate overwintering dormancy in the L. sticticalis.

Efficacy and Residual Analysis of Three Insecticides against Spodoptera littoralis (Boisd.) on Field-grown Tomatoes

Spodoptera littoralis (Boisd.) is among the most destructive insect pests in Egypt, the field study was conducted at El-Beheira Governorate, Egypt to evaluate the toxicity of three insecticides against 2nd and 4th larval instars of these insect and residual effect in tomato fruit into open field application. The outcomes demonstrated that spinosad, methoxyfenzide and diflubenzuron proved to be very toxic. Semi-field application showed that spinosad was the most effective with 91.38 % and 100% insect pest mortalities at initial and residual effects against second instar larvae, respectively. The initial effect manifested higher morality (90.25%) for fourth instar larvae when treated with diflubenzuron followed by spinosad (86.50%), then methoxyfenzide (84.25%), while the residual effects of all tested insecticides were 100% mortality. The findings additionally demonstrated that the pre-harvest intervals (PHI) for diflubenzuron, spinosad, and methoxyfenzide were 3,7 and 10 days, respectively, for tomato fruits. Following this PHI, the products are considered safe for export and local consumption, as the residue level satisfies the maximum residue limit, which is the level documented by the European Union.

Predatory potential of Coccinella undecimpunctata L. (Coleoptera, Coccinellidae) on Aphis craccivora Koch. (Hemiptera, Aphididae) in Ladakh, India

Predatory potential of all instar larvae and adults of Coccinella undecimpunctata (Coleoptera, Coccinellidae), using Aphis craccivora Koch (Hemiptera, Aphididae) was assessed in laboratory settings. The study, conducted with varying aphid densities in rearing jars, showed a significant increase in prey consumption as aphid density rose. Furthermore, prey consumption heightened with larval development, with 4th instars devouring more aphids compared to earlier instars. Female adults exhibited greater aphid consumption than males. Deploying both 4th instar larvae and adults could enhance pest suppression.