Agricultural Insect Pests Research Articles

RNAi FOR THE MANAGEMENT OF INSECT PESTS: A REVIEW

RNA interference (RNAi) is a biological mechanism that involves the inhibition of gene expression by the introduction of double-stranded RNA (dsRNA) molecules that are complementary to specific target genes. This technique has emerged as a promising strategy for the management of insect pests in crops. The application of RNAi to insect pest management involves the use of dsRNA molecules that are specific to essential genes in the target insect species. When these dsRNA molecules are ingested by the pests, they trigger a silencing mechanism that inhibits the expression of the target genes, leading to reduced pest populations and damage to crops. RNAi-based insect pest management has several advantages over traditional chemical-based methods, including its specificity, effectiveness, and environmental safety. However, there are still some challenges associated with the use of RNAi, such as the potential for offtarget effects and the need for effective delivery methods. Nonetheless, RNAi technology holds great promise for sustainable and effective management of insect pests in agriculture.

Climate and pest interactions pose a cross-landscape management challenge to soil and water conservation

Climate change and biological invasions by plant pests (weeds), agriculture and forest insect pests (insects), and microbial pests (plant pathogens) are complex interactive components of global environmental change. The influence of pest distribution and prevalence across landscapes are challenging the conservation and sustainability of natural resources, agricultural production, native biological diversity, and the valuable ecosystem services they provide (Huenneke 1997; Vitousek 1997; Juroszek and von Tiedemann 2013; Ziska and Dukes 2014). Since 2000, numerous scientific studies indicate accelerating climate change is posing substantial risks to natural and managed systems in North America (IPPC 2022). Intensified droughts, large-scale wildfires, and increased demands for limited surface and groundwater water supplies in arid regions are threatening the sustainability of irrigated agriculture and contributing to economic losses (Stewart et al. 2020), while extreme rainfall events are contributing to severe riverine and urban flooding across the United States. Climate change affects crops, rangelands, forests, and natural areas directly through the immediate effects of temperature, precipitation, and atmospheric carbon dioxide (CO₂) levels and thereby impacts production and management systems. These effects are amplified by climate-driven increases in weed, insect, and plant pathogen problems that further complicate related factors such as water, nutrient, and pest management (Walthall et al. 2013). Changing climates also alter physiological, ecological, and evolutionary processes that can support increased establishment, invasiveness, local spread, and geographic range changes of weeds, insects, and plant pathogens (Chidawanyika et al. 2019; Gallego-Tevár et al. 2019; Ziska et al. 2019) that have cascading effects on soil and water quality, and human livelihoods. Thus, a need exists for cross-habitat and landscape/watershed-scale perspectives to improve understanding of mechanisms underlying pest fitness and impacts within and across integrated systems.

Plasticity in oviposition and foraging behavior in the invasive pest Drosophila suzukii across natural and agricultural landscapes.

The effects and extent of the impacts of agricultural insect pests in and around cropping systems is a rich field of study. However, little research exists on the presence and consequence of pest insects in undisturbed landscapes distant from crop hosts. Research in such areas may yield novel or key insights on pest behavior or ecology that is not evident from agroecosystem-based studies. Using the invasive fruit pest Drosophila suzukii (Matsumura) as a case study, we investigated the presence and resource use patterns of this agricultural pest in wild blackberries growing within the southern Appalachian Mountain range of North Carolina over 2 years. We found D.suzukii throughout the sampled range with higher levels of infestation (D.suzukii eggs/g fruit) in all ripeness stages in natural areas when compared with cultivated blackberry samples, but especially in under-ripe fruit. We also explored a direct comparison of oviposition preference between wild and cultivated fruit and found higher oviposition in wild berries when equal weights of fruit were offered, but oviposition was higher in cultivated berries when fruit number was equal. Forest populations laid more eggs in unripe wild-grown blackberries throughout the year than populations infesting cultivated berries. This suggests D.suzukii may change its oviposition and foraging behavior in relation to fruit type. Additionally, as D.suzukii exploits a common forest fruit prior to ripeness, further research is needed to explore how this affects wild food web dynamics and spillover to regional agroecosystems.

Current Scenario of Exogenously Induced RNAi for Lepidopteran Agricultural Pest Control: From dsRNA Design to Topical Application.

Invasive insects cost the global economy around USD 70 billion per year. Moreover, increasing agricultural insect pests raise concerns about global food security constraining and infestation rising after climate changes. Current agricultural pest management largely relies on plant breeding-with or without transgenes-and chemical pesticides. Both approaches face serious technological obsolescence in the field due to plant resistance breakdown or development of insecticide resistance. The need for new modes of action (MoA) for managing crop health is growing each year, driven by market demands to reduce economic losses and by consumer demand for phytosanitary measures. The disabling of pest genes through sequence-specific expression silencing is a promising tool in the development of environmentally-friendly and safe biopesticides. The specificity conferred by long dsRNA-base solutions helps minimize effects on off-target genes in the insect pest genome and the target gene in non-target organisms (NTOs). In this review, we summarize the status of gene silencing by RNA interference (RNAi) for agricultural control. More specifically, we focus on the engineering, development and application of gene silencing to control Lepidoptera through non-transforming dsRNA technologies. Despite some delivery and stability drawbacks of topical applications, we reviewed works showing convincing proof-of-concept results that point to innovative solutions. Considerations about the regulation of the ongoing research on dsRNA-based pesticides to produce commercialized products for exogenous application are discussed. Academic and industry initiatives have revealed a worthy effort to control Lepidoptera pests with this new mode of action, which provides more sustainable and reliable technologies for field management. New data on the genomics of this taxon may contribute to a future customized target gene portfolio. As a case study, we illustrate how dsRNA and associated methodologies could be applied to control an important lepidopteran coffee pest.

The evolutionary process of invasion in the fall armyworm (Spodoptera frugiperda)

The fall armyworm (FAW; Spodoptera frugiperda) is one of the major agricultural pest insects. FAW is native to the Americas, and its invasion was first reported in West Africa in 2016. Then it quickly spread through Africa, Asia, and Oceania, becoming one of the main threats to corn production. We analyzed whole genome sequences of 177 FAW individuals from 12 locations on four continents to infer evolutionary processes of invasion. Principal component analysis from the TPI gene and whole genome sequences shows that invasive FAW populations originated from the corn strain. Ancestry coefficient and phylogenetic analyses from the nuclear genome indicate that invasive populations are derived from a single ancestry, distinct from native populations, while the mitochondrial phylogenetic tree supports the hypothesis of multiple introductions. Adaptive evolution specific to invasive populations was observed in detoxification, chemosensory, and digestion genes. We concluded that extant invasive FAW populations originated from the corn strain with potential contributions of adaptive evolution.

Direct and Endophytic Effects of Fungal Entomopathogens for Sustainable Aphid Control: A Review

Entomopathogenic fungi (EPF) are cosmopolitan species of great interest in pest management due to their ability to cause epizooty in soil-dwelling and aboveground insects. Besides their direct effect against a wide host range of serious agricultural insect pests, such as aphids, a major emphasis has been placed on investigating the impact of EPF with endophytic traits (EIPF) on aboveground tripartite interactions between host plants, herbivores and beneficial insects. However, despite their valuable role in biocontrol processes, there is still more to explore about their diverse potential as ecofriendly biological control agents. Herein, we provide an overview of the meaningful role and faced challenges following the use of EPF and EIPF to control aphids.

Plant-mediated rifampicin treatment of Bemisia tabaci disrupts but does not eliminate endosymbionts

Whiteflies are among the most important global insect pests in agriculture; their sustainable control has proven challenging and new methods are needed. Bacterial symbionts of whiteflies are poorly understood potential target of novel whitefly control methods. Whiteflies harbour an obligatory bacterium, Candidatus Portiera aleyrodidarum, and a diverse set of facultative bacterial endosymbionts. Function of facultative microbial community is poorly understood largely due to the difficulty in their selective elimination without removal of the primary endosymbiont. Since the discovery of secondary endosymbionts, antibiotic rifampicin has emerged as the most used tool for their manipulation. Its effectiveness is however much less clear, with contrasting reports on its effects on the endosymbiont community. The present study builds upon most recent method of rifampicin application in whiteflies and evaluates its ability to eliminate obligatory Portiera and two facultative endosymbionts (Rickettsia and Arsenophnus). Our results show that rifampicin reduces but does not eliminate any of the three endosymbionts. Additionally, rifampicin causes direct negative effect on whiteflies, likely by disrupting mitochondria. Taken together, results signify the end of a rifampicin era in whitefly endosymbiont studies. Finally, we propose refinement of current quantification and data analysis methods which yields additional insights in cellular metabolic scaling.

RNAi-mediated knockdown of arginine kinase genes leads to high mortality and negatively affect reproduction and blood-feeding behavior of Culex pipiens pallens.

Arginine kinase (AK) is one of the crucial enzymes involved in energy metabolism in invertebrates, and has been proposed as the target for RNA interference (RNAi)-based control of agricultural insect pests. While there is only one AK gene in most insects, two AK genes were identified in Culex pipiens pallens, the primary vector of lymphatic filariasis and epidemic encephalitis. The full-length cDNA sequences of CpAK1 and CpAK2 genes were obtained by reverse transcription PCR(RT-PCR) and rapid amplification of cDNA ends (RACE). The expression levels of CpAK1 and CpAK2 in different developmental stages and tissues were detected by reverse transcription quantitative PCR (RT-qPCR). The role of CpAK1 and CpAK2 in the reproduction and blood feeding behavior was analyzed using RNA interference (RNAi). Full-length cDNAs of CpAK1 and CpAK2 were isolated from Cx. pipiens pallens. Analysis of the expression pattern revealed that the mRNA level of CpAK1 was significantly higher than CpAK2 in all development stages and tissues examined, and the expressions of both CpAK1 and CpAK2 were upregulated in response to blood feeding. The co-knockdown of CpAK1 and CpAK2 mediated by RNAi led to high mortality (74.3%) of adult female mosquitoes and decreased hatchability (59.9%). Remarkably, the blood feeding rate and the engorgement rate of the female mosquitoes were negatively affected by co-injection of dsRNAs targeting CpAK1 and CpAK2. CpAK1 and CpAK2 were detected in all developmental stages and tissues, but showed divergence in expression level. RNAi-mediated knockdown of AK genes leads to high mortality and negatively affect blood-feeding behavior of Cx. pipiens pallens, suggesting that AK could be used for the target of RNAi-based mosquito control in the future.

Diallyl trisulfide reduced the reproductive capacity of male Sitotroga cerealella via the regulation of juvenile and ecdysone hormones

Environmental pollution and resistance in animals are major concerns for the application of synthetic pesticides. Diallyl trisulfide (DAT), an active compound in garlic essential oil, is a novel tool for active and safe control of agricultural insect pests. In this study, we analysed the effects of DAT (0.01 μL/L) on the protein content in male reproductive tissues (accessory glands, ejaculatory ducts, and testis), and juvenile hormone (JH) and ecdysone titres in a highly detrimental pest of stored products, Sitotroga cerealella. Evaluation of the expression profile of JH and ecdysone pathway-related genes in various tissues indicated that the accessory gland protein and ecdysone titres were markedly decreased after DAT fumigation, whereas the testis protein content and JH titre were increased. However, the protein content of the ejaculatory ducts remained unchanged between the treated and control groups. Further investigation revealed that DAT disrupted the mRNA expression of key enzymes involved in JH and ecdysone pathways. While increased mRNA levels of juvenile hormone acid O-methyltransferase (JHMAT) and Kruppel homologue 1 (Kr-h1) were observed after 4 and 7 h of DAT fumigation, the levels of juvenile hormone epoxide hydrolase (JHEH) were substantially reduced 3 h post-fumigation. mRNA levels of the ecdysone-responsive gene, FTZF1, and cytochrome P450 enzyme, CYP315A1, were notably decreased at 7 h and 4 h, respectively, post-fumigation, whereas CYP314A1 and CYP302A1 mRNA levels decreased after 3 h and 4 h, respectively. While DAT fumigation disrupted sperm number in the testis, ejaculatory ducts, and seminal vesicles, topical application of the 20-hydroxyecdysone (20E) analogue also lowered sperm number in the ejaculatory ducts. Topical application of methoprene, a JH analogue, increased the protein content in the testes, but not in the accessory glands or ejaculatory ducts. However, the survival rate was not affected by the topical application of methoprene or 20E. These data suggest that DAT regulates JH and ecdysone via its molecular pathway genes and modulates endocrine secretion during the male reproductive process.

New classes of insecticides with a unique mode of action for the management of insect pests in agriculture and horticulture crops – A review

New classes of insecticides with a unique mode of action for the management of insect pests in agriculture and horticulture crops – A review

Environmental effects of harvesting some Mexican wild edible insects: An overview

Most traditional edible insects are collected from the forest and agricultural fields, where they are considered pests. However, their importance goes beyond this. They also have an ecological role and potential to be an emerging alternative source of high-quality nutrients that can help satisfy the growing food demand for the human population. Agricultural insect pests are a healthy food source during the harvesting season in many tropical countries. In Mexico, wild insects such as chicatana (queen of flying leaf-cutter ant, Atta mexicana Smith, 1,858; Hymenoptera: Formicidae), chapulín (grasshopper, Pyrgomorphidae), chinicuil (agave red worm, Comadia redtenbacheri Hammerschmidt, 1,848: Lepidoptera, Cossidae), and meocuil (agave white worm, Aegiale hesperiaris Walker 1,856, Lepidoptera, Hesperiidae) are seasonally collected from the agricultural land and forest for food and medicine. Thus, their consumption might be regarded as support for biological plague control. However, in most countries (Mexico included), there is a lack of legislation about edible insects from harvesting to sacrifice and even their main safety aspects. So then, this research aims to provide an updated assessment of the potential use of agricultural pest insects as a sustainable alternative for food, considering current international legislative and ethical concerns about harvesting and consuming wild edible insects, focusing on some of the wild edible pest insects in Mexico.

Insecticidal Activities and GC-MS Analysis of the Selected Family Members of Meliaceae Used Traditionally as Insecticides.

The environmental and health risks associated with synthetic pesticides have increased the demand for botanical insecticides as safer and biodegradable alternatives to control insect pests in agriculture. Hence in this study, five Meliaceae species were evaluated for their insecticidal activities against the Spodoptera frugiperda and the Plutella xylostella larvae, as well as their chemical constituents. Repellence, feeding deterrence, and topical application bioassays were employed to evaluate their insecticidal activities. GC-MS analysis was performed to identify chemical compounds present in each plant. The repellence bioassay indicated that Melia azedarach extracts exhibited the highest repellence percentage against S. frugiperda (95%) and P. xylostella (90%). The feeding deterrence bioassay showed that M. azedarach and Trichilia dregeana extracts displayed excellent antifeeding activity against the S. frugiperda (deterrent coefficient, 83.95) and P. xylostella (deterrent coefficient, 112.25), respectively. The topical application bioassay demonstrated that Ekebergia capensis extracts had the highest larval mortality against S. frugiperda (LD50 0.14 mg/kg). Conversely, M. azedarach extracts showed the highest larval mortality against P. xylostella (LD50 0.14 mg/kg). GC-MS analysis revealed that all plant extracts had compounds belonging to the two noteworthy groups (phenols and terpenes), which possess insecticidal properties. Overall, this study lends scientific credence to the folkloric use of Meliaceae species as potential biocontrol agents against insect pests.

Comparison of Iflavirus Diversity in Agricultural and Forest Pest Lepidoptera

Iflaviridae is a novel and important family of viruses in the Picornavirales order that infects invertebrates. Iflaviruses are non-enveloped, linear, positive single-stranded RNA viruses. The importance of iflaviruses in agriculture and forestry is twofold because these viruses, both cause economic loss by making insects such as honey bees and silkworms ill and prevent economic loss by making agricultural and forest pest insects ill. Therefore, iflaviruses contain highly interesting isolates that infect both beneficial and harmful insects in agriculture. Its genome structure, like most RNA viruses, has a very small genome size (8.8-10 kb), with a single open reading frame in the entire genome. The genomes of 14 infective iflaviruses that infect agricultural and forest pest insects from different countries have been analyzed so far. In this study, the similar relationship between these 14 viruses, whose complete genomes are available, was analyzed according to the complete sequence of the polyprotein. The results showed that the virus isolates obtained from forest pest insects were closely related to each other. Similarly, it was revealed that the iflaviruses obtained from insects that damage agricultural products are more similar to each other. In addition, the results from this study support previous studies on adding a new genus to the Iflaviridae family, which has only one genus.

Comparative Biology of Spodoptera litura (Lepidoptera: Noctuidae) on Different Hosts under Laboratory Conditions in Pakistan

One of the most economically significant insect pests in world agriculture is the armyworm, Spodoptera litura Fabricius (Lepidoptera; Noctuidae). In 2019, S. litura was reared in a lab environment to study its biological parameters on different hosts. The sixth larval instar was recorded in this study. The period of 1st, 2nd, 3rd, 4th, 5th and 6th larval instar on cotton was 3.55±0.10, 3.59±0.09, 3.99±0.10, 4.56±0.09, 6.65±0.15, and 5.59±0.17 days, respectively. Maximum adult emergence was recorded on cabbage followed by cotton and maize. The larval length and weight were found higher on cabbage followed by cotton and maize. The pupal development was less concerning days on maize than other tested hosts. The highest mean fecundity was 2954.16 eggs per female on cabbage leaves while minimum with 987.19 eggs per female on maize leaves. The sex ratio of female to male was recorded as 1:0.7, 1:0.6, and 1:0.5, on cabbage, cotton and maize, respectively. Female was long lived than male as recorded on all tested hosts. Among all tested hosts, cabbage was recorded as the most preferable and suitable host for pest. The current study findings will provide suitable information about hosts of S. litura but suggest further studies.

Bioefficacy of isolated compound l-isoleucine, N-allyloxycarbonyl-, and dodecyl ester from entomopathogenic actinobacteria Actinokineospora fastidiosa against agricultural insectpests, human vectormosquitoes, and antioxidant activities.

Spodoptera litura and Helicoverpa armigera are polyphagous pests of agricultural crops in the Asian tropics since these pests have been responsible for massive crop and carry economic losses and low commodity production. At the same time, mosquitoes are vectors for numerous dreadful diseases, which is the most important group of insect for their public health concern. Using synthetic insecticides to control the pests can lead to contamination of land surface and groundwater and impact beneficial soil organisms and nontarget species. Applications of bioactive compounds are received considerable attention across the world as alternatives to synthetic insecticides. In the current study, actinobacterial secondary metabolite was isolated from Actinokineospora fastidiosa for the first time. The effect of actinobacterial metabolite (l-isoleucine, N-allyloxycarbonyl-, and dodecyl ester) was assessed on agricultural pest S. litura and H. armigera, mosquito vectors larvae Ae. aegypti, An. stephensi, and Cx. quinquefasciatus. The bioactive fraction was characterized through UV, FTIR, and NMR analysis. GC-MS analyses reveal the existence of a bioactive compound with a respective retention time of 19.740 responsible for larvicidal activity. The bioefficacy of the l-isoleucine, N-allyloxycarbonyl-, and dodecyl ester showed high antifeedant activity on S. litura (80.80%) and H. armigera (84.49%); and larvicidal activity on S. litura (82.77%) and H. armigera (88.00%) at 25μg/mL concentration, respectively. The effective LC50 values were 8.07μg/mL (F = 2.487, r2 = 0.988, P ≤ 0.05) on S. litura and 7.53μg/mL (F = 123.25, r2 = 0.951, P ≤ 0.05) on H. armigera. The mosquito larvicidal effect of isolated compounds l-isoleucine, N-allyloxycarbonyl-, and dodecyl ester treated against Ae. aegypti, An. stephensi, and Cx. quinquefasciatus the obtained percentage mortality was 96.66, 83.24, 64.52, 50.00, and 40.00% against Ae. aegypti; 100.00, 86.22, 73.81, 65.37, and 56.24% against An. stephensi; 100.00, 90.00, 76.24, 68.75, and 56.23% against Cx. quinquefasciatus. The mosquito larvae of Ae. aegypti obtained LC50 value was 13.25μg/mL, F = 28.50, r2 = 0.90; on An. stephensi was 10.19μg/mL, F = 15.55, r2 = 0.83, and Cx. quinquefasciatus was 9.68μg/mL, F = 20.00, r2 = 0.87. Furthermore, l-isoleucine-, N-allyloxycarbonyl-, and dodecyl ester-treated larvae produced significant pupicidal activity on S. litura (62.71%) and H. armigera (66.50%) at 25μg/mL, along with increased larval and pupal duration as compared to control group. Treated larvae revealed obliteration in the midgut epithelial cells and destruction of microvilli was noticed as compared to the control. The isolated compounds l-isoleucine, N-allyloxycarbonyl-, and dodecyl ester did not produce any significant mortality on zebrafish embryos in all tested concentrations on biosafety observation. The potential microbial isolated molecule may fit well in IPM programs. Since the risk to human health, the environment, etc. is unknown.

Cross-protection interactions in insect pests: Implications for pest management in a changing climate.

Agricultural insect pests display an exceptional ability to adapt quickly to natural and anthropogenic stressors. Emerging evidence suggests that frequent and varied sources of stress play an important role in driving protective physiological responses; therefore, intensively managed agroecosystems combined with climatic shifts might be an ideal crucible for stress adaptation. Cross-protection, where responses to one stressor offers protection against another type of stressor, has been well documented in many insect species, yet the molecular and epigenetic underpinnings that drive overlapping protective responses in insect pests remain unclear. In this perspective, we discuss cross-protection mechanisms and provide an argument for its potential role in increasing tolerance to a wide range of natural and anthropogenic stressors in agricultural insect pests. By drawing from existing literature on single and multiple stressor studies, we outline the processes that facilitate cross-protective interactions, including epigenetic modifications, which are understudied in insect stress responses. Finally, we discuss the implications of cross-protection for insect pest management, focusing on the consequences of cross-protection between insecticides and elevated temperatures associated with climate change. Given the multiple ways that insect pests are intensively managed in agroecosystems, we suggest that examining the role of multiple stressors can be important in understanding the wide adaptability of agricultural insect pests. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Effects of global warming on insect behaviour in agriculture

Global warming and climate change are some of the most widely discussed topics in today's society, and they are of considerable importance to agriculture globally. Climate change directly affects agricultural production. On the other hand, the agricultural sector is inherently sensitive to climate conditions, and this has made the agricultural sector one of the most vulnerable sectors to the effects of global climate change. Rising CO2 levels in the atmosphere, increased temperature, and altering precipitation patterns all substantially influence agricultural insect pests and agricultural productivity. Climate change has a number of implications for insect pests. They can lead to a decreased biological control effectiveness, particularly natural enemies, increased incidence of insect-transmitted plant diseases, increased risk of migratory pest invasion, altered interspecific interaction, altered synchrony between plants and pests, increase in the number of generations, increased overwintering survival, and increase in geographic distribution. As a consequence, agricultural economic losses are a real possibility, as is a threat to human food and nutrition security. Global warming will necessitate sustainable management techniques to cope with the altering state of pests, as it is a primary driver of pest population dynamics. Future studies on the impacts of climate change on agricultural insect pests might be prioritized in several ways. Enhanced integrated pest control strategies, the use of modelling prediction tools, and climate and pest population monitoring are only a few examples.

Evaluation of Lethal and Sublethal Effects of Methyl Benzoate on the Generalist Predator Orius laevigatus (Fieber).

Methyl benzoate (MBe), a volatile organic molecule, has been shown to have insecticidal effects on a variety of agricultural, stored products, and urban arthropod pests in recent investigations. However, the toxicity of MBe against nontarget organisms has rarely been investigated. This study investigated the lethal and sublethal effects of MBe on the generalist predator Orius laevigatus (Fieber) (Hemiptera: Anthocoridae) via different exposure routes. This species is an important natural enemy of thrips, aphids, and mites in biological control programs globally. Acute toxicity bioassays conducted on O. laevigatus showed that the lethal median concentration (LC50) values of MBe for topical and residual toxicity were 0.73 and 0.94%, respectively, after 24 hr of exposure. Importantly, a sublethal concentration of MBe (LC30 = 0.51%) did not affect the survival and reproduction of O. laevigatus. In addition, prey consumption by O. laevigatus under different exposure conditions with varying densities of Aphis gossypii (Glover) (Hemiptera: Aphididae) adults demonstrated a good fit for a Type II functional response. The sublethal concentration of MBe did not affect the attack rate and handling time of O. laevigatus compared to untreated insects, nor did it affect the longevity and fecundity of O. laevigatus females. Thus, according to the International Organization for Biological Control, the sublethal MBe concentration for O. laevigatus is categorized as harmless and may be used in conjunction with this predator species for integrated control of many agricultural insect pests.

Characterization and Evaluation of Indigenous Bacillus thuringiensis Isolate T352 against Fall Armyworm, Spodoptera frugiperda (J.E. Smith)

Bacillus thuringiensis (Bt) Berliner is a ubiquitous soil bacterium with commercial bio pesticidal value and widely used for effective control of various important agricultural insect pests. Invasion of Fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith) into India caused potential yield loss in maize production, and also it threats the cultivation of other related crops. This study was aimed to characterize and evaluate the pathogenic activity of indigenous Bt isolate T352 against fall armyworm (FAW), S. frugiperda. The Bt isolate T352 was creamy white in colour and had irregular shaped flat colonies with undulated margin. Bipyramidal shape of parasporal inclusions was found in isolate T352. The isolate produced protein bands of ̴ 130 kDa and ̴ 65 kDa size in SDS PAGE analysis. PCR screening also confirmed the presence of cry1Ab, cry1Ac, cry2Aa, cry2Ab and vip3A genes. During probit analysis, isolate T352 exhibited the LC50 of 1.927 µg/ml as against 0.421µg/ml in positive standard strain HD- 1 based on mortality observed at 72 h after treatment in leaf disc bioassay with spore crystal mixtures.

Detecting Pests From Light-Trapping Images Based on Improved YOLOv3 Model and Instance Augmentation.

Light traps have been widely used as effective tools to monitor multiple agricultural and forest insect pests simultaneously. However, the current detection methods of pests from light trapping images have several limitations, such as exhibiting extremely imbalanced class distribution, occlusion among multiple pest targets, and inter-species similarity. To address the problems, this study proposes an improved YOLOv3 model in combination with image enhancement to better detect crop pests in real agricultural environments. First, a dataset containing nine common maize pests is constructed after an image augmentation based on image cropping. Then, a linear transformation method is proposed to optimize the anchors generated by the k-means clustering algorithm, which can improve the matching accuracy between anchors and ground truths. In addition, two residual units are added to the second residual block of the original YOLOv3 network to obtain more information about the location of the underlying small targets, and one ResNet unit is used in the feature pyramid network structure to replace two DBL(Conv+BN+LeakyReLU) structures to enhance the reuse of pest features. Experiment results show that the mAP and mRecall of our proposed method are improved by 6.3% and 4.61%, respectively, compared with the original YOLOv3. The proposed method outperforms other state-of-the-art methods (SSD, Faster-rcnn, and YOLOv4), indicating that the proposed method achieves the best detection performance, which can provide an effective model for the realization of intelligent monitoring of maize pests.