Journal of Pest Science最新文献

Spodoptera frugiperda is a major pest in corn crops, causing significant productivity losses and exhibiting high resistance to synthetic insecticides. Essential oils (EOs) are natural substances known for their insecticidal activity against various agricultural pests. This study describes the chemical composition and bioactivity of Drimys brasiliensis EO against S. frugiperda larvae. The EO was extracted using the steam distillation method in a vat, and its chemical composition was determined using gas chromatography coupled with mass spectrometry (GC–MS). The insecticidal activity of this EO was assessed by the contact method to estimate the lethal concentration (LC₅₀ and LC₉₀) and to evaluate the effects on biochemical markers, including glutathione S-transferase (GST), esterase-α (EST-α), esterase-β (EST-β), superoxide dismutase (SOD), acetylcholinesterase (AChE) and lipid peroxidation (LPO), in 3rd instar larvae of S. frugiperda. Twenty-nine compounds were identified by GC–MS, accounting for 81.32% of the total chemical composition D. brasiliensis EO resulted in 100% mortality of S. frugiperda larvae at a concentration of 2.5%, with LC₅₀ and LC₉₀ values of 0.90 and 1.40%, respectively. Both lethal concentrations increased AChE and LPO activity, while only LC₉₀ affected the EST-α and EST-β enzymes. Drimys brasiliensis EO exhibits insecticidal activity against S. frugiperda with neurotoxic effects, as well as cellular damage, demonstrating its potential as a control method in managing this pest in conventional and organic production methods.

Cold treatment with rigorous regulatory oversight is often mandated to manage horticultural trade-related biosecurity threats, such as invasive, cold-sensitive fruit flies (Diptera: Tephritidae). Cold treatment schedules, developed through rigorous laboratory experiments, require a set temperature and duration to ensure at least a probit 8.7 (99.99%) mortality rate, regardless of infestation likelihood. This threshold is costly to demonstrate for each pest and commodity combination and the resultant treatment may be harmful to fruit quality. Moreover, these stringent schedules do not account for cold-induced mortality already occurring in commercial supply chains. We developed a predictive temperature-dependent mortality function using 28 published cold treatment studies of pest fly species to support more flexible and proportionate use of cold treatment. The daily mortality rate was unaffected by the duration of cold exposure (0–20 days). The mortality rate varied primarily by pest species (10 species) and developmental stage (eggs and larval stages), and to a lesser extent by temperature (0–7 °C) and host (13 fruit types). Our model mostly predicted fewer days to meet probit 9.0 mortality compared to empirical results from large-scale studies, suggesting these studies can be overly conservative. By leveraging previous empirical studies, our model enables estimation of temperature-dependent daily mortality for unstudied pest developmental stage host–temperature combinations, which can then be empirically validated through targeted studies. It is hoped these results will shift cold treatment usage from highly regulated, fixed temperature treatments with a target mortality rate requirement to a more flexible approach that accounts for existing commercial supply chain practices and infestation likelihood in produce.

Single-cell RNA sequencing (scRNA-seq) has emerged as a powerful tool for studying complex cellular composition and gene expression dynamics of biological systems. In this study, we analyzed the midgut of the fall armyworm (FAW), Spodoptera frugiperda, utilizing scRNA-seq technology. scRNA-seq analysis yielded high-quality sequencing data from two replicates, showcasing robust sequencing integrity, mapping efficiency, and reproducibility. We identified twelve clusters of midgut cells, including enterocytes, enteroblasts, enteroendocrine cells, goblet cells, and stem cells, each with unique marker gene expression indicative of their specialized functions. Further analysis revealed intricate gene expression profiles and enriched biological pathways associated with each cell type, shedding light on the molecular mechanisms underlying midgut function. Additionally, lineage trajectory analysis identified the differentiation pathways of midgut cell populations, confirming canonical relationships among stem cells, enteroblasts, enterocytes, and goblet cells. Furthermore, we also studied the expression of genes coding for insecticide target sites and metabolizing enzymes in different midgut cell types. Overall, our studies provide a comprehensive understanding of midgut cellular diversity and gene expression dynamics in the FAW, offering valuable information that could be used to develop methods for managing this and other pests.

Plant secondary metabolites are crucial in affecting the interactions between insect herbivores and entomoviruses. However, there is limited knowledge regarding the impact of such metabolites on the susceptibility of insect herbivores to entomoviruses. In this study, we adopted the allicin, caterpillars (Spodoptera exigua) and nucleopolyhedrovirus (SeMNPV) as a system, and found that allicin significantly increased the mortality of S. exigua larvae infected with SeMNPV by 36.03–59.45% when infected with the virus at a concentration of 2.12 × 10³ OB·mL⁻¹. Furthermore, NPV-infected larvae together treated with allicin inhibited the growth and development of larvae, comparing to individual NPV-infected larvae. Notably, we observed a significant enrichment of differentially expressed genes involved in the cytochrome P450-mediated metabolism pathway between the NPV-infected and allicin combined with NPV-treated groups. The silencing of CYP340AA1 through RNA interference significantly increased the mortality of larvae infected with SeMNPV. This investigation indicates that allicin might be a potential candidate for improving the performance of the NPV against insect herbivores and identifies that CYP340AA1 gene is important in this process.

Diaphorina citri is the vector of “Candidatus Liberibacter asiaticus” (CLas), a bacterium associated with the citrus disease known as Huanglongbing (HLB). Previous mitochondrial genome (i.e. mitogenome) population analyses revealed the prevalence of two major mitochondrial groups (MGs) of D. citri in China, separated by elevation gradients. We assessed the population diversity of D. citri from 54 major citrus-producing areas within 11 provinces/regions of China. Additionally, endosymbiont genomes were assembled for “Ca. Carsonella ruddii” (CaCr) and “Ca. Profftella armatura” (CaPa) from next-generation sequencing of 31 new Chinese samples. Most of the D. citri diversity came from single nucleotide polymorphisms (SNPs) within five mitochondrial genes: nad3, cox2, rrnL, cob, and atp6. Nine SNPs clustered the analyzed D. citri mitogenomes into three major MGs comprising seven subgroups. Independent phylogenetic trees were generated for the endosymbionts CaCr and CaPa, and a CaPa plasmid, supporting the patterns obtained for D. citri mitogenomes while adding complexity layers. Genomic data from CaCr, CaPa, along with the plasmids from CaPa contribute to the genetic diversity—consisting of 68 SNPs and two genomic gaps—reproducing phylogenetic structures outlined by previous mitochondrial genomic studies. Additionally, both the mitogenomes and the endosymbiont genomes revealed subgroups within the original MG clusters, based on further 154 SNPs and 17 gaps. Thus, the combined genomic approach reveals further aspects about population diversity and natural history of this invasive species. Further understanding of D. citri and its endosymbionts can, therefore, aid D. citri HLB management protocols and help forecast territorial expansion events.

Since 2018, increased infestation by the fall armyworm Spodoptera frugiperda (FAW), an invasive pest worldwide, has negatively affected Asian crop production. Seasonal migratory activities drive regional outbreaks of this pest, but it remains unclear whether there is direct transboundary movement between East Asian and South Asian regions. From 2019 to 2023, FAW moth movements were monitored in Ruili of Yunnan Province, a city at the border area of China and Myanmar which is located in the insect migratory route between China and South Asian countries such as India and Bangladesh. The results showed that there was regular seasonal migratory activity of the pest, which could be divided into spring–summer (April–June) and autumn (October) peak migration periods. Further analysis using trajectory simulation model indicated that the FAW moths in spring–summer migration mostly come from Myanmar, the northeastern states of India and Bangladesh, and returns to the three countries in autumn from Southwest China. Our study clarifies the regional migration pattern of the FAW moth in China and South-Southeast Asia, providing a theoretical basis for constructing a regional early warning and management systems of this pest.

The stink bugs Edessa meditabunda, Piezodorus guildinii, and Diceraeus furcatus (Hemiptera: Pentatomidae) are major pests in the Argentinean core area of soybean production. A detailed molecular genetics comprehension of how these insects perceive odorants and respond to semiochemicals and how they detoxify chemical pesticides and plant compounds are essential to improve their management strategies. We first assembled and compared the transcriptomes from E. meditabunda, P. guildinii, and D. furcatus. Regarding sequence similarity, P. guildinii and D. furcatus are closer to each other than E. meditabunda. Then, we characterized the multigene families of odorant binding proteins (OBPs) and cytochrome P450 monooxygenases (CYP). A total of 29, 38, and 39 unigenes encoding for OBP were obtained in E. meditabunda, P. guildinii, and D. furcatus, respectively, divided into classical OBPs and plus-C OBPs. A total of 72, 63, and 76 unigenes encoding for CYP were found in E. meditabunda, P. guildinii, and D. furcatus, respectively, which were further classified into 24 families and 47 subfamilies. On the other hand, we performed for the first time RNA interference in vivo by dsRNA injection in E. meditabunda, suggesting that this molecular tool can be exploited in future physiological and functional studies in this species.

Since the 1990s, the cryptic whitefly (Bemisia tabaci) has been linked to severe viral disease pandemics affecting cassava, a crucial staple crop in eastern Africa. This surge in whitefly populations has also been observed in other crops and uncultivated plants. While previous surveys have connected the increase on cassava to two specific populations, SSA1 and SSA2, the dynamics behind the population growth on other plants remain unclear. Additionally, other B. tabaci species, including EA1, IO, MED, SSA9, and SSA10, have been found on cassava in smaller numbers. This study aimed to identify the host plants that support the growth and development of different B. tabaci in Uganda by collecting fourth-instar nymphs from cassava and 20 other common host plants. Host transfer experiments were conducted to test the ability of seven species (EA1, MEAM1, MED-Africa Silver Leafing (ASL), SSA1-subgroup1, SSA1-Hoslundia, SSA6, and SSA12) to develop on cassava. The identities of the nymphs were determined using partial mitochondrial cytochrome oxidase 1 sequences. Twelve B. tabaci species were identified, including two novel species, based on the 3.5% nucleotide sequence divergence. Cassava was colonised by SSA1-SG1, SSA1-SG2, and SSA2. The most prevalent species were SSA1-SG1, MED-ASL, and SSA13, which were also the most polyphagous, colonising multiple plant species. Several whitefly species colonised specific weeds, such as Aspilia africana and Commelina benghalensis. The polyphagous nature of these species supports continuous habitats and virus reservoirs. Effective management of whitefly populations in eastern Africa requires an integrated approach that considers their polyphagy and the environmental factors sustaining host plants.

The Varroa destructor mite causes severe losses of Apis mellifera colonies, requiring recurring treatments. One such treatment is oxalic acid (OA), considered ecological. However, it is unclear whether OA affects the honey bee gut microbiota or other hive-associated microbiotas. Herein, we studied the effect of three OA treatments (trickling at 2.1% or 4.2%, and sublimation through Varrox®) upon microbial communities associated with workers’ gut, hive bee bread and pupae, sampled from conventionally or ecologically managed colonies under different anthropization levels (located in urban, rural or mountainous landscapes). We hypothesized that treatment with OA would impact the diversity and composition of bacteria and/or eukaryotic communities, and that the effect would be dose-dependent and specific to the beehive niche. Results showed that the microbiomes of apiaries under different anthropization levels and management strategies differed prior to OA application. Neither the bacterial nor the fungal communities of bee bread and pupae shifted due to OA treatment. Independent of the dosage and the application method (trickling or sublimation), OA induced slight compositional changes in the bacterial profiles of honeybee guts. Those changes were stronger the higher the anthropization (in colonies from urban areas under conventional management). OA treatment reduced the relative abundance of several pathogens, such as Nosema ceranae, and decreased the overall bacterial diversity down to values found in less anthropized colonies. Thus, our results suggest that, aside from managing Varroa infestations, OA could have beneficial effects for stressed colonies while not impairing honey bee resilience from a microbial point of view.

The activity of Cinnamomum cassia essential oil (EO) and (E)-cinnamaldehyde was investigated on the phytoparasitic species Meloidogyne incognita, Globodera rostochiensis, and Xiphinema index. Juveniles (J2) or eggs of M. incognita and G. rostochiensis and mixed-age specimens of X. index were exposed to 12.5–100 µg mL⁻¹ concentrations of the two products. The suppressiveness of soil treatments with 100–800 mg kg⁻¹ soil rates of the C. cassia EO and (E)-cinnamaldehyde to M. incognita and G. rostochiensis was assessed on potted tomato and potato, respectively. A 24-h exposure to a 12.5 µg mL⁻¹ solution of (E)-cinnamaldehyde resulted in more than 68% mortality of M. incognita J2, while a poor mortality occurred at the same concentration of the whole EO. The mortality of G. rostochiensis J2 ranged 39 and 42%, respectively, since after a 4-h exposure to a 12.5 µg mL⁻¹ solution of both products. All the X. index specimens died after a 48- and 8-h exposure to a 100 µg mL⁻¹ solution of the EO and (E)-cinnamaldehyde, respectively. Egg hatch was reduced by more than 90% after exposing the M incognita egg masses or the G. rostochiensis cysts to 800 µg mL⁻¹ concentration of both EO and (E)-cinnamaldehyde for 24 and 96 h, respectively. The infestation of M. incognita and G. rostochiensis on tomato and potato, respectively, was significantly reduced by all soil treatments with both products, though (E)-cinnamaldehyde generally resulted more suppressive than the whole EO to both nematode species. According to these results, C. cassia EO and (E)-cinnamaldehyde could be suggested as a potential source of new environment-friendly nematicides.