Search Results (51)

Grain protectants are insecticide formulations applied directly to raw grain to prevent and control insect infestations in bulk storage; however, their efficacy depends on insect species, commodity, and grain quality. The objective of this study was to determine the residual efficacy of four commercially available grain protectants, Gravista^® (deltamethrin + methoprene + PBO), Diacon^® IGR (methoprene), Sensat^TM (spinosad), and EverGreen^® (pyrethrin), applied to sorghum and held for 28 weeks, against Rhyzopertha dominica (F.) and Sitophilus oryzae (L.). Subsamples were collected every four weeks and infested with 10 adults of either species. Adult mortality was assessed after seven days and progeny, frass, and insect-damaged kernels were evaluated after eight weeks. Rhyzopertha dominica was more susceptible to all insecticides compared to S. oryzae, and had fewer progeny compared to control sorghum. Spinosad-treated sorghum resulted in 100% adult mortality in R. dominica compared to 30–39% in S. oryzae. There was an overall decline in kernel moisture content, which may have impacted progeny of both species in the control and insecticide-treated sorghum. These findings highlight the influence of insecticide formulation, insect species, and grain moisture content on the long-term efficacy of grain protectants applied to sorghum. Full article

The increasing prevalence of insecticide resistance threatens the efficacy of Integrated Mosquito Management (IMM) programs, particularly in regions reliant on chemical control for vector-borne disease prevention. Cross-resistance between active ingredients severely complicates essential resistance management strategies like product rotation. The previous literature suggests that laboratory-induced S-methoprene-resistant Culex species may be somewhat cross-resistant to pyriproxyfen, another juvenile hormone analog. This is a critical concern in the Chicago, IL, USA metropolitan area, where pyriproxyfen is used against mosquitoes with reduced susceptibility to S-methoprene. To determine if S-methoprene-resistant Culex pipiens are cross-resistant to pyriproxyfen in nature, we assessed 31 field-collected populations with significant S-methoprene exposure but varying histories of pyriproxyfen use by dose–response bioassays. Culex pipiens from all 31 sites exhibited high resistance to S-methoprene (RR₅₀ > 10), and 84% were at least moderately resistant to pyriproxyfen (RR₅₀ > 5). Reduced susceptibility to pyriproxyfen was confirmed in pyriproxyfen-unexposed populations, demonstrating potential S-methoprene-mediated cross-resistance. The level of S-methoprene resistance and the level of pyriproxyfen exposure significantly correlated with the level of pyriproxyfen resistance. We report the first widespread, high-level pyriproxyfen resistance in any medically significant mosquito species, underscoring the critical need for routine resistance surveillance and the adoption of integrated resistance management tactics utilizing larvicides with distinct modes of action. Full article

Understanding the genetic basis of growth and moltism in silkworm (Bombyx mori) is essential for improving silk production efficiency and elucidating the mechanisms underlying developmental plasticity. Thus, this study aimed to establish a collection of 20 representative B. mori core strains and perform integrative genomic analyses combining genome-wide association studies (GWASs) and population-specific variant detection. A total of 5,293,831 high-confidence single-nucleotide variants (SNVs) were identified across the population, and GWAS revealed significant associations between specific genetic loci and four growth-related traits: larval weight at day 7 of the fifth instar, pupal weight, cocoon weight, and cocoon layer weight. Among these, two missense variants within the Cycb gene were significantly correlated with increased body weight at the late fifth instar stage, suggesting a potential role for this isoform in regulating cell-cycle-driven tissue expansion during rapid larval growth. Moreover, a population-based comparison identified 2803 trimolter-specific missense SNVs in 1440 genes, of which 109 were functionally annotated. Notably, homozygous variants were detected in key developmental regulators, such as MET1 and TOR1, implying potential alterations in juvenile hormone signaling and nutrient-dependent growth pathways that may contribute to the dominant trimolter phenotype. Although experimental validation remains necessary, these findings provide a genomic framework for understanding the molecular mechanisms underlying moltism variation and offer valuable resources for future silkworm genetic improvement. Full article

Methyl farnesoate (MF) is a sesquiterpenoid hormone that controls a variety of physiological processes in crustaceans, including morphogenesis, development, reproduction, and molting. MF action is mediated by a transcriptional signaling cascade consisting of Methoprene-tolerant (Met), Steroid receptor coactivator (Src), Krüppel homolog 1 (Kr-h1), and Ecdysone response gene 93 (E93) transcription factors (TFs), and transcriptional co-regulators CREB-binding protein (CBP) and C-terminal-binding protein (CtBP). Phylogenetic and sequence analyses revealed that these genes were highly conserved across pancrustacean species. Met and Src were characterized as basic helix-loop-helix, Period (Per)-Aryl Hydrocarbon Nuclear Translocator (ARNT)-Single-minded (Sim) protein (bHLH-PAS) TFs; Kr-h1 was characterized as a C₂H₂ zinc finger TF with seven zinc finger motifs; E93 was characterized as a helix-turn-helix, pipsqueak (HTH_Psq) TF. CBP was identified by several zinc finger-binding regions with Transcription Adaptor Zinc Finger 1 and 2, Really Interesting New Gene, Plant homeodomain, and Z-type zinc finger domains; the Kinase-inducible Domain Interacting-transcription factor docking site; the Bromodomain-acetylated lysine recognition and binding site; the histone acetyltransferase domain; and a C-terminal CREB-binding region containing a nuclear receptor co-activator-binding domain. CtBP had a dehydrogenase domain with arginine-glutamate-histidine catalytic triad. 81 Met contigs, 45 Src contigs, 136 Kr-h1 contigs, 66 E93 contigs, 60 CBP contigs, and 172 CtBP contigs were identified across pancrustacean taxa, including decapod crustaceans. Bioinformatic identification and annotation of these TFs and co-regulators in brachyuran Y-organ (YO) transcriptomes suggests that MF signaling influences YO ecdysteroidogenesis; functional tests in the YO are needed to establish causality. Full article

Ladybird beetle, Serangium japonicum (Coleoptera: Coccinellidae), is an important predatory natural enemy of whiteflies, and its mass rearing is crucial for biological control. This study evaluated the suitability of Corcyra cephalonica (Lepidoptera: Pyralidae) eggs as an alternative diet for adult S. japonicum by directly comparing it to the natural prey, Bemisia tabaci (Hemiptera: Aleyrodidae) nymphs. Results showed that, compared to a B. tabaci diet, feeding on C. cephalonica eggs supported normal development and significantly extended the lifespan of adult S. japonicum, without compromising offspring quality (hatching rate, development, survival, or predatory capacity). However, the moth egg diet significantly impaired reproduction, causing delayed ovarian development, reduced vitellogenesis, and altered gene expression: downregulation of methoprene-tolerant, Juvenile hormone acid O-methyltransferase, Vitellogenin, and Vitellogenin receptor, and upregulation of Juvenile hormone esterase and Copper/zinc superoxide dismutase. Practically, this work defines C. cephalonica eggs as a suboptimal but viable supplementary diet for colony maintenance, but unsuitable as a sole diet for mass-rearing reproductively robust populations. Our findings explain the physiological and molecular mechanisms underlying the “reproduction–lifespan trade-off” in S. japonicum induced by feeding on C. cephalonica eggs, providing a mechanistic basis for its rational application in the mass production of natural enemies. Full article

The circadian clock is a conserved timekeeping mechanism that enables organisms to anicipate and adapt to daily environmental cycles. While its role in photoperiodic diapause has been documented, its fundamental function in maintaining reproductive and metabolic homeostasis under favorable conditions remains less explored, especially in biological control agents. This study investigates the functional roles of the core circadian clock genes Cycle (AcCyc) and Clock (AcClk) in the predatory bug Arma chinensis, focusing on their regulation of reproduction and metabolism under non-diapause conditions. We characterized these genes and analyzed their spatiotemporal expression under diapause and non-diapause conditions. Using RNA interference, we knocked down AcCyc and AcClk in non-diapausing females and evaluated phenotypic impacts on ovarian development, fecundity, and energy reserves. qPCR analyses delineated downstream effects on juvenile hormone (JH) signaling. Results showed that diapause altered AcCyc and AcClk expression rhythms. Their knockdown severely impaired reproduction, reducing ovarian size, vitellogenin expression, and egg production, while concurrently decreasing triglyceride levels indicating disrupted energy homeostasis. Mechanistically, gene silencing downregulated key JH pathway components, Methoprene-tolerant (Met) and Krueppel homolog 1 (Kr-h1). We conclude that AcCyc and AcClk are essential maintainers of reproductive–metabolic homeostasis, not merely diapause regulators. This reframes the clock’s role from a seasonal timekeeper to a central hub for daily physiological coordination, offering new insights for improving biocontrol agent production. Full article

House flies (Musca domestica L.) are major vectors of numerous pathogens affecting both humans and animals. The global distribution of house flies has been steadily increasing the expansion of human settlements, increased waste production, and the growth of livestock farms established to meet the demand for animal-derived products. Frequent exposure to intensive pesticide applications in agricultural and livestock areas has accelerated the development of insecticide resistance, posing a serious challenge to sustainable control efforts. The widespread and repeated use of conventional chemical insecticides has contributed to rapid resistance evolution in many populations worldwide. In this study, the acute toxic effects of two insect growth regulators (IGRs)—cyromazine and methoprene—commonly used in the larval stages of house flies were evaluated against adult flies. Treatments were applied (3 replicates) orally via 40% sugar-water solutions containing 1%, 5%, and 10% concentrations, and bioassays were conducted on eight distinct house fly populations. The results showed that cyromazine caused average adult mortalities of 76.35%, 81.00%, and 84.50% within 48 h, while methoprene produced 70.62%, 99.37%, and 100% mortality at the same concentrations. At 10%, methoprene achieved 100% mortality across all populations, whereas cyromazine induced mortality ranging from 44.28% to 100%. These findings suggest that IGRs can be effective alternatives to conventional insecticides and can be integrated into IPM/IVM programs to reduce chemical use and delay resistance. Full article

This systematic review and meta-analysis aims to: (1) characterize the distribution of published inhibition of emergence (IE₅₀, IE₉₀, and IE₉₅) reference values for pyriproxyfen and methoprene in Culex pipiens [L.], Aedes aegypti [L.], and Aedes albopictus [Skuse]; (2) generate combined-effect IE values using a DerSimonian and Laird (DL) random-effects model to establish benchmarks for future resistance assessments; and (3) compare these combined-effect IE values with previously published literature. A systematic search was conducted in PubMed, SciELO, J-STAGE, and Google Scholar up to 10 February 2025, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Eligible studies were primary, peer-reviewed literature that aligned with World Health Organization (WHO) protocols for insect growth regulator (IGR) resistance testing, specifically those reporting susceptible reference IE values from continuous immersion dose-response bioassays analyzed using probit regression. A total of 72 unique studies that aligned with WHO protocols were assessed for publication bias using a funnel plot and Egger’s regression. Sensitivity and subgroup analyses were conducted to evaluate individual study contributions to the overall combined effect. Heterogeneity (I²) and combined effect values were estimated for 18 different species/active ingredient/IE concentration subgroup pairings. Heterogeneity (I²) ranged from 29.32 to 99.78% between the 18 subgroups, indicating inconsistency within the literature. The DL combined effect IE₅₀ varied from 0.048 ppb for Cx. pipiens exposed to pyriproxyfen to 1.818 ppb for Ae. albopictus exposed to methoprene. A certainty analysis indicated that 1 combined effect value exhibited high certainty, 8 out of 18 pairings were moderately certain, 6 exhibited low certainty and 3 exhibited very low certainty. The main causes of uncertainty (ranked) were inconsistency between studies, imprecision of the combined effect size, and possible publication bias. Our findings indicate that (1) robust DL combined effect IE₅₀ values could be established for all species/IGR pairings, providing essential benchmarks for future resistance assessments; (2) substantial heterogeneity among susceptible laboratory colonies complicates resistance detection in field-collected mosquitoes; and (3) a significant portion of the literature relies on reference mosquito strains that are likely not fully susceptible, further complicating resistance detection. This study was not registered and was supported by the North Shore Mosquito Abatement District. Full article

Insects, as the most diverse and numerous group in the animal kingdom, are at least partly dependent on the reproduction process, which is strictly regulated by the ‘classic’ insect hormones: juvenile hormone (JH), and 20-hydroxyecdysone (20E). However, the regulatory mechanism governing the reproduction of JH and 20E in Spodoptera frugiperda remains unclear. In this study, ovarian development and ovulation in female S. frugiperda were assessed through dissection of the ovaries following treatment with JH analog (JHA) and 20E. Moreover, the expression patterns of the JH-signal and 20E-signal-related genes were determined by quantitative PCR (qPCR), and RNA interference (RNAi) was used to investigate the role of JH and 20E-induced genes. Ovarian development was observed by microdissection, and JH and 20E titers were determined by ELISA. Kr-h1, Vg, and USP expression were determined by qPCR. Dissection and qPCR results showed that JHA and 20E promoted ovarian development, egg maturation, and egg laying by upregulating Methoprene-Tolerant (Met) and Ecdysone Receptor (EcR)expression. Additionally, the RNAi results showed that the injection of dsMet and dsEcR markedly delayed ovarian development, inhibited egg maturation, and halted egg production. Knockdown of Met and EcR significantly reduced JH and 20E content and inhibited the transcription of Kr-h1 and USP. These results indicate that JH and 20E facilitate adult reproduction through the methoprene-tolerant gene and ecdysone receptor gene in female S. frugiperda. Full article

This study focuses on the regulatory effects of genes encoding the juvenile hormone (JH) receptor methoprene-tolerant (Met) and transcription factor krüppel homolog 1 (Kr-h1) on the reproductive capacity of Coccinella septempunctata male adults. Met and Kr-h1 expression levels were analyzed in males fed on artificial diets with and without JH by quantitative real-time PCR, and the effects of Met and Kr-h1 on male reproduction were analyzed by RNA interference technology. Met transcription levels in 5- and 10-day-old males fed with a JH-supplemented diet were lower than those without JH. Kr-h1 expression in 5-day-old adult males was lower in diets lacking JH but was higher in 10-day-old males fed on a diet lacking JH. There were no significant differences in the testes sizes of male ladybugs injected with Met-dsRNA when compared to GFP-dsRNA; however, the testis volume of ladybugs injected with Kr-h1-dsRNA was smaller than those injected with GFP-dsRNA. After males were injected with Met-dsRNA and Kr-h1-dsRNA, the mean egg production by females decreased by 12.75% and 23.10%, respectively, at 20 d postinjection. Our results show that Met and Kr-h1 have important roles in regulating reproduction by directly affecting testes development in males and egg production in females. Full article

The conserved role of juvenile hormone (JH) signals in preventing larvae from precocious metamorphosis has been confirmed in insects. Crustaceans have different metamorphosis types from insects; we previously proved that methyl farnesoate (MF) can prohibit larvae metamorphosis in mud crabs, but the molecular signal of this process still needs to be elucidated. In this study, methoprene-tolerant (Met) of Scylla paramamosain was obtained and characterized, which we named Sp-Met. Sp-Met contains a 3360 bp ORF that encodes 1119 amino acids; the predicted protein sequences of Sp-Met include one bHLH, two PAS domains, one PAC domain, and several long unusual Gln repeats at the C-terminal. AlphaFold2 was used to predict the 3D structure of Sp-Met and the JH binding domain of Met. Furthermore, the binding properties between Sp-Met and MF were analyzed using CD-DOCK2, revealing a putative high affinity between the receptor and ligand. In silico site-directed mutagenesis suggested that insect Mets may have evolved to exhibit a higher affinity for both MF or JH III compared to the Mets of crustaceans. In addition, we found that the expression of Sp-Met was significantly higher in female reproductive tissues than in males but lower in most of the other examined tissues. During larval development, the expression variation in Sp-Met and Sp-Kr-h1 was consistent with the immersion effect of MF. The most interesting finding is that knockdown of Sp-Met blocked the inhibitory effect of MF on metamorphosis in the fifth zoea stage and induced pre-metamorphosis phenotypes in the fourth zoea stage. The knockdown of Sp-Met significantly reduced the expression of Sp-Kr-h1 and two ecdysone signaling genes, Sp-EcR and Sp-E93. However, only the reduction in Sp-Kr-h1 could be rescued by MF treatment. In summary, this study provides the first evidence that MF inhibits crustacean larval metamorphosis through Met and that the MF-Met→Kr-h1 signal pathway is conserved in mud crabs. Additionally, the crosstalk between MF and ecdysteroid signaling may have evolved differently in mud crabs compared to insects. Full article

Spodoptera frugiperda control methods have proved to be inefficient, which justifies the search for new control measures. In this search for botanical insecticides for controlling S. frugiperda, the following were evaluated: (i) the toxicity of essential oils (EOs) from Cinnamodendron dinisii, Eugenia uniflora, and Melaleuca armillaris; (ii) the effect of EOs on life table parameters against S. frugiperda; (iii) the chemical characterization of EOs; and (iv) the in silico interaction of the chemical constituents present in the three EOs with the molecular targets of S. frugiperda. The EO from E. uniflora had the lowest LD₅₀ (1.19 µg of EO/caterpillar). The major compounds bicyclogermacrene (18.64%) in C. dinisii and terpinolene (57.75%) in M. armillaris are highly predicted to interact with the octopamine receptor (OctpR). The compound 1,8-cineole (21.81%) in M. armillaris interacts mainly with a tolerant methoprene receptor (MET) and curzerene (41.22%) in E. uniflora, which acts on the OctpR receptor. Minor compounds, such as nerolidol in C. dinisii and β-elemene in E. uniflora, are highly ranked for multiple targets: AChE, MET, OctpR, and 5-HT1. It was concluded that the EO from E. uniflora negatively affects several biological parameters of S. frugiperda development and is promising as an active ingredient in formulations for controlling this insect pest. Full article

Eusocial insects have evolved specific defensive strategies to protect their colonies. In termite colonies, soldiers perform a colony-level defense by displaying mechanical biting, head-banging and mandible opening–closing behaviors. However, few studies have been reported on the factors modulating defensive behaviors in termites. Owing to JH (juvenile hormone) being involved in soldier differentiation, JH was speculated to affect defensive behaviors in termite soldiers. To determine the effect of JH on the defensive behaviors of termite soldiers, we performed a JHA-feeding and RaSsp1-silencing experiment and then tested the changes in defense-related behaviors, alarm pheromones and key JH signaling genes. The observed result was that after feeding workers with JHA, soldiers displayed the following: (1) decreased biting events and increased head-banging events; (2) a reduced expression of RaSsp1 and increased expression of Met (methoprene-tolerant, the nuclear receptor of JH) and Kr-h1 (the JH-inducible transcription factor Krüppel homolog 1); and (3) a decreased concentration of alarm pheromones, including α-pinene, β-pinene and limonene (+, −). Further study showed that soldiers silenced for RaSsp1 also exhibited (1) decreased biting events and increased head-banging events and (2) increased expression of Met and Kr-h1. In addition, soldiers stimulated by the alarm pheromone limonene displayed an increase in the frequency of mandible opening–closing and biting behavior. All of these results show that JHA influenced the defensive behaviors of termite soldiers, possibly via downregulating RaSsp1 expression, up-regulating Met and Kr-h1 and stimulating the secretion of alarm pheromones, suggesting that the JH pathway plays important roles in modulating social behaviors in termite colonies. Full article

Trogoderma granarium Everts, the khapra beetle, is a serious pest of stored products throughout the world. Larvae pose a significant threat to stored products because they feed on >100 different commodities, possess the ability to enter facultative diapause, and are difficult to detect. Control methods for T. granarium include fumigation, contact insecticides, trapping, and insecticide-incorporated packaging. The objective of this study was to determine the residual efficacy of two insecticide formulations (methoprene + deltamethrin + piperonyl butoxide synergist Gravista^® and methoprene + deltamethrin, DiaconIGR^®Plus). These insecticides were evaluated on three stored product commodities, corn, wheat, and brown rice, by exposing T. granarium larvae during a 12-month testing period. Both formulations significantly reduced adult emergence on corn and wheat for 12 months and on brown rice for up to 6 months. Adult emergence was highest at month 12 for corn (8.41%), and brown rice (85.88%), and month 9 for wheat (39.52%), treated with DiaconIGR^®Plus or Gravista^®, respectively. A biological index used to measure the development of exposed larvae on the treated grain from the larval stage (low values) to adult emergence (high values) was lower (fewer adults) on corn and wheat compared to controls. Despite differences in formulations, each of these grain protectants could be utilized by stored commodity managers to protect commodities during storage and transportation for T. granarium when and if this pest is detected at USA ports of entry. Full article

Juvenile hormones (JHs) play a central role in insect development, reproduction, and various physiological functions. Curcuminoids generally exhibit a wide range of biological activities, such as antioxidant, anti-inflammatory, antibacterial, and insecticidal, and they exhibit insect growth inhibitory effects. However, research on insecticidal properties of curcuminoids has been limited. Moreover, to the best of our knowledge, studies on JHs of insects and curcuminoids are lacking. Therefore, this study aimed to identify the substances that act as JH disruptors (JHDs) from edible plants. Demethoxycurcumin (DMC) and bisdemethoxycurcumin (BDMC), two curcuminoids from the turmeric plant Curcuma longa L. inhibited the formation of a methoprene-tolerant (Met)–Taiman (Tai) heterodimer complex in Drosophila melanogaster, as shown through in vitro yeast two-hybrid assays. An artificial diet containing 1% (w/v) DMC or BDMC significantly reduced the number of D. melanogaster larvae in a concentration-dependent manner; larval development was disrupted, preventing the progression of larvae to pupal stages, resulting in an absence of adults. Building on the results obtained in this study on curcuminoids, researchers can use our study as a reference to develop eco-friendly pesticides. Full article