Locomotion Inhibition of Cimex lectularius L. Following Topical, Sublethal Dose Application of the Chitin Synthesis Inhibitor Lufenuron

Sublethal Effects of α-Cypermethrin on the Behavioral Asymmetries and Mating Success of Alphitobius diaperinus

Sublethal exposure to insecticides can adversely impact various biological and behavioral characteristics of insects. Although α-cypermethrin has been previously tested for its effects on control of Alphitobius diaperinus, there is no knowledge about the effect of this insecticide on its behavioral asymmetries and mating success. Μales at all exposures (control, LC10, and LC30), that first approached their mate, showed right-biased tendency (approached their mate from their right side) in mate recognition. Females, however, showed variation in this behavior between the three exposures. Right-biased tendency of males in all treatment scenarios led to a higher percentage of successful copulations compared to the three other directions. For males that first approached their mate, the insecticide did not affect their lateralization of the first approach but did affect their copulation success. The duration of copulation time was reduced after the exposure to the insecticide, with the longest duration noted in the control females (63.0 s) and the lowest in the α-cypermethrin LC30 females (46.9 s). Moreover, at the α-cypermethrin LC10 exposure, mate recognition time was reduced, as opposed to α-cypermethrin LC30 exposure where mate recognition time was increased. These results can be further utilized to uncover the behavioral impacts of insecticides, enhancing the effectiveness of pest management in warehouses and poultry production facilities.

Sublethal Effects of Chlorantraniliprole on the Mobility Patterns of Sitophilus spp.: Implications for Pest Management

Chlorantraniliprole, an anthranilic diamide insecticide, has emerged as a promising solution for controlling agricultural pests because of its low mammalian toxicity and selectivity towards non-target organisms. This study investigated the sublethal effects of chlorantraniliprole on the mobility behavior of two significant stored-product pests, Sitophilus oryzae (L.) and Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae). Contact toxicity assays revealed varying susceptibility levels between the two species, with S. zeamais showing higher sensitivity. Subsequent analysis of mobility behavior, both in the presence and absence of food, indicated significant differences between chlorantraniliprole-exposed and control groups. While S. oryzae exhibited altered locomotion patterns and a decreased number of food approaches at sublethal concentrations, S. zeamais displayed increased walking time and reduced immobility periods. These findings highlight the importance of considering sublethal effects in understanding the overall impact of chlorantraniliprole on stored-product pests. Further research into the long-term consequences of sublethal exposure is warranted to inform more effective pest management strategies in storage.

Being exposed to low concentrations of pirimiphos-methyl and chlorfenapyr has detrimental effects on the mobility of Trogoderma granarium

BACKGROUND

Sublethal effects of insecticides may negatively affect several biological and behavioral traits of insects. The lethal effects of pirimiphos-methyl and chlorfenapyr have been previously showed on Trogoderma granarium, but little knowledge is available about their sublethal effects at low concentrations on both sexes. Herein, the sublethal effects of pirimiphos-methyl and chlorfenapyr on the mobility of T. granarium males and females were investigated.

RESULTS

Lethal concentration (LC) values of pirimiphos-methyl and chlorfenapyr were lower for T. granarium females than males. LC values on males were LC10  = 0.000788 and 0.00139 mg active ingredient (a.i.) cm-2 , LC30  = 0.00350 and 0.00535 mg a.i. cm-2 , and LC50  = 0.00986 and 0.0136 mg a.i. cm-2 for pirimiphos-methyl and chlorfenapyr respectively. LC on females were LC10  = 0.000704 and 0.00110 mg a.i. cm-2 , LC30  = 0.00323 and 0.00428 mg a.i. cm-2 , and LC50  = 0.00925 and 0.0110 mg a.i. cm-2 for pirimiphos-methyl and chlorfenapyr respectively. The walking duration of beetles exposed to LC30 of pirimiphos-methyl was significantly lower than the individuals exposed to LC10 and LC30 of both insecticides and control ones. Pirimiphos-methyl LC30 -exposed males remained more time on their back (101.7 s) than females (46.9 s), while the latter stayed immobile longer than males (381.7 s versus 371.9 s). The highest speed was recorded for control beetles (14.17 mm s-1 females vs. 12.44 mm s-1 males), while the lowest speed was observed in pirimiphos-methyl LC30 -treated males (8.36 mm s-1 ) and females (9.66 mm s-1 ).

CONCLUSIONS

Overall, males and females exposed to low concentrations of pirimiphos-methyl and chlorfenapyr showed reduced motility. This knowledge can be exploited further to unlock behavioral effects of insecticides for effective pest management programs in warehouses. © 2023 Society of Chemical Industry.

Sublethal and transgenerational effects of lufenuron on biological characteristics and expression of reproductive related genes in the fall armyworm, Spodoptera frugiperda

The fall armyworm, Spodoptera frugiperda, is a notorious polyphagous pest that causes serious economic losses in crucial crops and has invaded Africa and Asia. Lufenuron is widely used for controlling S. frugiperda in China, owing to its high toxicity against this key pest, and less pollution and little impact on natural enemies. In the present study, the sublethal and transgenerational effects of lufenuron on S. frugiperda were investigated to provide in-depth information for the rational use of lufenuron. Results showed that the development time and pupae weight were not significantly affected following exposure of females to LC10 and LC25 and male S. frugiperda to the LC10 of lufenuron. However, LC25 exposure significantly reduced pupal and total development time and pupae weight of male S. frugiperda. The longevity of S. frugiperda adults was prolonged by lufenuron and the fecundity of S. frugiperda treated with LC10 of lufenuron was significantly increased by 40% compared to the control. In addition, our study demonstrated that the LC25 of lufenuron had transgenerational effects on the progeny generation. The development time of female S. frugiperda whose parents were exposed to LC25 of lufenuron was significantly decreased compared to the control. And then, the expression profiles of Vg, VgR, JHEH, JHE, JHAMT, JHBP, CYP307A1, CYP306A1, CYP302A1 and CYP314A1 genes involved in insect reproduction and development were analyzed using Quantitative Real-Time PCR (RT-qPCR). Results showed that Vg, VgR, JHE, JHAMT, and CYP306A1 were significantly upregulated at the LC10 of lufenuron, which revealed that these upregulated genes might be linked with increased fecundity of S. frugiperda. Taken together, these findings highlighted the importance of sublethal and transgenerational effects under laboratory conditions and these effects may change the population dynamics in the field. Therefore, our study provided valuable information for promoting the rational use of lufenuron for controlling S. frugiperda.

Sub-Lethal Effects of Pirimiphos-Methyl Are Expressed to Different Levels in Wings of Three Stored-Product Coleopterans: A Geometric Morphometrics Investigation

Tenebrio molitor L. (Coleoptera: Tenebrionidae), Prostephanus truncatus (Horn), and Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae) are noxious insect pests of grains in storages. Pirimiphos-methyl is widely used to protect grains at the post-harvest stage. However, the sub-lethal impact of this active ingredient on the offspring of all three coleopterans remains unknown. Thus, mated females of each species were exposed separately to pirimiphos-methyl at short exposures (30 min, 3, 5, 8, 16, 24, and 36 h), where the elytra and hindwings of the adult progeny were analyzed with the geometric morphometrics method. Males and females of all species were incorporated into the analysis. The results revealed variability among species. Tenebrio molitor was the most sensitive among three species, displaying significant deformations in the elytra and hindwings. Males had more conspicuous morphological changes than females. Prostephanus truncatus hindwings exhibited deformities after 36 h of exposure to pirimiphos-methyl. In contrast, R. dominica offspring were not affected by pirimiphos-methyl. In light of our findings, organophosphorus insecticides may cause variable sub-lethal effects to stored-product insects. This issue may lead to different insecticidal treatments according to the targeted stored-product species.

The Developmental Transcriptome of Bagworm, Metisa plana (Lepidoptera: Psychidae) and Insights into Chitin Biosynthesis Genes

Bagworm, Metisa plana (Lepidoptera: Psychidae) is a ubiquitous insect pest in the oil palm plantations. M. plana infestation could reduce the oil palm productivity by 40% if it remains untreated over two consecutive years. Despite the urgency to tackle this issue, the genome and transcriptome of M. plana have not yet been fully elucidated. Here, we report a comprehensive transcriptome dataset from four different developmental stages of M. plana, comprising of egg, third instar larva, pupa and female adult. The de novo transcriptome assembly of the raw data had produced a total of 193,686 transcripts, which were then annotated against UniProt, NCBI non-redundant (NR) database, Gene Ontology, Cluster of Orthologous Group, and Kyoto Encyclopedia of Genes and Genomes databases. From this, 46,534 transcripts were annotated and mapped to 146 known metabolic or signalling KEGG pathways. The paper further identified 41 differentially expressed transcripts encoding seven genes in the chitin biosynthesis pathways, and their expressions across each developmental stage were further analysed. The genetic diversity of M. plana was profiled whereby there were 21,516 microsatellite sequences and 379,895 SNPs loci found in the transcriptome of M. plana. These datasets add valuable transcriptomic resources for further study of developmental gene expression, transcriptional regulations and functional gene activities involved in the development of M. plana. Identification of regulatory genes in the chitin biosynthesis pathway may also help in developing an RNAi-mediated pest control management by targeting certain pathways, and functional studies of the genes in M. plana.

Benzoylphenyl ureas as veterinary antiparasitics. An overview and outlook with emphasis on efficacy, usage and resistance

Six benzoylphenyl ureas are currently used in formulations approved as veterinary medicines: diflubenzuron for fly control mainly on cattle, lice and blowfly strike control on sheep, and lice control on farmed salmonids; lufenuron for flea control on dogs and cats and for lice control on farmed salmonids; triflumuron for lice and blowfly strike control on sheep; fluazuron for tick control on cattle; teflubenzuron for lice control on farmed salmon; and novaluron for fly and tick control on cattle and for flea control on dogs. Resistance to diflubenzuron and triflumuron has already been reported for sheep body lice and blowflies, and to fluazuron in cattle ticks. These and other minor veterinary usages, as well as the current status of resistance, are reviewed and perspectives for future opportunities are discussed based on unexplored potentials and threats posed by future resistance development.