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The rice leaf folder, Cnaphalocrocis medinalis (Lepidoptera: Pyralidae), is a major migratory pest in rice agriculture. This pest is characterised by its larvae's ability to fold rice leaves using silk, a behaviour that culminates in the formation of a silken cocoon during the pupal stage. The fibroin light chain (CmFib‐L) gene is crucial for silk production, yet its specific function in C. medinalis has reminded elusive. This study presents a comprehensive analysis of the CmFib‐L gene, revealing its complete open reading frame (ORF) and expression patterns. Notably, the gene is highly expressed in the fifth‐instar larvae and the silk gland, which are critical stages for silk production. Our experiments demonstrate that silencing the CmFib‐L gene leads to a reduction in pupal weight, an extension of the pupal stage and a disorganised silk cocoon. Furthermore, the larval behaviour of leaf folding and spinning is significantly impaired when the expression of CmFib‐L is downregulated. These findings not only show the importance of fibroin light chain in silk production but also reveal a new target gene to regulate and control the behaviour and development of C. medinalis. [ABSTRACT FROM AUTHOR]

Simple Summary: The rice leaf-roller Cnaphalocrocis medinalis is a migratory pest of rice. Monitoring its population is important in integrated pest management systems. Trapping them with a sex pheromone or plant odor has been used in population monitoring. We studied the physiological status of adults trapped by sex pheromones and floral odors. In the immigrant group, the number of males caught in the floral trap was greater than those caught by the sex pheromone trap. The volumes of testes in adults caught using the above two trapping methods were similar. In the local breeding group, the number of males caught by sex pheromone trapping was greater than that by floral trapping. The volume of testes was smaller in males caught in the floral odor trap compared to the pheromone trap. In the emigrant group, the adult olfactory response to the sex pheromone and floral odor was low. The number of eggs laid by the females in the local breeding group was greater in those caught in the sweep net in comparison with those caught in the floral odor trap. The rice leaf-roller Cnaphalocrocis medinalis is an important migratory pest of rice. We conducted a study to determine the physiological status of adults trapped by a sex pheromone and floral odor. In the immigrant group, the number of males trapped by the floral odor was greater than the number caught by sex pheromone trapping. The volume of testes was similar in the above two trapping methods but was smaller than in the sweep net method. The ovary developmental grade, mating rate, and number of matings of females caught in floral odor trap were higher than in those caught in the sweep net. In the local breeding group, the number of males trapped by sex pheromones was greater than the number trapped by the floral odor. The volume of testes was smaller in the floral odor trap compared to the pheromone trap group, with the largest in the sweep net group. The ovarian developmental grade, mating rate, and number of matings of females were significantly higher in the floral odor trap group than in the sweep net group. In the emigrant group, the adult olfactory response to the sex pheromone and floral odor was low. The volume of testes was larger in the sweep net group compared to the moths caught by floral odor trapping. The number of eggs laid by female immigrants trapped by the floral odor and sweep net was similar, while the number in the local breeding group was greater in moths caught with the sweep net in comparison with those caught by the floral odor trap. The difference in egg hatchability between the two trapping methods in both immigrants and local breedings was not significant. [ABSTRACT FROM AUTHOR]

In the face of rising global temperatures, the mechanisms behind an organism's ability to acclimate to heat stress remain enigmatic. The rice leaf folder, Cnaphalocrocis medinalis, traditionally viewed as temperature‐sensitive, paradoxically exhibits robust larval acclimation to heat stress. This study used the heat‐acclimated strain HA39, developed through multigenerational exposure to 39°C during the larval stage, and the unacclimated strain HA27 reared at 27°C to unravel the transgenerational effects of heat acclimation and its regulatory mechanisms. Heat acclimation for larvae incurred a fitness cost in pupae when exposed to high temperature, yet a significant transgenerational effect surfaced, revealing heightened fitness benefit in pupae from HA39, even without additional heat exposure during larval recovery at 27°C. This transgenerational effect exhibited a short‐term memory, diminishing after two recovery generations. Moreover, the effect correlated with increased superoxide dismutase (SOD) enzyme activity and expression levels of oxidoreductase genes, representing physiological and molecular foundations of heat acclimation. Heat‐acclimated larvae displayed elevated DNA methylation levels, while pupae from HA39, in recovery generations, exhibited decreased methylation indicated by the upregulation of a demethylase gene and downregulation of two methyltransferase genes at high temperatures. In summary, heat acclimation induces DNA methylation, orchestrating heat‐stress memory and influencing the expression levels of oxidoreductase genes and SOD activity. Heat‐stress memory enhances the acclimation of the migratory insect pest to global warming. [ABSTRACT FROM AUTHOR]

Abstract The relationship between climate conditions and pest life is a key determinant of their distribution. Cnaphalocrocis medinalis Guenee, a major rice pest, exhibits outbreaks and its distribution patterns closely linked to meteorological factors. By using 244 actual distribution and occurrence data of C. medinalis along with 8 bioclimatic data, and employing the MaxEnt model and ArcGIS, combined with the latest SSPs climate scenario data, this study evaluated the risk region distribution status in the current period and predicted changes in China from 2040 to 2100. The results indicate that an overall increase in the risk area for C. medinalis, particularly under SSP245 scenario during 2040–2060. While Low-risk areas are expected to decrease, Medium and High-risk areas are projected to increase significantly, with worsening pest infestations anticipated in southern Hubei, eastern Hunan, most of Jiangxi, central Fujian, northern Guangdong, and southern Jiangsu. Regions such as central Liaoning are expected to reach the minimum survival standard for C. medinalis in future, leading to the northward shift in risk areas. Difference plots highlighted areas of increased and decreased suitability, providing actionable insights for policymakers. Regions with increased suitability align with the predicted northward shift of many agricultural pests, necessitating enhanced monitoring, specific pest control measures, and updated agricultural policies to address changing risk profiles. Additionally, the centroid analysis showed a northwest shift direction in future, primarily located at the junction of Shaoyang City and Loudi City, situated around 27–28 °N degrees north latitude and 111–113 °E. The study underscores the significant impact of climate change on the distribution of rice leaf roller, providing valuable insights for agricultural planning and management. The northward and westward expansion of risk areas necessitates adaptive strategies to mitigate potential impacts on agriculture. Enhanced monitoring, integrated pest management, and the development of pest-resistant crops are essential for addressing future challenges posed by climate change.

Rice leaffolder, Cnaphalocrocis medinalis (Lepidoptera: Plutellidae) is an important migratory pest in Asia. While many lepidopteran species are known to enhance adult life history by obtaining supplementary nutrition, little is known about the effects of adult diet on C. medinalis. We first examined the effects of offering five dilutions of honey solution (0%, 5%, 10%, 15% and 20%) on the longevity, fecundity and ovary development of adult C. medinalis. We then compared the effects of 10% honey solution to 25% glucose solution, which was previously reported to be the best adult diet for C. medinalis. We found that adult male and female C. medinalis fed 5%–20% honey solution lived significantly longer than those fed just water. Importantly, a honey–based diet accelerated and increased ovary development and prolonged the oviposition period, leading to higher fecundity. More specifically, females fed 5%–15% honey solution had the highest fecundity, followed by 20% honey solution, and the lowest when fed only water. In addition, the oviposition rate was 100% in females fed 10% and 15% honey solution. When we compared 10% honey solution to 25% glucose solution, those fed honey solution had significantly higher estimated female performance, which is a composite measure consisting of fecundity, percentage of egg‐laying females and percentage of eggs that hatched. Overall, our findings indicate that adult diet quality significantly impacts C. medinalis performance and that using a 10%–15% honey solution is optimal for mass‐rearing under laboratory conditions. [ABSTRACT FROM AUTHOR]

Abstract Background Numerous insect species undertake long-distance migrations on an enormous scale, with great implications for ecosystems. Given that take-off is the point where it all starts, whether and how the external light and internal circadian rhythm are involved in regulating the take-off behaviour remains largely unknown. Herein, we explore this issue in a migratory pest, Cnaphalocrocis medinalis, via behavioural observations and RNAi experiments. Results The results showed that C. medinalis moths took off under conditions where the light intensity gradually weakened to 0.1 lx during the afternoon or evening, and the take-off proportions under full spectrum or blue light were significantly higher than that under red and green light. The ultraviolet-A/blue light–sensitive type 1 cryptochrome gene (Cmedcry1) was significantly higher in take-off moths than that of non-take-off moths. In contrast, the expression of the light-insensitive CRY2 (Cmedcry2) and circadian genes (Cmedtim and Cmedper) showed no significant differences. After silencing Cmedcry1, the take-off proportion significantly decreased. Thus, Cmedcry1 is involved in the decrease in light intensity induced take-off behaviour in C. medinalis. Conclusions This study can help further explain the molecular mechanisms behind insect migration, especially light perception and signal transmission during take-off phases.

Background: Numerous insect species undertake long-distance migrations on an enormous scale, with great implications for ecosystems. Given that take-off is the point where it all starts, whether and how the external light and internal circadian rhythm are involved in regulating the take-off behaviour remains largely unknown. Herein, we explore this issue in a migratory pest, Cnaphalocrocis medinalis, via behavioural observations and RNAi experiments. Results: The results showed that C. medinalis moths took off under conditions where the light intensity gradually weakened to 0.1 lx during the afternoon or evening, and the take-off proportions under full spectrum or blue light were significantly higher than that under red and green light. The ultraviolet-A/blue light–sensitive type 1 cryptochrome gene (Cmedcry1) was significantly higher in take-off moths than that of non-take-off moths. In contrast, the expression of the light-insensitive CRY2 (Cmedcry2) and circadian genes (Cmedtim and Cmedper) showed no significant differences. After silencing Cmedcry1, the take-off proportion significantly decreased. Thus, Cmedcry1 is involved in the decrease in light intensity induced take-off behaviour in C. medinalis. Conclusions: This study can help further explain the molecular mechanisms behind insect migration, especially light perception and signal transmission during take-off phases. [ABSTRACT FROM AUTHOR]

A field survey was carried out in the farmer's field located at Chutsolie colony, Chumukedima, Nagaland, from July to November 2022 using light traps to study the incidence of lepidopteran pests occurring in rice, Oryza sativa L. The survey was conducted from the vegetative till harvesting stages of paddy. Fortnightly, observations of the lepidopteran pests were done and correlated with the weather parameters. During the survey, four lepidopteran pests, namely, Cnaphalocrocis medinalis (Guenee), Leucania loreyi (Duponchel), Melanitis leda (Linnaeus), and Scirpophaga incertulas (Walker) were observed. The highest peak population of C. medinalis (Guenee), M. leda (Linnaeus), and S. incertulas (Walker) were observed on the 37th standard mean week (SMW) (i.e., vegetative stage) whereas the highest population of L. loreyi on 41st SMW. (i.e., reproductive stage). The species M. leda constituted the highest population (75) and persisted in the field till the harvest, followed by S. incertulas (51), and C. medinalis (47). The species L. loreyi was the least in numbers (16). Among the species recorded, L. loreyi was the new record from Nagaland. [ABSTRACT FROM AUTHOR]

Pesticide treatment of rice seeds has been used for decades to control pests. The efficacy of chlorantraniliprole seed treatment to control pests is now well established and can last for > 90 days, even though the residue content of chlorantraniliprole in rice plants is sharply reduced by this time. We found that 60 days after chlorantraniliprole seed treatment, the dose of chlorantraniliprole in rice plants was much lower than the LC50 of chlorantraniliprole for the arthropod pests Cnaphalocrocis medinalis, Chilo suppressalis and Sesamia inferens; however, the treatment still provided control, raising the issue of how chlorantraniliprole seed treatment exerts long-term control. Untargeted metabolomics analyses showed that jasmonic acid (JA) and its metabolic derivatives were induced after seed treatment. In rice shoots and roots, the expression levels of three key genes in the JA biosynthesis pathway, AOS2, AOC and OPR7, were up-regulated. After mechanical damage, there were significant differences in gene expression patterns between the seed treated plants and the controls. Using a bioassay with two JA-deficient lines (AOC and MYC2 knockouts) and a wildtype line (XS11), we showed that the mortality rate of C. suppressalis fed on XS11 plants from treated seeds was higher than the mortality rate on JA-deficient plants from treated seeds. Thus, JA seems to play an important role in pest mortality after chlorantraniliprole seed treatment, providing a possible basis for long-term pest control from the seed treatment. These results point to better ways of using seed treatment to reduce pesticide applications. [ABSTRACT FROM AUTHOR]

The composition of microbiota in the digestive tract gut is essential for insect physiology, homeostasis, and pathogen infection. Little is known about the interactions between microbiota load and oral infection with baculoviruses. CnmeGV is an obligative baculovirus to Cnaphalocrocis medinalis. We investigated the impact of CnmeGV infection on the structure of intestinal microbes of C. medinalis during the initial infection stage. The results revealed that the gut microbiota profiles were dynamically driven by pathogen infection of CnmeGV. The numbers of all the OTU counts were relatively higher at the early and later stages, while the microbial diversity significantly increased early but dropped sharply following the infection. The compositional abundance of domain bacteria Firmicutes developed substantially higher. The significantly enriched and depleted species can be divided into four groups at the species level. Fifteen of these species were ultimately predicted as the biomarkers of CnmeGV infection. CnmeGV infection induces significant enrichment of alterations in functional genes related to metabolism and the immune system, encompassing processes such as carbohydrate, amino acid, cofactor, and vitamin metabolism. Finally, the study may provide an in-depth analysis of the relationship between host microbiota, baculovirus infection, and pest control of C. medinalis. [ABSTRACT FROM AUTHOR]

Abstract Rice leaf folder, Cnaphalocrocis medinalis (Guenée), is one of the most serious pests on rice. At present, chemical control is the main method for controlling this pest. However, the indiscriminate use of chemical insecticides has non-target effects and may cause environmental pollution. Besides, leaf curling behavior by C. medinalis may indirectly reduce the efficacy of chemical spray. Therefore, it is crucial to cultivate efficient rice varieties resistant to this pest. Previous studies have found that three different rice varieties, Zhongzao39 (ZZ39), Xiushui134 (XS134), and Yongyou1540 (YY1540), had varying degrees of infestation by C. medinalis. However, it is currently unclear whether the reason for this difference is related to the difference in defense ability of the three rice varieties against the infestation of C. medinalis. To explore this issue, the current study investigated the effects of three rice varieties on the growth performance and food utilization capability of the 4th instar C. medinalis. Further, it elucidated the differences in defense responses among different rice varieties based on the differences in leaf physiological and biochemical indicators and their impact on population occurrence. The results showed that the larval survival rate was the lowest, and the development period was significantly prolonged after feeding on YY1540. This was not related to the differences in leaf wax, pigments, and nutritional components among the three rice varieties nor to the feeding preferences of the larvae. The rate of superoxide anion production, hydrogen peroxide content, and the activity of three protective enzymes were negatively correlated with larval survival rate, and they all showed the highest in YY1540 leaves. Compared to other tested varieties, although the larvae feeding on YY1540 had higher conversion efficiency of ingested food and lower relative consumption rate, their relative growth was faster, indicating stronger food utilization capability. However, they had a lower accumulation of protein. This suggests that different rice varieties had different levels of oxidative stress after infestation by C. medinalis. The defense response of YY1540 was more intense, which was not conducive to the development of the larvae population. These results will provide new insights into the interaction mechanism between different rice varieties and C. medinalis and provide a theoretical basis for cultivating rice varieties resistant to this pest.

Odorant-binding proteins (OBPs) play important roles in the insect olfactory system since they bind external odor molecules to trigger insect olfactory responses. Previous studies have identified some plant-derived volatiles that attract the pervasive insect pest Cnaphalocrocis medinalis (Lepidoptera: Pyralidae), such as phenylacetaldehyde, benzyl acetate, 1-heptanol, and hexanal. To characterize the roles of CmedOBPs in the recognition of these four volatiles, we analyzed the binding abilities of selected CmedOBPs to each of the four compounds, as well as the expression patterns of CmedOBPs in different developmental stages of C. medinalis adult. Antennaes of C. medinalis adults were sensitive to the studied plant volatile combinations. Expression levels of multiple CmedOBPs were significantly increased in the antennae of 2-day-old adults after exposure to volatiles. CmedOBP1, CmedOBP6, CmedPBP1, CmedPBP2, and CmedGOBP2 were significantly up-regulated in the antennae of volatile-stimulated female and male adults when compared to untreated controls. Fluorescence competition assays confirmed that CmedOBP1 could strongly bind 1-heptanol, hexanal, and phenylacetaldehyde; CmedOBP15 strongly bound benzyl acetate and phenylacetaldehyde; and CmedOBP26 could weakly bind 1-heptanol. This study lays a theoretical foundation for further analysis of the mechanisms by which plant volatiles can attract C. medinalis. It also provides a technical basis for the future development of efficient plant volatile attractants of C. medinalis. [ABSTRACT FROM AUTHOR]

Cnaphalocrocis medinalis is an important migratory pest in rice production. In order to develop a compound pesticide suitable for seed treatment and effective long-term control of C. medinalis, the optimal ratio of chlorantraniliprole and monosultap, as well as the field control effect, was studied through indoor systematic action test, field effect verification, and pesticide residue detection in rice plant. The long-term prevention and control mechanism of the compound agent had been preliminarily clarified. The results from the systematic action test indicated that the highest co-toxicity coefficient and strongest systemic absorption occurred when the mass concentration ratio of chlorantraniliprole and monosultap was 2﹕3. The chlorantraniliprole + monosultap 25% seed treatment suspension concentrate (FS), including 10% chlorothalonil and 15% benzamide, was prepared at doses ranging from 7.5-15 g/kg (seeds). This formulation is safe for seed germination and seedling emergence. The field experiment showed that the application of chlorantraniliprole + monosultap 25% FS at 7.5-15 g/kg (seeds) significantly controlled C. medinalis in the rice field, maintaining effective leaf preservation for an extended period. Even after 94 days post-seeding, approximately 70% leaf protection effect was observed. The detection of pesticide content in rice plant showed that the sustained control capability of chlorantraniliprole + monosultap 25% FS against C. medinalis was primarily associated with the chlorantraniliprole content in the leaves. Although monosultap in the compound formulation degraded relatively quickly, its presence enhanced the absorption rate of chlorantraniliprole by rice roots during the seedling stage. This study can provide a theoretical basis and technical reference for the development the seed treatment agents for the control C. medinalis. [ABSTRACT FROM AUTHOR]

Rice leaf folder, Cnaphalocrocis medinalis (Guenée), is one of the most serious pests on rice. At present, chemical control is the main method for controlling this pest. However, the indiscriminate use of chemical insecticides has non-target effects and may cause environmental pollution. Besides, leaf curling behavior by C. medinalis may indirectly reduce the efficacy of chemical spray. Therefore, it is crucial to cultivate efficient rice varieties resistant to this pest. Previous studies have found that three different rice varieties, Zhongzao39 (ZZ39), Xiushui134 (XS134), and Yongyou1540 (YY1540), had varying degrees of infestation by C. medinalis. However, it is currently unclear whether the reason for this difference is related to the difference in defense ability of the three rice varieties against the infestation of C. medinalis. To explore this issue, the current study investigated the effects of three rice varieties on the growth performance and food utilization capability of the 4th instar C. medinalis. Further, it elucidated the differences in defense responses among different rice varieties based on the differences in leaf physiological and biochemical indicators and their impact on population occurrence. The results showed that the larval survival rate was the lowest, and the development period was significantly prolonged after feeding on YY1540. This was not related to the differences in leaf wax, pigments, and nutritional components among the three rice varieties nor to the feeding preferences of the larvae. The rate of superoxide anion production, hydrogen peroxide content, and the activity of three protective enzymes were negatively correlated with larval survival rate, and they all showed the highest in YY1540 leaves. Compared to other tested varieties, although the larvae feeding on YY1540 had higher conversion efficiency of ingested food and lower relative consumption rate, their relative growth was faster, indicating stronger food utilization capability. However, they had a lower accumulation of protein. This suggests that different rice varieties had different levels of oxidative stress after infestation by C. medinalis. The defense response of YY1540 was more intense, which was not conducive to the development of the larvae population. These results will provide new insights into the interaction mechanism between different rice varieties and C. medinalis and provide a theoretical basis for cultivating rice varieties resistant to this pest. [ABSTRACT FROM AUTHOR]

In 2021, the fourth-generation Cnaphalocrocis medinalis in the Yangtze River region of Jiangsu Province reached a large occurrence level. Its main occurrence characteristics are long duration of adult peak, high amount of eggs in the field and serious damage. The occurrence causes of field management, climate, pest situation and control were analyzed comprehensively. Then, the control measures such as strengthening cultivation management, strengthening monitoring and early warning, controlling timely prevention and control, strictly selecting high-efficiency pesticides, strengthening green prevention and control, scientific and standardized medication, increasing publicity and deepening technical guidance were put forward. [ABSTRACT FROM AUTHOR]

Simple Summary: The rice leaf roller, Cnaphalocrocis medinalis, is a migratory insect pest threatening rice production. Monitoring its population dynamics is a critical component of the integrated management system for this pest. Plant odor-trapping has been used as a tool for population monitoring. However, there is a lack of knowledge on the molecular mechanism by which the C. medinalis moth recognizes the plant odor. In the present study, we amplified 12 odor receptor genes and tested differential expression of these genes in male and female moths of C. medinalis. We identified the function of three olfactory receptor genes in C. medinalis. CmedOR31 was a specific receptor for geraniol, and CmedOR32 was a broad-spectrum OR receptor that responds to both foliar odor and floral scent. The ligands of CmedOR1 were linalool, phenethyl alcohol, 2-phenylethanol, and phenylacetaldehyde. CmedOR1 belonged to a unique conserved OR lineage that strongly responded to phenylacetaldehyde in the evolution of Glossata species, and the OR1 expression in C. medinalis antennae was significantly higher in females than in males. CmedOR1 was the odor receptor for C. medinalis adults to locate food sources. Cnaphalocrocis medinalis (Lepidoptera: Crambidae) is a migratory insect pest on rice crops. The migratory C. medinalis population in a particular location may be immigrants, local populations, emigrants, or a mix of these. Immigrants are strongly attracted to plant odor. We conducted research to identify the olfactory receptors in a floral scent mixture that is strongly attractive to C. medinalis. Through gene cloning, 12 olfactory receptor (OR) genes were amplified and expressed in Xenopus oocytes in vitro, and three of them were found to be responsive to plant foliar and floral volatiles. These were CmedOR31, a specific receptor for geraniol; CmedOR32, a broad-spectrum OR gene that responded to both foliar and floral odors; and CmedOR1, which strongly responded to 10−4 M phenylacetaldehyde. The electrophysiological response to phenylacetaldehyde was extremely high, with a current of 3200 ± 86 nA and an extremely high sensitivity. We compared the phylogenetic tree and sequence similarity of CmedOR genes and found that CmedOR1 belonged to a uniquely conserved OR pedigree in the evolution of Glossata species, and the ORs of this pedigree strongly responded to phenylacetaldehyde. The expression of OR1 was significantly higher in the females than in the males. Localization of CmedOR1 in the antennae of C. medinalis by fluorescence in situ hybridization showed that CmedOR1 was expressed in both males and females. CmedOR1 may be an odor receptor used by females to locate food sources. The function of these ORs and their role in pest monitoring were discussed. [ABSTRACT FROM AUTHOR]

The rice leaf folder, Cnaphalocrocis medinalis (Lepidoptera: Pyralidae), is a notorious pest of rice in Asia. The larvae and adults of C. medinalis utilize specialized chemosensory systems to adapt to different environmental odors and physiological behaviors. However, the differences in chemosensory genes between the olfactory organs of these two different developmental stages remain unclear. Here, we conducted a transcriptome analysis of larvae heads, male antennae, and female antennae in C. medinalis and identified 131 putative chemosensory genes, including 32 OBPs (8 novel OBPs), 23 CSPs (2 novel CSPs), 55 ORs (17 novel ORs), 19 IRs (5 novel IRs) and 2 SNMPs. Comparisons between larvae and adults of C. medinalis by transcriptome and RT-qPCR analysis revealed that the number and expression of chemosensory genes in larval heads were less than that of adult antennae. Only 17 chemosensory genes (7 OBPs and 10 CSPs) were specifically or preferentially expressed in the larval heads, while a total of 101 chemosensory genes (21 OBPs, 9 CSPs, 51 ORs, 18 IRs, and 2 SNMPs) were specifically or preferentially expressed in adult antennae. Our study found differences in chemosensory gene expression between larvae and adults, suggesting their specialized functions at different developmental stages of C. medinalis. These results provide a theoretical basis for screening chemosensory genes as potential molecular targets and developing novel management strategies to control C. medinalis. [ABSTRACT FROM AUTHOR]

The rice leaf-roller Cnaphalocrocis medinalis is an important migratory pest of rice. We conducted a study to determine the physiological status of adults trapped by a sex pheromone and floral odor. In the immigrant group, the number of males trapped by the floral odor was greater than the number caught by sex pheromone trapping. The volume of testes was similar in the above two trapping methods but was smaller than in the sweep net method. The ovary developmental grade, mating rate, and number of matings of females caught in floral odor trap were higher than in those caught in the sweep net. In the local breeding group, the number of males trapped by sex pheromones was greater than the number trapped by the floral odor. The volume of testes was smaller in the floral odor trap compared to the pheromone trap group, with the largest in the sweep net group. The ovarian developmental grade, mating rate, and number of matings of females were significantly higher in the floral odor trap group than in the sweep net group. In the emigrant group, the adult olfactory response to the sex pheromone and floral odor was low. The volume of testes was larger in the sweep net group compared to the moths caught by floral odor trapping. The number of eggs laid by female immigrants trapped by the floral odor and sweep net was similar, while the number in the local breeding group was greater in moths caught with the sweep net in comparison with those caught by the floral odor trap. The difference in egg hatchability between the two trapping methods in both immigrants and local breedings was not significant.

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Background: As a member of the immunoglobulin superfamily, hemolins play a vital role in insect development and defense against pathogens. However, the innate immune response of hemolin to baculovirus infection varies among different insects. Methods and results: In this study, the hemolin-like gene from a Crambidae insect, Cnaphalocrocis medinalis, CmHem was cloned, and its role in insect development and baculovirus infection was analyzed. A 1,528 bp contig as potential hemolin-like gene of C. medinalis was reassembled from the transcriptome. Further, the complete hemolin sequence of C. medinalis (CmHem) was cloned and sequenced. The cDNA of CmHem was 1,515 bp in length and encoded 408 amino acids. The deduced amino acid of CmHem has relatively low identities (41.9-62.3%) to various insect hemolins. However, it contains four Ig domains similarity to other insect hemolins. The expression level of CmHem was the highest in eggs, followed by pupae and adults, and maintained a low expression level at larval stage. The synthesized siRNAs were injected into mature larvae, and the CmHem transcription decreased by 51.7%. Moreover, the abdominal somites of larvae became straightened, could not pupate normally, and then died. Infection with a baculovirus, C. medinalis granulovirus (CnmeGV), the expression levels of CmHem in the midgut and fat body of C. medinalis significantly increased at 12 and 24 h, respectively, and then soon returned to normal levels. Conclusions: Our results suggested that hemolin may be related to the metamorphosis of C. medinalis. Exposure to baculovirus induced the phased expression of hemolin gene in the midgut and fat body of C. medinalis, indicated that hemolin involved in the immune recognition of Crambidae insects to baculovirus. [ABSTRACT FROM AUTHOR]

Background: The rice leaffolder, Cnaphalocrocis medinalis (Guenée), has become an increasingly occurring pest in Asia in recent years. Chemical control remains the most efficient and primary tool for controlling this pest. In this study, we report the resistance status of C. medinalis in China to multiple insecticides including chlorantraniliprole and the main resistance mechanism. Results: Significant variations among field populations of C. medinalis in their resistance to 10 insecticides were observed during 2019–2022. Most of the tested field populations have developed low‐to‐moderate levels of resistance to abamectin (RR = 2.4–22.2), emamectin benzoate (RR = 1.9–40.3) and spinetoram (RR = 4.2–24.8). Some field populations have developed low resistance to chlorpyrifos (RR = 0.9–6.8). Indoxacarb, metaflumizone, methoxenozide and Bacillus thuringiensis (Bt) potency against all tested populations remained similar. For diamides, significantly higher levels of resistance to chlorantraniliprole (RR = 64.9–113.7) were observed in 2022, whereas all tested field populations in 2019–2021 exhibited susceptible or moderate resistance level to chlorantraniliprole (RR = 1.3–22.1). Cross‐resistance between chlorantraniliprole and tetraniliprole was significant. Analysis of ryanodine receptor (RyR) mutations showed that mutation of I4712M was present in resistant populations of C. medinalis with different levels of chlorantraniliprole resistance and was the main mechanism conferring diamide resistance. Mutation of Y4621D also was detected in one tested population. Resistance management strategies for the control of C. medinalis are discussed. Conclusion: C. medinalis has developed high level of resistance to chlorantraniliprole. RyR mutations were deemed as the mechanism. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

The composition of microbiota in the digestive tract gut is essential for insect physiology, homeostasis, and pathogen infection. Little is known about the interactions between microbiota load and oral infection with baculoviruses. CnmeGV is an obligative baculovirus to Cnaphalocrocis medinalis. We investigated the impact of CnmeGV infection on the structure of intestinal microbes of C. medinalis during the initial infection stage. The results revealed that the gut microbiota profiles were dynamically driven by pathogen infection of CnmeGV. The numbers of all the OTU counts were relatively higher at the early and later stages, while the microbial diversity significantly increased early but dropped sharply following the infection. The compositional abundance of domain bacteria Firmicutes developed substantially higher. The significantly enriched and depleted species can be divided into four groups at the species level. Fifteen of these species were ultimately predicted as the biomarkers of CnmeGV infection. CnmeGV infection induces significant enrichment of alterations in functional genes related to metabolism and the immune system, encompassing processes such as carbohydrate, amino acid, cofactor, and vitamin metabolism. Finally, the study may provide an in-depth analysis of the relationship between host microbiota, baculovirus infection, and pest control of C. medinalis.

The rice leaf folder, Cnaphalocrocis medinalis, is a significant migratory pest that restricts rice production in Asia and Africa, and monitoring and early warning measures are the basis for its management. Based on its regional migratory path in China, the pest population dynamics were monitored from 2020 to 2021 using food attractants. In this study, we also used internal reproductive system dissection to determine the adult age and reproductive developmental state. The monitoring results indicated that the trapping dynamics of C. medinalis males using food attractants and sex pheromones were approximately similar. Both trapping methods yielded C. medinalis males of different ages, with an identical age structure for both trap types. Dissection analysis of the reproductive system of females trapped using the food attractants indicated that in 2020, the population of C. medinalis in Liling, Hunan Province, was indigenous, while populations in other monitoring sites mainly comprised migrants from other areas. The ovarian development level of females trapped using food attractants showed a positive correlation with the age of males, and there was also a significant positive correlation between the index of ovarian development of females and the mating time. Furthermore, a dynamic prediction method for fecundity in field populations was established based on the quantity of eggs held by the females. This study provides a new method for the monitoring and early warning of the existence of C. medinalis populations. [ABSTRACT FROM AUTHOR]

The damage symptoms of Cnaphalocrocis medinalis (C.medinalis) is an important evaluation index for pest prevention and control. However, due to various shapes, arbitrary-oriented directions and heavy overlaps of C.medinalis damage symptoms under complex field conditions, generic object detection methods based on horizontal bounding box cannot achieve satisfactory results. To address this problem, we develop a Cnaphalocrocis medinalis damage symptom rotated detection framework called CMRD-Net. It mainly consists of a Horizontal-to-Rotated region proposal network (H2R-RPN) and a Rotated-to-Rotated region convolutional neural network (R2R-RCNN). First, the H2R-RPN is utilized to extract rotated region proposals, combined with adaptive positive sample selection that solves the hard definition of positive samples caused by oriented instances. Second, the R2R-RCNN performs feature alignment based on rotated proposals, and exploits oriented-aligned features to detect the damage symptoms. The experimental results on our constructed dataset show that our proposed method outperforms those state-of-the-art rotated object detection algorithms achieving 73.7% average precision (AP). Additionally, the results demonstrate that our method is more suitable than horizontal detection methods for in-field survey of C.medinalis. [ABSTRACT FROM AUTHOR]

Global warming is posing a threat to animals. As a large group of widely distributed poikilothermal animals, insects are liable to heat stress. How insects deal with heat stress is worth highlighting. Acclimation may improve the heat tolerance of insects, but the underlying mechanism remains vague. In this study, the high temperature of 39 °C was used to select the third instar larvae of the rice leaf folder Cnaphalocrocis medinalis, an important insect pest of rice, for successive generations to establish the heat-acclimated strain (HA39). The molecular mechanism of heat acclimation was explored using this strain. The HA39 larvae showed stronger tolerance to 43 °C than the unacclimated strain (HA27) persistently reared at 27 °C. The HA39 larvae upregulated a glucose dehydrogenase gene, CmGMC10, to decrease the reactive oxygen species (ROS) level and increase the survival rate under heat stress. The HA39 larvae maintained a higher activity of antioxidases than the HA27 when confronted with an exogenous oxidant. Heat acclimation decreased the H2O2 level in larvae under heat stress which was associated with the upregulation of CmGMC10. The rice leaf folder larvae may acclimate to global warming via upregulating CmGMC10 to increase the activity of antioxidases and alleviate the oxidative damage of heat stress. [ABSTRACT FROM AUTHOR]

Insect tolerance to insecticides is closely related to the host plant. Migratory insects flying downwind and landing randomly may face host-plant switching after migration. However, it is not clear whether host-plant switching affects the tolerance of migratory insects to insecticides. In the present work, Cnaphalocrocis medinalis, a migratory pest destructive to rice, was studied to explore this issue. The results show that the host-plant switch reduced the susceptibility of rice and wheat larvae populations to abamectin but increased that of wheat larvae populations to chlorpyrifos, indicating that host switching resulted in different tolerance to different insecticides. Enzyme activity determination showed that, although abamectin and chlorpyrifos affect the activities of detoxification enzymes (carboxylesterase, multifunctional oxidase, and glutathione S-transferases), antioxidant enzymes (superoxide dismutase, peroxidase, and catalase), and acetylcholinesterase at sublethal dosages, the effect depends on the host plant and insecticide species. Overall, our findings show that the induction of C. medinalis by host switching affects its susceptibility and biochemical responses to abamectin and chlorpyrifos. Insecticides against C. medinalis should be used with consideration of the potential impact of host switching. Reasonable selection and usages of insecticides can help in the resistance management and control of migratory insects. [ABSTRACT FROM AUTHOR]

Premating behaviors mediated by pheromones play pivotal roles in animal mating choices. In natural populations of the striped stem borer Chilo suppressalis and the rice leaf roller Cnaphalocrocis medinalis in the rice field habitat, we discovered that Z11‐16:Ald, a major component of the C. suppressalis pheromone, modulated the premating behavior of C. medinalis. Z11‐16:Ald evoked a strong olfactory response in male antennae and strongly inhibited the sex pheromone trapping of male C. medinalis in the field. The functions of three C. medinalis sex pheromone receptor genes (CmedPR1–3) were verified through heterologous expression in Xenopus oocytes. CmedPR1 responded to Z11‐18:OH and Z11‐18:Ald, as well as the interspecific pheromone compound Z11‐16:Ac of sympatric species; CmedPR2 responded to Z13‐18:OH and Z13‐18:Ald, as well as the sex pheromone compounds Z11‐16:Ald and Z9‐16:Ald of sympatric species; and CmedPR3 responded to Z11‐18:OH and Z13‐18:OH, as well as the interspecific pheromones Z11‐16:OH, Z9‐16:Ald, Z11‐16:Ac, and Z11‐16:Ald of sympatric species. Thus, CmedPR2 and CmedPR3 share the ligand Z11‐16:Ald, which is not a component of the C. medinalis sex pheromone. Therefore, the sex pheromones of interspecific species affected the input of neural signals by stimulating the sex pheromone receptors on the antennae of male C. medinalis moths, thereby inhibiting the olfactory responses of the male moths to the sex pheromones. Our results demonstrate chemical communication among sympatric species in the rice field habitat, the recognition of intra‐ and interspecific sex pheromones by olfactory receptors, and how insect premating behaviors are modulated to possibly affect resource partitioning. [ABSTRACT FROM AUTHOR]

Different Cry toxins derived from Bacillus thuringiensis (Bt) possess different insecticidal spectra, whereas insects show variations in their susceptibilities to different Cry toxins. Degradation of Cry toxins by insect midgut extracts was involved in the action of toxins. In this study, we explored the processing patterns of different Cry toxins in Cnaphalocrocis medinalis (Lepidoptera: Crambidae) midgut extracts and evaluated the impact of Cry toxins degradation on their potency against C. medinalis to better understand the function of midgut extracts in the action of different Cry toxins. The results indicated that Cry1Ac, Cry1Aa, and Cry1C toxins could be degraded by C. medinalis midgut extracts, and degradation of Cry toxins by midgut extracts differed among time or concentration effects. Bioassays demonstrated that the toxicity of Cry1Ac, Cry1Aa, and Cry1C toxins decreased after digestion by midgut extracts of C. medinalis. Our findings in this study suggested that midgut extracts play an important role in the action of Cry toxins against C. medinalis, and the degradation of Cry toxins by C. medinalis midgut extracts could reduce their toxicities to C. medinalis. They will provide insights into the action of Cry toxins and the application of Cry toxins in C. medinalis management in paddy fields. [ABSTRACT FROM AUTHOR]

Odorant-binding proteins (OBPs) play important roles in the insect olfactory system since they bind external odor molecules to trigger insect olfactory responses. Previous studies have identified some plant-derived volatiles that attract the pervasive insect pest Cnaphalocrocis medinalis (Lepidoptera: Pyralidae), such as phenylacetaldehyde, benzyl acetate, 1-heptanol, and hexanal. To characterize the roles of CmedOBPs in the recognition of these four volatiles, we analyzed the binding abilities of selected CmedOBPs to each of the four compounds, as well as the expression patterns of CmedOBPs in different developmental stages of C. medinalis adult. Antennaes of C. medinalis adults were sensitive to the studied plant volatile combinations. Expression levels of multiple CmedOBPs were significantly increased in the antennae of 2-day-old adults after exposure to volatiles. CmedOBP1, CmedOBP6, CmedPBP1, CmedPBP2, and CmedGOBP2 were significantly up-regulated in the antennae of volatile-stimulated female and male adults when compared to untreated controls. Fluorescence competition assays confirmed that CmedOBP1 could strongly bind 1-heptanol, hexanal, and phenylacetaldehyde; CmedOBP15 strongly bound benzyl acetate and phenylacetaldehyde; and CmedOBP26 could weakly bind 1-heptanol. This study lays a theoretical foundation for further analysis of the mechanisms by which plant volatiles can attract C. medinalis. It also provides a technical basis for the future development of efficient plant volatile attractants of C. medinalis.

Cnaphalocrocis medinalis (Lepidoptera: Crambidae) is a migratory insect pest on rice crops. The migratory C. medinalis population in a particular location may be immigrants, local populations, emigrants, or a mix of these. Immigrants are strongly attracted to plant odor. We conducted research to identify the olfactory receptors in a floral scent mixture that is strongly attractive to C. medinalis. Through gene cloning, 12 olfactory receptor (OR) genes were amplified and expressed in Xenopus oocytes in vitro, and three of them were found to be responsive to plant foliar and floral volatiles. These were CmedOR31, a specific receptor for geraniol; CmedOR32, a broad-spectrum OR gene that responded to both foliar and floral odors; and CmedOR1, which strongly responded to 10−4 M phenylacetaldehyde. The electrophysiological response to phenylacetaldehyde was extremely high, with a current of 3200 ± 86 nA and an extremely high sensitivity. We compared the phylogenetic tree and sequence similarity of CmedOR genes and found that CmedOR1 belonged to a uniquely conserved OR pedigree in the evolution of Glossata species, and the ORs of this pedigree strongly responded to phenylacetaldehyde. The expression of OR1 was significantly higher in the females than in the males. Localization of CmedOR1 in the antennae of C. medinalis by fluorescence in situ hybridization showed that CmedOR1 was expressed in both males and females. CmedOR1 may be an odor receptor used by females to locate food sources. The function of these ORs and their role in pest monitoring were discussed.

Insect cuticle acts as a first line of defense and a physical protective barrier against entomopathogens. Chitin biosynthesis pathway plays a crucial role in chitin formation in the cuticle of insects. Glucosamine-6-phosphate N -acetyltransferase (GNA) is a key enzyme in insect chitin biosynthesis that regulate the chitin formation. However, how GNA-mediated cuticle metabolism influences virulence of entomopathogenic fungi is still unknown. In this study, CmGNA gene was cloned and characterized from the rice leaffolder Cnaphalocrocis medinalis. The CmGNA contains an open read frame (ORF) 600 nucleotides, encoding 199 amino acids with an isoelectric point of 8.65 and a molecular weight of 22.30 kDa. The expression profile showed that CmGNA was highly expressed in 4th instar larvae and in the cuticle. Here, we also reported the impact of CmGNA gene and entomopathogenic fungi, Metarhizium anisopliae and Beauveria bassiana, on expression pattern of chitin biosynthesis genes, feeding behavior, survival rate and average body weight of infected larvae, phenotypic deformities, rate of pupation, and adult emergence. Our results showed that knockdown of CmGNA and application of M. anisopliae and B. bassiana three days after RNA interference (RNAi) significantly decreased the expression of CmGNA and other associated genes, reduced feeding efficiency and survival rate, and caused loss of average body weight, less rate of pupation and adult emergence of infected larvae. Knockdown of CmGNA gene also increased the lethality of larvae caused by M. anisopliae and B. bassiana and resulted in significantly phenotypic deformities of infected larvae. Our findings illustrated that RNAi-mediated CmGNA knockdown disturbed the chitin synthesis genes that led to enhancing the virulence of M. anisopliae and B. bassiana , which can provide us new insights to develop novel biocontrol strategies against C. medinalis. [Display omitted] • CmGNA was characterized and expressed in 4th-instar larvae and cuticle. • Knockdown of CmGNA inhibited chitin synthesis and growth of C. medinalis. • Knockdown of CmGNA caused defective cuticle and aberrant phenotypes. • CmGNA knockdown enhanced virulence of entomopathogenic fungi against C. medinalis. [ABSTRACT FROM AUTHOR]

Salivary proteins in the oral secretion (OS) of chewing insects play a crucial role in insect-plant interactions during feeding. The rice leaf folder Cnaphalocrocis medinalis , a notorious pest in global rice production, triggers defense responses during feeding, but little is known about its salivary proteins. In this study, we confirmed that C. medinalis releases OS during feeding. By employing transcriptomic analysis and liquid chromatography-tandem mass spectroscopy (LC-MS/MS), we examined the salivary proteins from labial salivary glands and OS from C. medinalis. A total of 14,397 genes were expressed at the RNA level and 229 salivary proteins were identified. Comparative analysis with other 25 arthropod species revealed that 43 proteins were unique to C. medinalis. Expression pattern analysis revealed that most of the selected genes were highly expressed in the gut and the larval stages (4th–5th instar). These findings provide a comprehensive resource for future functional studies of salivary proteins, offering new insights into the molecular mechanisms by which C. medinalis modulates plant defenses and potential applications in pest management. [Display omitted] • The rice leaf folder Cnaphalocrocis medinalis release oral secretions when feeding on plants. • 229 salivary proteins were identified from C. medinalis oral secretions. • Salivary proteins from C. medinalis may be involved in digestion, immunity, detoxification, herbivore offense, etc. [ABSTRACT FROM AUTHOR]

In East Asia, rice is a key crop that is subject to significant insect driven crop damage often leading to wide scale reliance on insecticides. We assessed the effects of releasing conditions (including density, frequency and distribution points) of a parastic wasp (i.e., Trichogramma japonicum) on the control efficacy it provided against two rice pest herbivores (i.e., Chilo suppressalis and Cnaphalocrocis medinalis). Optimal control was achieved by three releases of 150,000 wasps per hectare across 75 release points within a hectare rice field. A following 2-year large-scale field experiment demonstrated that the release of parasitic wasps allowed a 60.0 % reduction in insecticide use when compared to the insecticide treatment alone. Importantly, there was also a 3.7 % increase in pest control, 2.5 % increase in rice yield, and an overall 4.5 % increase in net economic benefit when the release of parasitic wasps was combined with insecticide application. This was an improvement on the use of either parasitic wasps alone or insecticide application alone. Release of parasitic wasps had co-benefits for other invertebrate predators whose abundance was increased by 65.8 % relative to the insecticide only treatment, however, this fell to a 26.4 % increase when parasitic wasps release was combined with insecticide use. Additionally, the combined treatment group of parasitic wasps and insecticides exhibited the highest net economic benefit (40488.9±593.2 Chinese Yuan (CNY) ha−1), significantly surpassing both the parasitic wasps-only treatment by 8.9 % and the treatment of no parasitic wasps and no insecticide by 21.8 %. These findings suggest that parasitic wasps releasing is a feasible approach to ecological engineering to promote multiple ecosystem services linked to greater crop yield in agroecosystems. • Trichogramma japonicum wasps are natural enemies of rice pests. • An optimal strategy for releasing T. japonicum in eastern China is proposed. • T. japonicum and insecticide use maximizes pest control. • This increases yields leading to economic benefits. • T. japonicum without insecticide benefits other natural enemies. [ABSTRACT FROM AUTHOR]

With the widespread adoption of high yielding rice (Oryza sativa L.) varieties and accompanying changes in the cultural practices, rice leaf folder [Cnaphalocrocis medinalis (Guenee)] and yellow stem borer [Scirpophaga incertulas (Walker)] has attained the status of major pests and influence the yield if proper timely management practices are not adopted. For effective management of these pests, identification of new molecules with novel mode of action, low toxicity to non-target insects and environmental safety is required for sustainable IPM. Chlorantraniliprole 0.4% gr (Ferterra 0.4% gr) is an anthranillic diamide insecticide in granular form for the control of lepidopterous pests in rice. A field experiment was conducted to evaluate the efficacy of chlorantraniliprole 0.4% gr (Ferterra 0.4% gr) against rice leaf folder and yellow stem borer during rainy (kharif) seasons 2017–19. The study revealed that broadcast application of chlorantraniliprole 0.4% gr @40 g a.i./ha at tillering stage was found effective and best insecticidal treatment in reducing rice leaf folder and yellow stem borer infestation with no phytotoxicity symptoms and increased grain yield. Chlorantraniliprole 0.4% gr @40 g a.i./ha was also safer to the natural enemies of the rice ecosystem. Post-harvest residual analysis of chlorantraniliprole 0.4% gr was found below the limit of quantification, i.e. 0.01 ppm in rice grains, soil, paddy straw and husk at recommended and double of the recommended dose indicating its safety to human, animals and environment.

Copyright of Chinese Journal of Applied Entomology is the property of Chinese Journal of Applied Entomology, Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Applied Entomology is the property of Chinese Journal of Applied Entomology, Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Applied Entomology is the property of Chinese Journal of Applied Entomology, Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Applied Entomology is the property of Chinese Journal of Applied Entomology, Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: Cnaphalocrocis medinalis is one of the major rice insect pests in Asia. Chlorantraniliprole is one of the most important insecticides for the control of C. medinalis. In this study, a field-resistant population and a susceptible strain of C. medinalis were used to evaluate the inheritance of chlorantraniliprole resistance and fitness costs in the field., Results: The field-resistant population (Cm-RR) showed 128.4-fold resistance to chlorantraniliprole compared with the susceptible strain (Cm-SS). The dose-response of reciprocal cross progeny (F1 and F1') showed no significant difference, which indicated the inheritance of resistance to chlorantraniliprole in C. medinalis was autosomal. The degrees of dominance (D) of resistance for F1 and F1' were -0.19 and -0.05, respectively, indicating that the chlorantraniliprole resistance of C. medinalis was incompletely recessive inheritance. At the same time, significant differences between observed and expected mortalities of self-cross (F2 and F2') and backcross (BC and BC') progenies suggested chlorantraniliprole resistance is controlled by multiple genes. Furthermore, the Cm-RR population had a relative fitness of 0.32 with a substantially decreased pupation rate, emergence rate, fecundity, and substantially increased developmental time of larval and pupa stages., Conclusion: Current research showed that the inheritance of chlorantraniliprole resistance to C. medinalis was autosomal, incompletely recessive and multigene. The field-resistant population had a relative fitness of 0.32 when compared with the susceptible strain. This study provided valuable information for facilitating the development of chlorantraniliprole resistance management strategies. © 2024 Society of Chemical Industry., (© 2024 Society of Chemical Industry.)

Host plant resistance is very important in contrast of spraying insecticide to manage leaf folder, Cnaphalocrocis medinalis. From wide germplasm of rice, fifty rice landraces were screened and traits for resistance are characterized against leaf folder under natural climatic conditions. The occurrence % leaf damage showed significant variation and revealed the presence of resistance-susceptibility status among tested land races of rice. The infestation of leaf folder recorded significantly less in highly resistant landraces, viz. Rajboga, Kari kagga and Mapilai samba -1 (0.55-0.90%) in comparison to the highly susceptible genotypes, viz. GK -5, Krishna leela, Kaggalikearona, Bangaragandu, Kundipullan, Puttabatta-2 and Navara (66.03 to 74.77%). The correlation analysis revealed that plant height, length of flag leaf and panicle length had negative significant influence on the leaf folder % leaf damage infestation and offered resistance. The amount of total sugar and reducing sugars, free amino acids, nitrogen and phosphorus were recorded higher in the susceptible entries whereas, total phenols, potassium and tannins were found significantly higher in resistant genotypes.

The rice leaf folder, Cnaphalocrocis medinalis, is a significant migratory pest that restricts rice production in Asia and Africa, and monitoring and early warning measures are the basis for its management. Based on its regional migratory path in China, the pest population dynamics were monitored from 2020 to 2021 using food attractants. In this study, we also used internal reproductive system dissection to determine the adult age and reproductive developmental state. The monitoring results indicated that the trapping dynamics of C. medinalis males using food attractants and sex pheromones were approximately similar. Both trapping methods yielded C. medinalis males of different ages, with an identical age structure for both trap types. Dissection analysis of the reproductive system of females trapped using the food attractants indicated that in 2020, the population of C. medinalis in Liling, Hunan Province, was indigenous, while populations in other monitoring sites mainly comprised migrants from other areas. The ovarian development level of females trapped using food attractants showed a positive correlation with the age of males, and there was also a significant positive correlation between the index of ovarian development of females and the mating time. Furthermore, a dynamic prediction method for fecundity in field populations was established based on the quantity of eggs held by the females. This study provides a new method for the monitoring and early warning of the existence of C. medinalis populations.