Cnaphalocrocis Medinalis Research Articles

Identification and functional study of Fib-L, a major silk fibroin gene component in rice leaf folders.

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.

Seasonal incidence of rice leaf folder Cnaphalocrocis medinalis (Guenee) in rice at Kanpur Uttar Pradesh

Seasonal incidence of rice leaf folder Cnaphalocrocis medinalis (Guenee) in rice at Kanpur Uttar Pradesh

Understanding the Impact: Insect Pests of Millets and their Consequences on Yield Loss

Millets, crucial cereal crops in many regions, face significant threats from various insect pests, leading to substantial yield losses. Insect pests such as stem borers, leaf folders, aphids, midges, bugs, caterpillars, and termites inflict damage at different growth stages of millet plants. Stem borers like Chilo partellus and Sesamia inferens bore into stems, impairing structural integrity, while leaf folders such as Cnaphalocrocis medinalis create folded leaf shelters for feeding, causing extensive tissue damage. Aphids such as Rhopalosiphum maidis and shoot bugs like Peregrinus maidis extract sap, resulting in wilting and stunting of plants. Millet midges like Geromyia penniseti and Stenodiplosis sorghicola target reproductive structures, leading to grain abortion and reduced yield. Earhead pests like Cryptoblabes gnidiella and Helicoverpa armigera feed on developing grains, causing significant losses in quality and quantity. Additionally, termites like Odontotermes spp. and Microtermes spp. damage roots and stems, disrupting nutrient and water uptake causing plant death. Understanding the biology and ecology and implementing appropriate pest management strategies are crucial for mitigating yield losses and ensuring millet production sustainability.

Monitoring the leaf damage by the rice leafroller with deep learning and ultra-light UAV.

Rice leafroller is a serious threat to the production of rice. Monitoring the damage caused by rice leafroller is essential for effective pest management. Owing to limitations in collecting decent quality images and high-performing identification methods to recognize the damage, studies recommending fast and accurate identification of rice leafroller damage are rare. In this study, we employed an ultra-lightweight unmanned aerial vehicle (UAV) to eliminate the influence of the downwash flow field and obtain very high-resolution images of the damaged areas of the rice leafroller. We used deep learning technology and the segmentation model, Attention U-Net, to recognize the damaged area by the rice leafroller. Further, a method is presented to count the damaged patches from the segmented area. The result shows that Attention U-Net achieves high performance, with an F1 score of 0.908. Further analysis indicates that the deep learning model performs better than the traditional image classification method, Random Forest (RF). The traditional method of RF causes a lot of false alarms around the edge of leaves, and is sensitive to the changes in brightness. Validation based on the ground survey indicates that the UAV and deep learning-based method achieve a reasonable accuracy in identifying damage patches, with a coefficient of determination of 0.879. The spatial distribution of the damage is uneven, and the UAV-based image collecting method provides a dense and accurate method to recognize the damaged area. Overall, this study presents a vision to monitor the damage caused by the rice leafroller with ultra-light UAV efficiently. It would also contribute to effectively controlling and managing the hazardous rice leafroller. © 2024 Society of Chemical Industry.

Predicting possible distribution of rice leaf roller (Cnaphalocrocis medinalis) under climate change scenarios using MaxEnt model in China

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.

Knockdown of the glucosamine-6-phosphate N-acetyltransferase gene by RNA interference enhances the virulence of entomopathogenic fungi against rice leaffolder Cnaphalocrocis medinalis

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.

Efficacy of Various Insecticides against Leaf Folder Cnaphalocrocis medinalis (Guenee) in Rice and the Calculation of the Benefit-cost Ratio

The present investigation was conducted at Heera Puri research field, Institute of Agriculture and Natural Sciences, Deen Dayal Upadhyaya Gorakhpur University, Gorakhpur during Kharif, 2023. The relative effectiveness of six insecticides viz., Flubendiamide 39.35 % SC, Chlorpyriphos 20 EC, Acephate 95 SC, Chlorantraniliprole 18.5 SC, Fipronil 5 SC, Cartap hydrochloride 50% SP and Control. The study revealed that the treatment Flubendiamide 39.35% SC was found most effective followed by Chlorantraniliprole 18.5 SC, and Fipronil 5 SC whereas the highest infestation was recorded in the control plot. The significantly higher grain yield was obtained in Flubendiamide 39.35% SC treated plots which are followed by Chlorantraniliprole 18.5 SC, Fipronil 5 SC, Cartap hydrochloride 50% SP, Acephate 95 SC and Chlorpyriphos 20 EC. The highest increase in yield over control was reported in the plot treated with Flubendiamide 39.35% SC followed by Chlorantraniliprole 18.5 SC, Fipronil 5 SC, Cartap hydrochloride 50% SP, Acephate 95 SC, and Chlorpyriphos 20 EC. The economics of various treatments based on net profit and cost of plant protection revealed that. the highest cost: benefit ratio of Chlorpyriphos 20 EC was followed by Chlorantraniliprole 18.5 SC, followed by Acephate 95 SC, Fipronil 5 SC and the lowest benefit-cost ratio was reported in plots treated with Cartap hydrochloride 50% SP.

Physiological Status of Rice Leaf-Roller Cnaphalocrocis medinalis (Lepidoptera: Crambidae) Adults Trapped by Sex Pheromone and Floral Odor.

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.

Composition of Parasitoid Wasps in Insect Pests of Rice (Rice Leaffolder, Cnaphalocrocis Medinalis Guenée)

Biological control is one aspect of Integrated Pest Management (IPM). The method focusses on natural enemies; beneficial insects are applied for biological control of agricultural insect pests and also provide an environmentally friendly approach. For the rice pests including Rice Leaf Folder (RLF), several parasitoids tend to be natural enemies that could be used to control the pest from the egg stage to pupa. This study was conducted with two varieties of rice, namely “Sen Kra Oub” and “Sro Ngea” at Battambang Province of Cambodia. Parasitoid wasps were collected from egg to pupa stages of RLF and rice yellow stem borer by rearing method, and stored in 70% of alcohol solution before sending for identification in Vietnam’s Institute of Ecology and Biological Resources (IEBR) Laboratory. The outcomes revealed that five hymenopteran parasitic wasps of three different families were found, viz. Apanteles cypris Nixon, Bracon onukii Watanabe and Pentatermus striatus (Szepligeti) (Braconidae), Xanthopimla flavolineata Cameron (Ichneumonidae), and Telenomus rowani Gahan (Scelionidae) and being the primary parasitoids of rice leaffolder, Cnaphalocrocis medinalis Guenee; stemborer Scirpophaga incertulas Walker (Pyralidae) and black branded swift Pelopidas mathias (Hesperiidae). Parasitism was not found at the vegetative phase with Sen Kra Ob varieties but in reproductive phase. parasitism proportion was 16.66% and 28.57% to 50% in ripening phase, different from Sro Ngea variety where a proportion was found in vegetative phase 27.27%, reproductive phase at 28.57% to 40% and 28.57% to 43% in ripening phase. All the hymenopteran parasitoids were initially recorded in Cambodia, whereby all the parasitoids were potential agents for biological control for important rice insect pests. The outcome of this research suggests that the Government should invest more in the research and development for biological control in Cambodia.

CRY1 is involved in the take-off behaviour of migratory Cnaphalocrocis medinalis individuals

BackgroundNumerous 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.ResultsThe 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.ConclusionsThis study can help further explain the molecular mechanisms behind insect migration, especially light perception and signal transmission during take-off phases.

Heat-stress memory enhances the acclimation of a migratory insect pest to global warming.

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.

Brachymeria swaminathani sp. nov. (Hymenoptera, Chalcididae, Brachymeriinae) a new pupal parasitoid of rice leaf folder from southern India

A new species of the megadiverse cosmopolitan chalcidid genus Brachymeria Westwood (Chalcididae, Brachymeriinae), B. swaminathani is described with illustrations based on female specimens reared from pupae of rice leaf folder Cnaphalocrocis medinalis (Guenée) from southern India.

Differences in adult nutritional requirements impact the population growth and survival of two related species of rice leaffolders to produce interspecific differentiation

Nutrition is a limiting feature of species evolution. The differences in nutritional requirements are the evolutionary result of differential adaptations to environmental changes, explaining differences in their ecological traits. Cnaphalocrocis medinalis and Cnaphalocrocis exigua, two related species of rice leaffolders, have similar morphology and feeding properties but different migration and overwintering behaviors. However, it is unclear whether they have evolved adult nutritional differentiation traits to coexist. To explore this issue, this study examined the effects of carbohydrates and amino acids on their reproductive and demographic parameters. The findings indicate that carbohydrate intake prolonged the longevity and population growth of two rice leaffolders, but amino acid intake promoted egg hatching only. However, nutrient deficiency made it impossible for C. medinalis to reproduce successfully and survive, but it did not affect C. exigua. The population expansion and survival of migratory C. medinalis relied on adult nutritional intake. Conversely, the nutrients necessary for C. exigua overwintering activity mostly came from the storage of larvae. The difference in nutritional requirements for population growth and survival between the two rice leaffolders partially explained their differences in migration and overwintering.

Effects of adult diet on the longevity, fecundity and ovarian development of the rice leaffolder, Cnaphalocrocis medinalis

AbstractRice 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.

Field efficacy of newer insecticides against leaf folder (Cnaphalocrocis medinalis Gn.) in rice

Field efficacy of newer insecticides against leaf folder (Cnaphalocrocis medinalis Gn.) in rice

A parasitic wasp-releasing engineering to promote ecosystem services in paddy systems

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.

SURVEY OF LEPIDOPTERAN PESTS OF RICE ORYZA SATIVA L. FROM NAGALAND

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.. KEYWORDS :Cnaphalocrocis medinalis, Incidence, Leucania loreyi, Melanitis leda, Pests, Rice, Scirpophaga incertulas

Effective multidimensional treatment identification of different chemical fertilizers: Response of insect dynamics and rice production

Effective management of fertilizers is essential in influencing the prevalence of insects in rice (Oryza sativa L.) fields. Over two years (2019-20 and 2020-21), an experiment conducted at Bangladesh Rice Research Institute (BRRI), Habiganj, during the boro season aimed to identify the most effective multidimensional treatment (EMT) by testing various combinations of chemical fertilizers and its effect on rice insects. The goal was to optimize rice grain yield while minimizing harmful insect infestation and supporting natural enemies. Eight different chemical fertilizer applications were used as follows: T1 contained a full mix of nitrogen (N), phosphorus (P), potassium (K), and sulfur (S); T2 had PKS but lacked N; T3 had NKS but lacked P; T4 had NPS but lacked K; T5 had NPK but lacked S; T6 had KS but lacked N and P; T7 had PS but lacked N and K; and T8 lacked all four elements - N, P, K, and S.The relationship between the dynamics of harmful insects and natural enemies was highly positively correlated (r = 0.72 to 0.97). In two consecutive growing years, the 2020-21 season exhibited notably higher counts of harmful insects, with Rice Leafroller (RLR) dominating in the booting stage and White Backed Planthopper (WBPH) in mid-tillering, while Green Mirid Bug (GMB) prevailed among natural enemies across both stages, surpassing insect pest counts, notably GMB, Lady bird beetle (LBB), Carabid beetle (CDB), and Staphylinid (STD). However, the yield was notably higher in the 2019-20 growing season despite these pest pressures. Throughout the mid-tillering and booting stages, T1 consistently exhibited the highest average populations of harmful insects and natural enemies, while T7 demonstrated the lowest count of harmful insects, followed by T2 at both growth stages. Additionally, the highest grain yield (GY) was consistently recorded in T1, followed by T5, T6, and T3, with yields of 7.98 t/ha, 7.63 t/ha, 7.38 t/ha, and 7.33 t/ha, respectively. In both stages, beneficial insects prevailed over harmful ones in all fertilizer applications, with significant declines noted in T2 and T7. Factor analysis showed successful selection for EMT in the MGIDI index for all variables except INT and GY during the 2019-20 season, with selection differentials (SD) ranging from −0.10 to 8.29. However, in 2020-21, selection was achieved for all variables with SD ranging from 0.37 to 6.08. According to the MGIDI index, the top-ranked EMTs were identified as T4 and T3 for the 2019-20 period, and T3 and T5 for the 2020-21 period. The EMT shared in both years, T3, proved effective because of its positive impact on enhancing natural enemies throughout both periods (with SD ranging from 4.76 to 8.29 for 2019-20 and 3.03 to 6.08 for 2020-21), and its notable contribution to rice grain yield (SD = 0.37) in 2020-21. This study uniquely integrates EMT to optimize rice grain yield while simultaneously managing harmful insect infestations and supporting natural enemies, addressing a critical need in sustainable rice cultivation. The suggestion is to give preference to fertilizer application T3, which omits P but contains N and K, to improve rice grain yield and boost natural enemies, thereby reducing harmful insect infestation. Moreover, future investigations should concentrate on refining fertilizer blends to strike a harmony between maximizing yield and fostering ecological robustness in rice cultivation.

TSAF-Net: a rotated two-stage Cnaphalocrocis medinalis damage detection method based on anchor-free arbitrary-oriented proposal network.

Cnaphalocrocis medinalis (C.medinalis) is an agricultural pest with recurrent outbreaks. The investigation into automated pest and disease detection technology holds significant value for in-field surveys. Current generic detection methods are inadequate due to arbitrary orientations and a wide range of aspect ratios in damage symptoms. To tackle these issues, we put forward a rotated two-stage detection method for in-field C.medinalis surveys. This method relies on an anchor-free rotated region proposal network (AF-R2PN), bypassing the need for hyper-parameter optimization induced by predefined anchor boxes. An in-field C.medinalis dataset is constructed during on-site pest surveys to validate the effectiveness of our method. The experimental results show that our method can accomplish 80% average precision (AP), surpassing the corresponding horizontal detector by 2.3%. The visualization results of our work showcase its exceptional localization capability over generic detection methods, facilitating inspection by plant protectors. Meanwhile, our proposed method outperforms other state-of-the-art rotated detection algorithms. The AF-R2PN module can generate superior arbitrary-oriented proposals even with a decreased number of proposals, balancing inference speed and detection performance among other rotated two-stage methods. The proposed method exhibits superiority in detecting C. medinalis damage under complex field conditions. It provides greater practical applicability during in-field surveys, enhancing their efficiency and coverage. The findings hold significance for pest and disease monitoring, providing important technical support for agricultural production. © 2024 Society of Chemical Industry.

Cropland Microclimate and Leaf-nesting Behavior Shape the Growth of Caterpillar under Future Warming.

Predicting performance responses of insects to climate change is crucial for biodiversity conservation and pest management. While most projections on insects' performance under climate change have used macro-scale weather station data, few incorporated the microclimates within vegetation that insects inhabit and their feeding behaviors (e.g., leaf-nesting: building leaf nests or feeding inside). Here, taking advantage of relatively homogenous vegetation structures in agricultural fields, we built microclimate models to examine fine-scale air temperatures within two important crop systems (maize and rice) and compared microclimate air temperatures to temperatures from weather stations. We deployed physical models of caterpillars and quantified effects of leaf-nesting behavior on operative temperatures of two Lepidoptera pests: Ostrinia furnacalis (Pyralidae) and Cnaphalocrocis medinalis (Crambidae). We built temperature-growth rate curves and predicted the growth rate of caterpillars with and without leaf-nesting behavior based on downscaled microclimate changes under different climate change scenarios. We identified widespread differences between microclimates in our crop systems and air temperatures reported by local weather stations. Leaf-nesting individuals in general had much lower body temperatures compared to non-leaf-nesting individuals. When considering microclimates, we predicted leaf-nesting individuals grow slower compared to non-leaf-nesting individuals with rising temperature. Our findings highlight the importance of considering microclimate and habitat-modifying behavior in predicting performance responses to climate change. Understanding the thermal biology of pests and other insects would allow us to make more accurate projections on crop yields and biodiversity responses to environmental changes.