Brown Planthopper Populations Research Articles

Effects of imidacloprid combined with validamycin on the population fitness and symbiotic of Nilaparvata lugens (Hemiptera: Delphacidae)

Using a high-efficiency insecticide in combination with fungicides that have different mechanisms of action is a conventional method in the current management of brown planthopper (BPH) resistance. In this study, we investigate the separate and combined effects of the low-toxicity fungicide validamycin and the non-cross-resistant insecticide imidacloprid on the fitness and symbiosis of BPH. These research results indicate that when the proportion of active ingredients in validamycin is combined with imidacloprid at a ratio of 1:30, the toxicity ratio and co-toxicity coefficient are 1.34 and 691.73, respectively, suggesting that the combination has a synergistic effect on the control of BPH. The number of yeast-like symbiotic (YLS) and dominant symbiotic (Noda) in the imidacloprid + validamycin groups were significantly lower than the other three treatment groups (validamycin, imidacloprid, and water). The results of the study on population fitness show that the lifespan of the BPH population in validamycin, imidacloprid, and imidacloprid + validamycin was shortened. Notably, the BPH populations in the imidacloprid + validamycin groups were significantly lower than other groups in terms of average generation cycle, intrinsic growth rate, net reproduction rate, finite rate of increase, and fitness. The Real-time quantitative PCR showed that validamycin and imidacloprid + validamycin can significantly inhibit the expression of the farnesyl diphosphate farnesyl transferase gene (EC2.5.1.21) and uricase gene (EC1.7.3.3), with imidacloprid + validamycin demonstrating the most pronounced inhibitory effect. Our research results can provide insights and approaches for delaying resistance and integrated management of BPH.

Colonization of Piriformospora indica enhances rice resistance against the brown planthopper Nilaparvata lugens.

Piriformospora indica is an endophytic fungus that can promote the growth and confer resistance against diverse stresses in host plants by root colonization. However, the effects of P. indica colonization on improving plant resistance to insect pests are still less explored. The brown planthopper (BPH) Nilaparvata lugens is a serious monophagous pest that causes extensive damage to rice plants. Here, we aimed to evaluate the effects of P. indica colonization on rice resistance against BPH. The colonization of P. indica in rice roots resisted damage from BPH. Age-stage, two-sex life table analyses showed that feeding on P. indica-colonized rice plants affected BPH's female adult longevity, oviposition period, fecundity, population parameters and population size. BPH female adults feeding on P. indica-colonized plants excreted less honeydew. P. indica colonization remarkably increased the duration of np, N2, and N3 waveform, as well as the occurrences of N1 and N2, and decreased the duration of N4-b for BPH on rice plants. Meanwhile, the weight of BPH on the colonized plants was significantly lower than the control. In addition, the feeding and oviposition preferences of BPH to P. indica-colonized plants were reduced. qRT-RCR analyses revealed that P. indica colonization induced the expressions of jasmonic acid (JA)- and salicylic acid (SA)-related genes in rice plants. P. indica colonization can reduce BPH performance on rice plants with potential inhibitory effects on population growth. Collectively, these results support the potential for endophytically colonized P. indica as an effective strategy to improve insect resistance of crops. © 2024 Society of Chemical Industry.

A genomic investigation on the origins of the Korean brown planthopper, Nilaparvata lugens (Stål) (Hemiptera: Delphasidae)

AbstractNilaparvata lugens, the brown planthopper (BPH), is a serious pest species. BPHs cause significant damage to rice plants in Korea as well as other countries in East and Southeast Asia. As BPHs cannot survive winter in Korea, they annually migrate into Korea from foreign countries. The BPHs found in Korea are believed to originate from China, but most BPHs in China are also known to originate from Southeast Asia. To understand the origin of Korean BPHs, we conducted a genotyping‐by‐sequencing (GBS) study. We sampled BPHs from five locations in Korea and five countries in Southeast Asia and analyzed the GBS and sequencing results using various methods based on the f statistics and admixture graph analyses. We confirmed that the domestic BPHs shared a greater genetic drift than the BPHs from Southeast Asian populations over several years, implying that a continuous genetic substratum of Korea exists. This genetic substratum is genetically closer to BPHs from the southern part (Thailand and Cambodia) of Southeast Asia than to BPHs from the northern part (Bhutan, Myanmar and Laos) of Southeast Asia. In addition, direct gene flows from Southeast Asia seem possible, so Korea is considered a hotspot where diverse BPH populations mix. Therefore, the origin of Korean BPHs extends beyond China and as far as southern Southeast Asia. This result will help to understand and control the population dynamics of the Korean BPH population.

Symbiont Diversity in Imidacloprid-Resistant and Imidacloprid-Susceptible Populations of Nilaparvata lugens (Hemiptera: Delphacidae)1

Abstract Imidacloprid, a neonicotinoid insecticide, is efficacious against hemipterans, including the brown planthopper, Nilaparvata lugens (Stål) (Hemiptera: Delphacidae). However, frequent use of this insecticide has resulted in the development of high levels of resistance among brown planthopper populations. Endosymbionts of insects have contributed to host physiology and evolution and play a role in resistance to chemical toxins. In this study, polymerase chain reaction–denaturing gradient gel electrophoresis was used to analyze the bacterial and yeast-like symbiont communities of imidacloprid-resistant and -susceptible brown planthopper populations. The Shannon-Weaver diversity index and the evenness index indicated no differences in the richness and the expression of overall species distribution of the symbiotic communities of resistant and susceptible populations. The similarity coefficients of 0.53 and 0.56 for bacterial and yeast-like symbionts, respectively, indicated the main types of differences among microorganisms in resistant and susceptible populations. Sequence comparison analysis indicated the bacterial species in the susceptible population were members of the Enterobacteriaceae and Moraxellaceae, and those in the resistant population were members of the Enterobacteriaceae, Oxalobacteriaceae, Rhodobacteriaceae, and Sphingomonadaceae. Differences also were found in the composition of yeast-like symbionts of the two populations; Cryptococcus luteolus, Pseudozyma aphidis, and Pseudozyma antarctica were detected in the susceptible population, and Cladosporium perangustum was detected in the resistant population.

Combined miRNA and mRNA sequencing reveals the defensive strategies of resistant YHY15 rice against differentially virulent brown planthoppers.

The brown planthopper (BPH) poses a significant threat to rice production in Asia. The use of resistant rice varieties has been effective in managing this pest. However, the adaptability of BPH to resistant rice varieties has led to the emergence of virulent populations, such as biotype Y BPH. YHY15 rice, which carries the BPH resistance gene Bph15, exhibits notable resistance to biotype 1 BPH but is susceptible to biotype Y BPH. Limited information exists regarding how resistant rice plants defend against BPH populations with varying levels of virulence. In this study, we integrated miRNA and mRNA expression profiling analyses to study the differential responses of YHY15 rice to both avirulent (biotype 1) and virulent (biotype Y) BPH. YHY15 rice demonstrated a rapid response to biotype Y BPH infestation, with significant transcriptional changes occurring within 6 hours. The biotype Y-responsive genes were notably enriched in photosynthetic processes. Accordingly, biotype Y BPH infestation induced more intense transcriptional responses, affecting miRNA expression, defenserelated metabolic pathways, phytohormone signaling, and multiple transcription factors. Additionally, callose deposition was enhanced in biotype Y BPH-infested rice seedlings. These findings provide comprehensive insights into the defense mechanisms of resistant rice plants against virulent BPH, and may potentially guide the development of insect-resistant rice varieties.

Lethal competition on joint predators during suppressing brown planthopper population

Joint predator is one technique to control brown planthopper (Nilaparvata lugens) in the rice field by combining two or more predator species having a positive interaction. This study aims to determine the effect of joint predator density (Pardosa pseudoannulata and Phidippus sp) on competition and its predatory rate in suppressing the N.lugens population. The study used a completely randomized design (CRD) by combining P. pseudoannulata or Pp (1,2,3 individuals) and Phidippus sp or Ps (1,2,3 individuals) to become Pp1Ps1, Pp1Ps2, Pp1Ps3, Pp2Ps1, Pp2Ps2, Pp2Ps3, Pp3Ps1, Pp3Ps2, Pp3Ps3. The parameters observed were predation rate, bodyweight, mortality of both predators, and competition model. The results showed that the composition difference between P. pseudoannulata and Phidippus sp affected on competition model and the predation. The predation rate of joint predators at different densities ranged from 40.4 – 47.0 individuals of N.lugens (80.8-94.0%) in one-day observation, and they consumed all prey until the third day’s observation. The highest predation rate occurred for Pp3Ps3, but it was assumed it was not safe because of cannibalism and lethal competition. The Pp1Ps2 composition of joint predators was classified as safe, with 0 and 0.2 individuals’ mortalities and followed by draw competition between two predators.

Interactive effect of transplanting time and crop phenology on incidence of brown planthopper and spider population in rice (Oryza sativa)

Brown planthopper (BPH), Nilaparvata lugens (Stal 1854) is a destructive insect pest causing severe yield loss every year in rice (Oryza sativa L.) crop. An experiment was conducted during during kharif (rainy) seasons of 2021 and 2022 at the research farm of ICAR-Indian Agricultural Research Institute, New Delhi to study the effect of transplanting time and crop phenology on brown planthopper (BPH) incidence and spider population in rice. BPH and spider populations were recorded at different phenological stages in early, normal and late transplanted rice. Results showed that a significantly higher mean BPH population was observed in late transplanting in 2021 [54.00±5.31 per hill (nymphs and adults)] and 2022 (40.40±2.62 per hill) compared to normal and early tranplanting. Peak BPH population was observed at the heading (225.60±18.83 per hill) and milking stage (131.00±8.30 per hill) of late transplanted rice in 2021 and 2022, respectively. Likewise, more mean spider population was observed in late transplanting [1.87±0.11 per hill (adults) in 2021 and 2.38±0.08 per hill in 2022]. Two-way ANOVA showed a statistically significant interaction between transplanting time and crop phenology with regard to BPH incidence and spider population in both the years. The highest grain yield was recorded in early transplanted rice (36.08±0.75 q/ha; 35.06±0.49 q/ha) followed by normal (27.53±0.80 q/ha; 28.22±0.75 q/ha) and late transplanted rice crop (17.43±0.82 q/ha; 19.37±0.67 q/ha) respectively during two years. The early transplanted rice crop escaped the peak BPH incidence resulted in increased grain yield. The study demonstrated that both transplanting time and crop phenology influenced the BPH and spider populations.

Defense Regulatory Network Associated with circRNA in Rice in Response to Brown Planthopper Infestation

The brown planthopper (BPH), Nilaparvata lugens (Stål), a rice-specific pest, has risen to the top of the list of significant pathogens and insects in recent years. Host plant-mediated resistance is an efficient strategy for BPH control. Nonetheless, BPH resistance in rice cultivars has succumbed to the emergence of distinct virulent BPH populations. Circular RNAs (circRNAs) play a pivotal role in regulating plant–environment interactions; however, the mechanisms underlying their insect-resistant functions remain largely unexplored. In this study, we conducted an extensive genome-wide analysis using high-throughput sequencing to explore the response of rice circRNAs to BPH infestations. We identified a total of 186 circRNAs in IR56 rice across two distinct virulence groups: IR-IR56-BPH (referring to IR rice infested by IR56-BPH) and IR-TN1-BPH, along with a control group (IR-CK) without BPH infestation. Among them, 39 circRNAs were upregulated, and 43 circRNAs were downregulated in the comparison between IR-IR56-BPH and IR-CK. Furthermore, in comparison with IR-CK, 42 circRNAs exhibited upregulation in IR-TN1-BPH, while 42 circRNAs showed downregulation. The Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analysis revealed that the targets of differentially expressed circRNAs were considerably enriched in a multitude of biological processes closely linked to the response to BPH infestations. Furthermore, we assessed a total of 20 randomly selected circRNAs along with their corresponding expression levels. Moreover, we validated the regulatory impact of circRNAs on miRNAs and mRNAs. These findings have led us to construct a conceptual model that circRNA is associated with the defense regulatory network in rice, which is likely facilitated by the mediation of their parental genes and competing endogenous RNA (ceRNA) networks. This model contributes to the understanding of several extensively studied processes in rice-BPH interactions.

Ability of commercial Beauveria bassiana to suppress the brown planthopper attack by inducing resistance into different rice variety

Abstract. Liswandi A, Syahrawati M, Hamid H, Arneti, Rinaldi J. 2023. Ability of commercial Beauveria bassiana to suppress the brown planthopper attack by inducing resistance into different rice variety. Biodiversitas 24: 6704-6710. Beauveria bassiana (Bb) is one of the biological agents for controlling the Brown Planthopper (BPH), Nilaparvata lugens, which is generally applied directly to BPH. Nowadays, it is also used to induce resistance in rice plants; this ability has never been tested on commercial B. bassiana. The research aimed to study the effect of different rice varieties and induced resistance of commercial Bb on BPH and rice plants. The study used a Factorial Completely Randomized Design (FCRD). The first factor was the difference in rice varieties (IR 42, Cisokan, Batang Piaman), and the second factor was the soaking of the seeds and roots by commercial Bb (with commercial Bb, without commercial Bb). The results showed no interaction between rice variety and commercial Bb against BPH and rice plants. Commercial Bb reduced the attack intensity of BPH (13.31%); meanwhile, different rice varieties influenced BPH mortality, colonization, and plant growth. The Cisokan variety was better at suppressing the BPH population (45%) and suitable for colonization by commercial Bb. The IR 42 variety was more responsive than other varieties in accepting the presence of commercial Bb (16%).

Alanine metabolism mediates energy allocation of the brown planthopper to adapt to resistant rice

IntroductionDuring the adaptation to host plant resistance, herbivorous insects faced the challenge of overcoming plant defenses while ensuring their own development and reproductive success. To achieve this, a strategic allocation of energy resources for detoxification and ecological fitness maintenance became essential. ObjectiveThis study aimed to elucidate the intricate energy allocation mechanisms involved in herbivore adaptation that are currently poorly understood. MethodsThe rice Oryza sativa and its monophagous pest, the brown planthopper (BPH), Nilaparvata lugens were used as a model system. An integrated analysis of metabolomes and transcriptomes from different BPH populations were conducted to identify the biomarkers. RNA interference of key genes and exogenous injection of key metabolites were performed to validate the function of biomarkers. ResultsWe found that alanine was one of the key biomarkers of BPH adaptation to resistant rice variety IR36. We also found that alanine flow determined the adaptation of BPH to IR36 rice. The alanine aminotransferase (ALT)-mediated alanine transfer to pyruvate was necessary and sufficient for the adaptation. This pathway may be conserved, at least to some extent, in BPH adaptation to multiple rice cultivars with different resistance genes. More importantly, ALT-mediated alanine metabolism is the foundation of downstream energy resource allocation for the adaptation. The adapted BPH population exhibited a significantly higher level of energy reserves in the fat body and ovary when fed with IR36 rice, compared to the unadapted population. This rendered the elevated detoxification in the adapted BPH and their ecological fitness recovery. ConclusionOverall, our findings demonstrated the crucial role of ALT-mediated alanine metabolism in energy allocation during the adaptation to resistant rice in BPH. This will provide novel knowledge regarding the co-evolutionary mechanisms between herbivores and their host plants.

Epigenetic Diversity Underlying Seasonal and Annual Variations in Brown Planthopper (BPH) Populations as Revealed by Methylation- sensitive Restriction Assay.

The brown planthopper (BPH) is a monophagous sap-sucking insect pest of rice that is responsible for massive yield loss. BPH populations, even when genetically homogenous, can display a vast range of phenotypes, and the development of effective pest-management strategies requires a good understanding of what generates this phenotypic variation. One potential source could be epigenetic differences. With this premise, we explored epigenetic diversity, structure and differentiation in field populations of BPH collected across the rice-growing seasons over a period of two consecutive years. Using a modified methylation-sensitive restriction assay (MSRA) and CpG island amplification-representational difference analysis, site-specific cytosine methylation of five stress-responsive genes (CYP6AY1, CYP6ER1, Carboxylesterase, Endoglucanase, Tf2-transposon) was estimated, for identifying methylation-based epiallelic markers and epigenetic variation across BPH populations. Using a cost-effective and rapid protocol, our study, for the first time, revealed the epigenetic component of phenotypic variations in the wild populations of BPH. Besides, results showed that morphologically indistinguishable populations of BPH can be epigenetically distinct. Screening field-collected BPH populations revealed the presence of previously unreported epigenetic polymorphisms and provided a platform for future studies aimed at investigating their significance for BPH. Furthermore, these findings can form the basis for understanding the contribution(s) of DNA methylation in providing phenotypic plasticity to BPH.

Ecological engineering in low land rice for brown plant hopper, Nilaparvata lugens (Stål) management.

Rice field bunds and edges can act as near crop habitats, available for planting flowering plants to attract and conserve the natural enemies. We evaluated the effect of ecological engineering on the incidence of Brown Planthopper (BPH), Nilaparvata lugens (Stål)(Hemiptera; Delphacidae) and the abundance of its predators in the rice variety Pusa Basmati-1121. Plots included the oilseed crops viz. sesamum, sunflower and soybean, with plantings of flowering crops marigold, balsam and gaillardia as bund flora around the edges of rice plots. Ecologically engineered plots contained both crops+flowers and resulted in a significantly reduced BPH population per hill in rice plots for 2019 (6.3) and 2020 (9.4) compared to the control plots (9.8 and 14.4). Ecologically engineered plots also witnessed the delayed appearance of BPH during each growing season. Peak BPH populations are lower in the ecologically engineered plots than in the control grounds. Furthermore, the activity of natural enemies, viz., spiders, mirid bugs and rove beetles was the highest in rice fields planted with oilseed crops like sesamum, sunflower and soybean. Olfactory response studies showed that the attraction response of spiders toward sesamum and balsam leaves was more significant than in other crop plants. Rice yield was enhanced in plots planted with crops+flowers during both seasons compared to control plots. Planting of oilseed crops plants such as sesamum, sunflower and soybean with flowering crops such as marigold, balsam and gaillardia as bund flora on the bunds around the main rice field enhanced the natural enemy activity, suppressed the planthopper population, and increased yields. Based on the results, we recommend including ecological engineering techniques as one of the management components in the Integrated Pest Management programme for rice crops.

Rice brown planthopper monitoring and detection by spectral reflectance: a review

Brown planthopper (BPH) has been one of the main pests of rice worldwide. Monitoring is important factor for determining attacks and estimating their effects. The traditional monitoring approach is usually conducted through visual observation and field scouting, with limitations such as subjectivity and time consumption. Remote sensing is an alternative pest monitoring method that covers a larger area in a shorter time. This paper discusses a remote-sensing method that uses a spectral approach to detect BPH attacks. Literature was filtered and processed using the PRISMA method. According to the spectral sensor, studies were classified into multispectral and hyperspectral sensors. Based on this scale, there are four studies on the panicle, leaf, canopy, and field levels. The model used single-wave reflectance and spectral indices as predictors. Various algorithms were used in the studies: linear regression, Principal Component Analysis, and Machine Learning to estimate the severity class, BPH Population density, and yield loss. A combination of spectral reflectance with other parameters, such as weather, fertilizer application, and infestation time, was conducted to improve the performance of the detection model. This review provides state-of-the-art spectral reflectance usage for detecting BPH attacks and opportunities for future development.

Mitigation of Abiotic and Biotic Stress Using Plant Growth Regulators in Rice

Split plot design experiments were conducted to assess the performance of growth regulating compounds for mitigating moisture stress and the incidence of Brown Plant Hopper (BPH) in rice. The main plot treatments (4) comprised moisture stress free control (M1), moisture stress during panicle initiation stage alone (M2), moisture stress during flowering stage alone (M3), and moisture stress during both panicle initiation and flowering stages (M4). The sub-plot treatments (5) were foliar application of growth regulating compounds including chlormequat chloride at 200 ppm (S1), mepiquat chloride at 200 ppm (S2), brassinolide at 0.1 ppm (S3), pink pigmented facultative methylotrophs (PPFM) at 1% (S4), and no spray control (S5). The reduced plant growth attributes were registered under moisture stress at both panicle initiation and flowering stages. The spraying of 1% PPFM during the flowering or both at panicle initiation and flowering stages led to better performance than the other treatments. Also, spraying 1% PPFM brought down the population of BPH to a considerable level during both years of experiments. This suggests that spraying 1% PPFM in the post-flowering stage helps to mitigate the ill effect the moisture stress and BPH incidence.

Estimating insect pest density using the physiological index of crop leaf.

Estimating population density is a fundamental study in ecology and crop pest management. The density estimation of small-scale animals, such as insects, is a challenging task due to the large quantity and low visibility. An herbivorous insect is the big enemy of crops, which often causes serious losses. Feeding of insects results in changes in physiology-related chemical compositions of crops, but it is unknown whether these changes can be used to estimate the population density of pests. The brown planthopper (BPH), Nilaparvata lugens, is a serious insect pest hiding under rice canopy to suck the sap of rice stems. BPH density is a crucial indicator for determining whether the control using pesticides will be carried out or not. Estimating BPH density is still dependent on manmade survey and light-trap methods, which are time-consuming and low-efficient. Here, we developed a new method based on the physiological traits of rice leaves. The feeding of BPHs significantly decreased the contents of chlorophyll (the SPAD readings), water, silicon, and soluble sugar in rice leaves. Four ratio physiological indices based on these four physiological traits of the BPH-damaged rice leaves to those of healthy leaves were established, and they were significantly correlated with BPH density in rice plants. A rice growth stage-independent linear model based on the four ratio physiological indices and adding the other two variables, BPH damage duration and population increase rate, was developed. This model exhibited a reasonable accuracy for estimating BPH density. This new method will promote the development of density estimation of pest populations toward nonprofessionalization and automation.

Real-Time Contingency Measures as a Sustainable Strategy for Managing Biotic Stress in Rice Crop

Rice is grown in 2.0 lakh ha in Srikakulam district of Andhra Pradesh. Unpredictable weather conditions, low socio-economic status of farmers and various nutritional imbalances are the factors affecting the agricultural productivity in rain-fed agriculture in North coastal regions of Andhra Pradesh. With the effects of climate change, crops are sometimes affected by floods and sometimes by drought. Under such flood conditions, biotic stress including many fungal, bacterial, viral, nematode and non-parasitic diseases and among such diseases, blast, sheath blight are major and a limiting factors for the rice production. Considering these bottlenecks, KVK, Srikakulam assessed the realtime contingency measures against the biotic stress in rice crop at Kondavalsa and Ponnam villages of Srikakulam district in 2020 and 2021. Integrated pest and Disease management practices were implemented in real time against Blast, Sheathblight and BPH. The results showed that 70-75 per cent reduction in the incidence of blast among the management measures adopted plots in both the selected locations during 2020 and 2021. But only a 50% reduction was noted in the farmers approach. Similarly, PDI of Sheath blightwas reduced 78%. Also Brown plant hopper population was brought under control by using the management practices. In 2020, the grain yield of Kondavalasa and Ponnam villagesin the demo plots were 5580 and 5690 kg/ha at, respectively, while grain yield in farmers practice were 5090 and 5210 kg/, respectively. During 2021, demo plots at Kondavalasa and Ponnam also, recorded highest grain yields of 5630 and 5850 kg/ha, respectively. The higher severity of diseases like Blast, Sheath blight and pests such as, BPH has lead to poor yields in case of farmers approach. This study clears that adoption of certain measures viz., sowing of tolerant varieties, Seed treatment, Alleyways formation, optimized Nitrozen fertilizer application which promotes the better crop growth and reduce the occurrence of pests and diseases. Additionally, the timely spraying of highly efficient chemicals to control biological stresses such as Blast, Sheath blight and BPH will minimize crop yields and improved grains quality and quantity.

Effect of botanical insecticide application on the population of brown planthopper and its natural enemies and the growth and production of rice plants

Brown planthopper (Nilaparvata lugens Stall) is one of the most dangerous rice pests in Southeast Asia, therefor the population in the plantation must be controlled. This study aimed to determine the effectiveness of the botanical insecticide formulations in controlling brown planthopper attacks, the presence of natural enemies and their impact on the growth and production of rice plants. The study was conducted in the laboratory and the field. Screen house research was conducted in Indonesian Spices and Medicinal Crops Research Institute by testing the botanical insecticide formulation at five concentrations, namely; 0, 0.5, 2.5, 4.5, and 6.5 cc/l, and repeated five times. The results showed that at a concentration of 4.5cc/l, the insecticide was able to cause 97% mortality of the insects. This concentration was then used for spray application in the screen house which showed a more significant number of productive tillers, grain per bunch, and weight of 1000 grains than the control treatment, and about 25% higher in plant production. The Results of the field study conducted in Indramayu District showed that the botanical insecticide was able to suppress the population of N. lugens, but it was safe for natural enemies. The production of plants sprayed with botanical insecticides was 16.39% higher than the control treatment. This indicated that the botanical insecticide tested can be able to suppress the population of N. lugens, but was also safe against natural enemies and increase rice production.

Deep spatial and temporal graph convolutional network for rice planthopper population dynamic forecasting

Rice planthoppers (RPH) are important pests that cause severe yield losses in rice production in China. The widespread and intensive use of insecticides to prevent RPH causes serious issues. Forecasting the population dynamics of RPH is an important part of integrated pest management, which helps to prevent impending RPH outbreaks and reduce the use of insecticide. However, forecasting RPH population dynamics is very challenging as it results from complex spatial and temporal dispersion processes impacted by many factors, such as source populations, meteorological conditions, and host plant characteristics. Therefore, a novel deep learning-based model using graph convolutional network (GCN) and long short-term memory network (LSTM) is proposed in this study to capture RPH population dynamics. This model includes one dynamic GCN (DGCN) for modeling source populations and two attention-based LSTM encoder-decoder network (ALSTM) for modeling meteorological and host plants, respectively. The proposed model can dynamically aggregate the outputs of one DGCN and two ALSTM based on data to produce the final output for each county. The proposed model is evaluated on the dataset collected in South and Southwest China during 2000–2019, which includes populations, meteorological and host plant factors. The results demonstrate that DGCN-ALSTM outperforms other state-of-art deep learning methods and traditional time series forecasting approaches. The improvement brought by DGCN-ALSTM are about 1.95 %, 1.32 %, and 1.60 % for brown planthopper population, and 1.79 %, 0.71 %, and 0.32 % for white back planthopper population according to the R, RMAE, and RRMSE take DGCN as the baseline, respectively. The proposed DGCN-ALSTM provides a new better tool to forecast RPH population dynamics and the accurate forecasting results can guide local plant protection organizations to develop detailed sustainable pest control strategies and methods to control RPH in time.

Population Dynamic of Brown Plant Hopper, Predators and Neutral Insects in Irrigated Rice of Yogyakarta after Insecticides Application

Brown Plant Hopper (BPH) infestation in irrigated rice agroecosystem resulted yield loss. The application of insecticides by farmers are usually excessive, reducing pest population and negatively affecting the predators. This research aimed to define the impact of insecticides on the population dynamic of BPH, predator and neutral insects which influenced rice yield. Research was conducted at Yogyakarta, Indonesia, during May to September 2021. Randomized Block using four replications was applied. Rice varieties Inpari 32 HDB and Inpari 42 GSR were planted. Insecticide with active ingredient spinetoram 120 g/l and triflumezopyrim 106 g/l were applied to the rice plant on day 40th then pimetrozin 50% was applied at day 50th. Results showed that BPH population was reduced from 30-50 nymph per 30 plants to 10 nymph at day 12th after pimetrozin 50% application or at the day 2nd after spinetoram and triflumezopyrim insecticides application until day 50th. In contrast, BPH population in all insecticide plants was significantly lower than in all control and did not increase until harvest. On the other side, predators such as Paederus sp and Coccinelids were not affected by all insecticides, except Ophionea sp, Spiders and Cythorinus sp. However, their population recovered at day 30th after first insecticides application. Within the fluctuated population of BPH, rice productivity of Inpari 32 HDB and Inpari 42 GSR applied with insecticides were 9.52 ton ha-1 and 10.60 ton ha-1, while Inpari 32 HDB control and Inpari 42 GSR control 9.44 ton ha-1 and 10.72 ton ha-1

Sensitivity Test of Nilaparvata lugens Stall to Pymetrozine Insecticide

Brown planthopper (BPH) Nilaparvata lugens Stall is a major pest of rice that often causes outbreaks in several rice production centers in Indonesia. The use of insecticides is still the choice of farmers to control attacks due to weak mitigation efforts in an area. Continuous use of insecticides can increase the resistance and resurgence of BPH. The purpose of this study was to determine the level of sensitivity of the BPH population to the pimetrozine insecticide. The research was conducted at Assesment and Research Instalation of Agricultural Technology Ungaran, Assesment Institute of Agricultural Technology Central Java, Semarang Regency, Central Java, Indonesia from October 2019 to June 2020. The BPH population was collected from five regions, namely Jaten and Bolong Districts, Sukoharo District, and Bendosari, Mojolaban and Pulokarto Districts, Karanganyar District. The method of sensitivity test of BPH to insecticides was carried out according to the IRAC method number 005. Observations were made on the percentage of BPH mortality. The data was processed using Probit analysis to determine the LC50 value. The LC50 value was used to determine the resistance factor (RF). The results showed that the population of BPH Bolong Karanganyar was the most sensitive to the insecticide pymetrozine with an LC50 value of 13.44 ppm. The populations of BPH Jaten, Bolong, Bendosari, Mojolaban and Pulokarto were not resistant to pymetrozine insecticide due to the level of RF was ≤4. The population of BPH Pulokarto Sukoharjo with an RF value of 2.47 has the potential to become more resistant to the insecticide pymetrozine. It is necessary to periodically monitor the resistance of BPH to pymetrozine insecticides in the Karanganyar and Sukoharjo areas to prevent further resistance development.