Major Pest Of Rice Research Articles

Development and Temperature-induced Expression of a HSP90 Gene Lacking Introns in Cotesia chilonis (Hymenoptera: Braconidae)

Abstract Cotesia chilonis (Munakata) is the predominant parasitic wasp of Chilo suppressalis Walker (Lepidoptera: Pyralidea), a major rice pest in China. As climate change continues to intensify, C. chilonis and C. suppressalis must adapt to the increased frequency of adverse temperatures. In this study, the novel Cchsp90-2 was isolated and characterized from C. chilonis. The full-length Cchsp90-2 cDNA was 2689 bp and encoded 728 amino acids with an isoelectric point of 4.93. Cchsp90-2 encodes three heat shock protein 90 (HSP90) family signatures, and the alignment of genomic and cDNA sequences revealed that Cchsp90-2 does not contain introns. Real-time quantitative PCR revealed that Cchsp90-2 was induced in eggs and adults; however, larvae and pupae showed no significant differences in Cchsp90-2 expression levels. Cchsp90-2 was induced at both high and low temperatures, with very high expression levels after a 2-h exposure to 33°C or −13°C. This study provides insight into the mechanistic basis of thermal tolerance in C. chilonis and has implications for deploying this wasp to control C. suppressalis.

Variation in the stored grain pest Sitotroga cerealella (Olivier) infestation at low and high moisture storage conditions among some indigenous rice genotypes of West Bengal

The food security programme is negatively impacted by postharvest losses (PHLs). In terms of providing food for a nation, proper grain postharvest (PHV) storage is more crucial than intense and widespread farming. Reducing post-harvest losses of food crops is essential to raising agricultural production sustainably. Each year, insects and diseases destroy or harm a fifth or more of stored food grains in many regions of the world. The angoumois grain moth, Sitotroga cerealella (Oliver), is a major stored grain pest of rice. Control of Sitotroga cerealella (Olivier) is still much dependent on the use of toxic chemicals though there is a chance of residual toxicity to the non-target organism. Rice, wheat, and corn are just a few examples of grains that are crucial to the economic stability of many nations. Cereals like rice, wheat and corn play an important role in the economic stability of many countries. Some indigenous rice varieties of rice are reported to be tolerant of this pest. This study was undertaken to identify West Bengal indigenous rice varieties susceptible to the stored grain pest S. cerealella infestation at low and high moisture storage conditions.

Progress in exploitation and utilization of brown planthopper resistance gene in rice

<p indent="0mm">Rice is the most important food crop globally and a model species for basic biological research. Brown planthopper (BPH) is one of the major insect pests of rice. In the past decades, scientists have explored the BPH resistance gene from rice germplasm and revealed the molecular mechanism underlying the host plant resistance of rice to BPH. Research results have promoted the development of BPH-resistant rice varieties and their release in rice production. This review briefly introduces the research progress on brown planthopper resistance gene discovery, mechanism analysis, germplasm innovation, and utilization in rice breeding programs to help readers understand the mystery of plant resistance against insects and the practical significance of insect resistance research in plants.

Heritable Epigenomic Modifications Influence Stress Resilience and Rapid Adaptations in the Brown Planthopper (Nilaparvata lugens).

DNA methylation in insects is integral to cellular differentiation, development, gene regulation, genome integrity, and phenotypic plasticity. However, its evolutionary potential and involvement in facilitating rapid adaptations in insects are enigmatic. Moreover, our understanding of these mechanisms is limited to a few insect species, of which none are pests of crops. Hence, we studied methylation patterns in the brown planthopper (BPH), a major rice pest, under pesticide and nutritional stress, across its life stages. Moreover, as the inheritance of epigenetic changes is fundamentally essential for acclimation, adaptability, and evolution, we determined the heritability and persistence of stress-induced methylation marks in BPH across generations. Our results revealed that DNA methylation pattern(s) in BPH varies/vary with environmental cues and is/are insect life-stage specific. Further, our findings provide novel insights into the heritability of stress-induced methylation marks in BPH. However, it was observed that, though heritable, these marks eventually fade in the absence of the stressors, thereby suggesting the existence of fitness cost(s) associated with the maintenance of the stressed epigenotype. Furthermore, we demonstrate how 5-azacytidine-mediated disruption of BPH methylome influences expression levels of stress-responsive genes and, thereby, highlight demethylation/methylation as a phenomenon underlying stress resilience of BPH.

Effect of Insecticide Application Rates on Population Density of Orseolia oryzivora in Relation to its Parasitoids on Rice

Africa rice gall midge (Orseolia oryzivora) is a major insect pest of rice and the use of insecticides in its control poses danger to the environment and destroys biodiversity. The experiment was conducted to evaluate effect of lambda-cyhalothrin and carbofuran rates on population density of O. oryzivora in relation to its parasitoids on rice. The treatments were arranged in split-plot and fitted in to Randomized Complete Block Design, replicated three times. Observations were made on tiller number per hill, plant height, days to 50% flowering, % incidence, % severity, % parasitism of O. oryzivora, panicle /m2, grains / panicle and yield of rice. Data collected were subjected to Analysis of Variance and significant means were separated using Least Significant Difference (LSD) at p&lt;0.05. The result showed that Rice plants treated with lambda-cyhalothrin at rate of 1L/ha, 0.75 L/ha, Carbofuran at rate of 10.0 kg/ha and 7.5 kg/ha had higher yield (2.90-2.97 tonnes/ha) compared with control (2.55 tonnes/ha). They also had lowest incidence (2.09-2.64%) and severity (2.40-3.72%) of O. oryzivora compared with 8.26-17.17% and 9.93- 14.72% in plants treated with lambda-cyhalothrin at 0.50 L/ha and control respectively. The parasitism of O. oryzivora was high on rice plants treated with Carbofuran and the untreated ones (1.16-1.74) compared with other application of lambda-cyhalothrin.

Improved crop protection and biodiversity of the agroecosystem by reduced tillage in rice paddy fields in southern China

Agricultural sustainability has benefited from the broad adoption of conservation agriculture (CA) practices for decades, in which the reduction of mechanical disturbances to soil (also known as reduced tillage, RT) is one of the most essential principles for CA implementation. Many studies have recommended the advantages of CA practices in the promotion of biodiversity, but the integrated impacts on crop productivity and biodiversity remain unclear. Since CA has been applied in rice production in the subtropical area of southern China for several years, the effects of CA, particularly the RT methods, need to be evaluated for the local and long-term adoption. In this study, we established an integrated network to illustrate how the reduction of tillage intensity influenced organisms including invertebrates (such as rice pests and their predators), pathogens and weeds, and then led to an impact on rice yield. The two-year study demonstrated that major rice pests, such as rice planthoppers, stem borers and apple snails, were effectively controlled by RT practice. Similarly, the occurrence of common diseases declined with less tillage. Compared to the conventional tillage (CT) treatment, the density of weeds in paddy fields deceased significantly in the RT treatment. In addition, the diversity and richness of pest predators increased remarkably in paddy fields where either reduced or no tillage was applied, which highlighted the significance of a CA strategy for the promotion of biodiversity in the agroecosystem. More importantly, the rice yield gradually increased after the two-year reduction of tillage. Taken together, our results suggest that the reduction of tillage intensity is beneficial for the protection of rice crops from various pests, and facilitates the sustainability of the agroecosystem and rice yield, which provides a solid basis and novel insights for the establishment of sustainable agroecosystems by CA-related practices in rice production in southern China.

Optimizing the capture of neophobic rice field rats in lowland Asian rice ecosystems

BACKGROUNDTrapping is a key method for monitoring small mammals and is also one of a number of methods recommended under an ecologically‐based rodent management program to control rodent pest populations. Live‐traps are widely used globally for studying small mammal populations. In Asia where rodents are major pests of rice, single capture traps typically provide low trap success. We compared the trap success between two types of live‐traps in rice fields in Indonesia and the Philippines.RESULTSMultiple‐capture traps (MCTs) in conjunction with a linear trap barrier were significantly more effective in catching rodent pest species than single‐capture traps (SCTs) in Indonesia and the Philippines. In Indonesia, MCTs captured more individuals with a mean (±SE) percent trap success rate of (15.54 ± 4.29) compared to SCTs (3.88 ± 1.58). In the Philippines, MCTs captured more species of rodents and had a significantly higher recapture rate (1.96 ± 0.79), than SCTs (0.58 ± 0.32).CONCLUSIONMultiple‐capture traps with a linear trap‐barrier were more effective for capturing Rattus argentiventer and Rattus tanezumi in rice field ecosystems compared to single‐capture traps. MCTs captured more species of rodent pests in the Philippines and recaptured more individuals of each species. These results indicate that rodent populations can be more effectively monitored and controlled by using a multi‐capture trap with barrier system than the use of single capture traps on their own. This is the first time these two trap types have been compared for use in rice ecosystems in Asia. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Novel Formulation of Herbal Pesticide for Rice Cultivation

The irrational use of chemical pesticides has caused serious health hazards and environmental problems in developing countries including India. Hence, the Present investigation was carried out to formulate an effective Herbal pesticide against three major pests of rice like stem borers, leafhoppers and plant hoppers and to find solution for control of pest population by traditional agricultural practices. Oil of Azadirachta indica, Vitex nigundo, Ipomoea carnea, Adhatoda zeylanica and natural surfactant are the main constituents used in the formulations. Larvae of stem borers in the infected stem and hopper damaged part of the plant were selected for the study. A total of six herbal formulations at four different concentrations were sprayed on larvae of stem borers and hopper damaged parts of plants. The developed herbal pesticides have been validated in the field as well as in lab conditions and larval mortality rates were observed. After treatment, the population of pests decreased gradually and the mortality rate of larvae increased. Herbal pesticides focus on providing solutions and relief from various types of insects that cause massive damages to the plants being grown on a farm. These products were made of natural materials that have properties of killing or keeping out pests within the range of the field. The results showed that the extent of growth of these pests was less when compared to control and minimum occurrence of pest attack and Percent Dead Heart (DH) was confirmed in response to herbal formulations. The foremost benefit of this herbal pesticide is managing the Yellow Stem Borer (YSB) pest population and providing healthier cropping systems. Hence it is recommended to use this herbal pesticide for disease free sustainable cultivation of organic rice.

Novel Formulation of Herbal Pesticide for Rice Cultivation

The irrational use of chemical pesticides has caused serious health hazards and environmental problems in developing countries including India. Hence, the Present investigation was carried out to formulate an effective Herbal pesticide against three major pests of rice like stem borers, leafhoppers and plant hoppers and to find solution for control of pest population by traditional agricultural practices. Oil of Azadirachta indica, Vitex nigundo, Ipomoea carnea, Adhatoda zeylanica and natural surfactant are the main constituents used in the formulations. Larvae of stem borers in the infected stem and hopper damaged part of the plant were selected for the study. A total of six herbal formulations at four different concentrations were sprayed on larvae of stem borers and hopper damaged parts of plants. The developed herbal pesticides have been validated in the field as well as in lab conditions and larval mortality rates were observed. After treatment, the population of pests decreased gradually and the mortality rate of larvae increased. Herbal pesticides focus on providing solutions and relief from various types of insects that cause massive damages to the plants being grown on a farm. These products were made of natural materials that have properties of killing or keeping out pests within the range of the field. The results showed that the extent of growth of these pests was less when compared to control and minimum occurrence of pest attack and Percent Dead Heart (DH) was confirmed in response to herbal formulations. The foremost benefit of this herbal pesticide is managing the Yellow Stem Borer (YSB) pest population and providing healthier cropping systems. Hence it is recommended to use this herbal pesticide for disease free sustainable cultivation of organic rice.

DEVELOPMENT OF BIOINSECTICIDES AGAINST SPODOPTERA FRUGIPERDA USING CHITINOLYTIC BACTERIA

Actinomycetes play an important role in the biological control of insects by producing insecticidal active compounds against various insects. They are predominantly found in soil, in the silt of water bodies, in the air and in plant remains. Chitinase is increasingly finding applications in various fields such as biomedicine, in ultra-structural studies, in the preparation of chitooligosaccharides, in single-cell protein production, biocontrol agents, agriculture, etc. Chitinase is originally an enzyme used by insects to degrade the structural polysaccharide of insects. Chitinase brings about hydrolysis of chitin which is widely distributed in cell wall of fungi, plants and insects. An attempt has been made to use chitinase producing bacteria for the development of bioinsecticides against Spodoptera frugiperda, which feeds on over more than 60 species of plants and it is periodic. The Spodoptera frugiperda armyworm (Lepidoptera) is a serious pest of cabbage and other crop. It is also major pest of maize, rice, sorghum, turf grasses, cotton, and peanuts, etc. In this attempt enrichment and isolation of chitinase producing bacteria from soil was carried out. Chitinolytic activities of the three isolates were tested against larvae of Spodoptera frugiperda. Three isolates were individually applied against Spodoptera frugiperda. The isolates named Ai, A2 and A3 were found to be more effective against Spodoptera frugiperda. The insecticidal activity of isolate A1was tested and control within 5 hours. Isolate A2 was treated with larvae Spodoptera frugiperda killed after 8 hours whereas, isolate A3 controlled after 24 hours. The evaluated insecticides provided a significant reduction in the infestation level, for variable periods.

Efficiency of a Novel Light-Emitting Diode (LED) Trap for Trapping Rhyzopertha dominica (Coleoptera: Bostrichidae) in Paddy Rice Storehouses.

The lesser grain borer Rhyzopertha dominica is the major pest of stored paddy rice globally, including in Taiwan. It has strong phototaxis and is good at flying, suitable for developing a light-trapping method to monitor and control it. In the present study, a wavelength of light-emitting diodes (LEDs), i.e., 373 nm, was determined to be the most efficient to trap R. dominica using a dodecagon maze. Accordingly, an LED trap, named the Taiwan Agricultural Research Institute-LED (TARI-LED) trap, was invented, which comprised LEDs of two distinct wavelengths (373 and 408 nm), a wavelength switch, a suction fan, and an insect collector. The trapping efficiency was assessed in a 4-m3 laboratory arena and two paddy rice storehouses. An initial assessment was performed in the laboratory arena and showed that the TARI-LED trap with 373-nm wavelength for R. dominica rapidly increased in the first 30 min, reaching the highest trapping rate (68.5%) after 3 h. In addition, no significant difference was observed between the suction fan turned on or off. The field tests showed that the 373-nm wavelength had the highest effectiveness for trapping R. dominica in the two paddy rice storehouses, and no significant difference was observed in the number of R. dominica trapped by the 373-nm TARI-LED trap or the CDC-UV light trap. In conclusion, our TARI-LED trap 373 nm exhibited high efficiency in trapping R. dominica in paddy rice storehouses. Moreover, a suction fan-free design should benefit long-term and safe use in paddy rice storehouses trapping R. dominica.

Downregulation of the CsABCC2 gene is associated with Cry1C resistance in the striped stem borer Chilo suppressalis

Chilo suppressalis is a major target pest of transgenic rice expressing the Bacillus thuringiensis (Bt) Cry1C toxin in China. The evolution of resistance of this pest is a major threat to Bt rice. Since Bt functions by binding to receptors in the midgut (MG) of target insects, identification of Bt functional receptors in C. suppressalis is crucial for evaluating potential resistance mechanisms and developing effective management strategies. ATP-binding cassette (ABC) transporters have been vastly reported to interact with Cry1A toxins, as receptors and their mutations cause insect Bt resistance. However, the role of ABC transporters in Cry1C resistance to C. suppressalis remains unknown. Here, we measured CsABCC2 expression in C. suppressalis Cry1C-resistant (Cry1C-R) and Cry1C-susceptible strains (selected in the laboratory) via quantitative real-time PCR (qRT-PCR); the transcript level of CsABCC2 in the Cry1C-R strain was significantly lower than that in the Cry1C-susceptible strain. Furthermore, silencing CsABCC2 in C. suppressalis via RNA interference (RNAi) significantly decreased Cry1C susceptibility. Overall, CsABCC2 participates in Cry1C mode of action, and reduced expression of CsABCC2 is functionally associated with Cry1C resistance in C. suppressalis.

Comparative efficacies of modules against major insect pests and natural enemies in rice (Oryza sativa)

A field experiment was conducted at regional Research and Technology Transfer Station (OUAT), Chiplima,Sambalpur, Odisha, during rainy season (kharif) 2019–20 to determine the comparative efficacies of variousinsecticides and botanicals modules against major insect pests and natural enemies of rice (Oryza sativa L.). Therewere 9 modules and overall data revealed that the all the treated plots recorded significantly lower per cent of deadheart; white ear-head caused by stem borer; silver shoot caused by gall midge; leaf folder infested leaves and planthoppers. Among them, module consists of fipronil 5 sc @1500 ml/ha at 25–30 DAT, rynaxypyr 20 sc @150 ml/ha at45–50 DAT and triflumezopyrim 106 sc @240 ml/ha at 65–70 DAT treated plot recorded significantly higher per centreduction of stem borer infestation, leaf folder, plant hoppers and produced higher grain yield than the other modules as well as highest benefit cost ratio B : C (1.89) and next best was carbosulfan 25 ec @875 ml/ha, rynaxypyr 20 sc @150 ml/ha and flonicamid 50 wg @150 g/ha containing module. So, the module containing fipronil, rynaxypyr and triflumezopyrim may be adopted for the effective management of major insect pests of rice and helps the farmers from unwanted spraying of insecticides many times.

Population Genetic Structure of Chlorops oryzae (Diptera, Chloropidae) in China.

Simple SummaryRecently, Chlorops oryzae has become one of the major pests of rice in some regions, which has caused serious economic losses. To understand the genetic mechanisms of frequent local outbreaks and population expansion of C. oryzae, we analyzed the population genetic structure using two molecular markers, COI and ITS1 sequences. The results indicated that the C. oryzae populations experienced rapid expansion after a “Bottleneck effect” and the local outbreaks were probably caused by frequent gene flow among populations.Frequent outbreaks have made Chlorops oryzae one of the major pests of rice in some regions. In order to understand the ecological adaptation of C. oryzae at the molecular level, and provide a scientific basis for formulating management strategies, we used two molecular markers, COI and ITS1 sequences, to systematically analyze the genetic structure of 31 populations. The higher haplotype diversity and lower nucleotide diversity indicated that the C. oryzae populations experienced rapid expansion after a “Bottleneck effect”. The results of the mismatch distribution, neutrality test (Fu’s Fs < 0, p < 0.001), and haplotype network analysis suggested that the population has recently undergone an expansion. Although genetic differentiation among C. oryzae populations was found to have existed at low/medium levels (Fst: 0.183 for COI, 0.065 for ITS1), the frequent gene flow presented as well (Nm: 2.23 for COI, 3.60 for ITS1) was supposed to be responsible for frequent local outbreaks.

Tolerance against brown planthopper (Nilaparvata lugens) in wild rice (Oryza sativa) accessions

Brown planthopper, Nilaparvata lugens (Stål), is a major insect pest of rice in all the rice growing areas of the world. In the present study, the tolerance mechanism of resistance in wild rice accessions belonging to different Oryza species such as O. nivara (IRGC104646, CR100204), O. australiensis (IRGC105275, IRGC105270), O. punctata (IRGC99577) along with resistant check, Ptb33 and susceptible check, TN1 has been studied. The experiments were carried out on 30-days old plants under glasshouse conditions during kharif 2017 and 2018. IRGC99577 (22.80 and 24.00) took maximum days to hopper burn condition during both seasons. Functional plant loss index (%) was minimum in IRGC99577 (18.10%) followed by Ptb33 (20.96%) and IRGC104646 (29.47%). Least plant dry weight loss index (mg) was observed in Ptb33 and highest in TN1 during both the seasons. Overall, results indicated that rice accessions, IRGC99577 and IRGC104646 showed high levels of tolerance as compared to other wild rice accessions that were tested. The identified accessions thus could serve as potential sources of resistance in breeding BPH resistant varieties.

Effects of sublethal concentrations of cyantraniliprole on the biology and metabolic enzyme activities of Laodelphax striatellus (Fallén)

Cyantraniliprole has been widely used in China for controlling many pests, including the small brown planthopper (SBPH) Laodelphax striatellus (Fallén), which is a major pest of rice. Sublethal effects of cyantraniliprole on SBPH have not yet been examined. In this study, 3rd instar nymphs of SBPH were exposed to the LC10, LC20, and LC30 (3.17, 6.07, and 9.70 mg/L) of cyantraniliprole, which led to reductions in survival rate and hatchability of the F0 generation. Compared with the control, sublethal concentrations of cyantraniliprole significantly prolonged the development time of the 4th and 5th instar nymphs of the F1 generation. In the LC10, LC20, and LC30 treatment groups, the nymphal duration was prolonged by 1.98, 0.99, and 2.54 d, respectively. In addition, the sublethal concentrations of cyantraniliprole shortened the adult preoviposition period. The activities of cytochrome P450 monooxygenases and carboxylesterase in SBPH were promoted after treatment with sublethal concentrations of cyantraniliprole. The increase in insecticide resistance may be due to the increase in the activity of detoxification enzymes. Therefore, this research can provide a theoretical reference for the treatment of resistant SBPH.

Inheritance mode and fitness costs of acetamiprid resistance in brown planthopper, Nilaparvata lugens (Stål)

The brown planthopper, Nilaparvata lugens (Stål), is a major rice pest in Asia. Acetamiprid is a widely used neonicotinoid insecticide for N. lugens control. Because of the frequent and excessive applications of chemical insecticides, moderate levels of resistance against acetamiprid have been found in field populations of N. lugens in China. To study the inheritance mode and fitness costs of acetamiprid resistance in N. lugens, an acetamiprid-resistant strain (AC-R) was selected from a susceptible strain (AC-S) in the laboratory. After 28 generations of selection, AC-R showed 26.15-fold resistance compared to AC-S. The LC50 and degree of dominance (D) values of the F1RS and F1SR (progenies of reciprocal crosses) indicated that the acetamiprid resistance in N. lugens was inherited as autosomal and incompletely dominant. Significant differences between the expected and observed mortalities of the F2 individuals suggested that acetamiprid resistance is controlled by multiple genes. The AC-R strain showed a relative fitness of 0.71 with a significantly decreased male adult longevity, fecundity, net reproductive rate (R0), and finite rate of increase (λ), and a prolonged adult preoviposition period (APOP). However, the durations of the 1st, 2nd, and 4th instar nymphs of AC-R were significantly shorter than those of AC-S. The current study provides valuable information for understanding acetamiprid resistance and optimizing insecticide resistance management strategies of N. lugens in the field.

Planthopper-Secreted Salivary Calmodulin Acts as an Effector for Defense Responses in Rice

The brown planthopper (Nilaparvata lugens, BPH) and small brown planthopper (Laodelphax striatellus, SBPH) are major pests of rice (Oryza sativa) in Asia. These piercing-sucking insects secrete saliva into the host during feeding. Nevertheless, it is largely unknown how planthoppers use salivary effectors to enable continuous feeding on rice. Here, we screened their salivary proteomes and selected eight salivary proteins conserved between SBPH and BPH as candidate effectors. Silencing calmodulin (CaM) impeded BPH and SBPH from penetrating the phloem. Hence, their food intake, survival, and fecundity on rice plants were reduced. By contrast, CaM silencing had a small effect on the survival rate of BPH and SBPH raised on artificial diet. The CaM amino acid sequences were the same for both BPH and SBPH. CaM was highly expressed in their salivary glands and secreted into the rice plants during feeding. Bacterially expressed recombinant CaM protein exhibited calcium-binding activity. In planta expression disclosed that CaM was localized to the plant cytoplasms and nuclei and suppressed plant defenses such as hydrogen peroxide (H2O2) accumulation and callose deposition. CaM-silenced BPH and SBPH nymphs elicited relatively high levels of H2O2 and callose accumulation in rice plants. The foregoing results reveal that CaM is an effector as it enables the planthopper to reach the phloem by suppressing callose deposition and H2O2 accumulation in rice.

Efficacy of Indigenous Crude Plant Extracts against Rice Weevil, Sitophilus oryzae L. 1763 (Coleoptera: Curculionidae)

Rice weevil, Sitophilus oryzae L. (Coleoptera: Curculionidae) is a widely distributed and major insect pest of rice that causes considerable losses to both husked and unhusked rice grains. Plant-based pesticides are alternative to synthetic pesticides in managing stored product pests owing to their severe hazardous effects. Thus, locally available plant leaf crude extracts i.e., neem (Azadirachta indica A. Juss 1830), turmeric (Curcuma longa L. 1753), and mint (Mentha longifolia L. Huds. 1762) were investigated at 2 % (w/w) concentration against S. oryzae in unhusked and husked rice. Adult mortality was recorded at 24, 48 hours, and seven days after the application whereas, population build-up was recorded at 1-, 2-, and 3-months intervals. Overall and grain weight loss was also recorded at the end of the experiment. In husked and unhusked rice, the highest mortality percentage was observed in turmeric powder (93.30 %) and neem (80.00 %), respectively. In comparison to plant extracts, relatively higher population growth of S. oryzae was recorded in control husked and unhusked rice. At the end of the 3rd month, the highest and lowest population in husked rice grains was recorded in control (70.67 ± 3.18) and turmeric treatments (18.00 ± 2.65), respectively, whereas control and neem treatments exhibited the highest (83.67 ± 3.28) and lowest (39.67 ± 2.33) populations in unhusked rice. The lowest grain weight loss in husked and unhusked rice was recorded in turmeric (9.33 %) and neem (16.67 %), respectively. Thus, turmeric and neem extracts should be investigated on large scale under commercial warehouses for the management of S. oryzae in husked and unhusked rice.

Role of abiotic factors on the seasonal variation in infestation of the major insect pests of rice (Oryza sativa L.) in Odisha

Role of abiotic factors on the seasonal variation in infestation of the major insect pests of rice (Oryza sativa L.) in Odisha