The disclosure of insect occurrences correlating with meteorological data is pivotal in devising effective management strategies for rice fields. The study collected data on harmful and beneficial insects, along with meteorological variables, for three consecutive rice-growing seasons in 2021 and 2022. Month-wise insect distribution were delineated, with prominent species such as green leafhopper, brown planthopper, white-backed planthopper, rice whorl maggot, damselfly, parasitic wasps and green mirid bug observed consistently. Notably, most of the harmful insects were predominantly present during March–July and September–October. The spatial distribution, further segmented based on the rice-growing seasons, revealing the Aus season's preeminence in hosting harmful insects followed by Aman and Boro. The prevalence of most of the harmful insects were in tillering stage. Beneficial insects, displayed their dominance during specific months, growth stage, emphasizing their potential role in controlling harmful species and their prevalence were increased by increased of harmful insects. Furthermore, the study elucidated the correlation between climatic factors and insect abundance, emphasizing the role of temperature, rainfall and relative humidity. Temperature metrics and relative humidity manifested significant associations with several insects both harmful and beneficial species differently. While rainfall notably correlated with rice bug, short-horned grasshoppers, yellow stem borer, and non-significant association with other insects. The study underscored mutual dependencies between predator and prey species, emphasizing the ecological balance within the agricultural ecosystem. This comprehensive analysis indicated the need for integrated pest management strategies, considering both harmful and beneficial insect dynamics, to promote sustainable practices for optimizing rice production in changing climatic scenarios.

The role of genetic variation is utmost importance in the selection of a desirable genotype for breeding programs. In the northern region of Bangladesh, the performance of five short duration boro rice varieties (BRRI dhan28, BRRI dhan74, BRRI dhan81, BRRI dhan88, and Bangabandhu dhan100) on yield and yield-contributing traits were evaluated in four locations. Yield attributes tiller hill-1 (TN), panicle hill-1 (PN), filled grain panicle-1 (FG), panicle length (PL), 1000-grain weight (TGW), and harvest index (HI), showed a positive correlation with grain yield (GY). Conversely, spikelet sterility (SSP) and unfilled grains panicle-1 (UFG) showed negative associations with grain yield. Principal component analysis (PCA) revealed that the first three components accounted for 89.60% of variability. The highest positive eigenvalue was observed in DF, DM, BY, HI, PN, SY, TN, PL and GY in PC1, indicating their significant influence on the overall genotype variations. PC2 was primarily driven by plant height (PH) and FG, while PC3 driven by TGW and UFG. The results suggest that grain yield is highly influenced by FG, PH, DM, DF, PN, TN, PL, TGW, SY, BY, and HI. These components highlighted the importance in distinguishing rice genotypes with higher grain yield potential. By considering these traits, BRRI dhan74 have outperformed other varieties, followed by BRRI dhan88 and Bangabandhu dhan100. BRRI dhan74 is most suitable for all four location followed by BRRI dhan88. The traits such as PN, PL, FG, TGW, PH, & HI significantly influence rice yield and should be prioritized in breeding programs aimed at developing high-yielding rice varieties.

Rice weevil (Sitophilus oryzae) is the major seed destroyer in stored grain, causing both quantitative and qualitative losses. Traditional approaches utilizing chemical insecticides including fumigants to address this problem present environmental risks and health concerns. Focusing on the scenario, a study was conducted at laboratory condition of entomology division, Bangladesh Rice Research Institute (BRRI) to assess the efficacy of different botanicals for the management of rice weevils in stored rice. Employing a Complete Randomized Design (CRD) with three replications, the experiment comprised four treatments alongside an untreated control, namely Neem (Azadirachta indica) oil, Mahogany (Swietenia macrophylla) seed kernel powder, Neem (A. indica) leaf powder, Biskatali plants (Polygonum hydropiper) powder and Control (untreated). The findings unveiled that the highest percent of insect mortality was found in neem oil (85%) was followed by biskatali plant powder (75%), neem leaf powder (61.67%), and mahogany seed kernel powder (60%), respectively. The lowest emergence of F1 progeny was recorded in neem oil-treated seeds compared to mahogany seed kernel, Neem leaf powder, biskatali, and untreated control, indicating the efficacy in managing the reproductive capacities of rice weevils. Additionally, neem oil also exhibited the least weight (%) loss of grain compared to other treatments. Regarding seed germination, biskatali plant powder showed the highest germination rate (94%), followed by neem leaf powder (90%), mahogany seed kernel powder (89.67%), neem oil (88%), and control (80.67%), respectively. The research findings indicated that the neem oil and biskatali plant powder have the greatest potential to minimize the current use of synthetic insecticides for rice weevil management in stored rice. SAARC J. Agric., 22(2): 197-207 (2024)

Rice weevils ( Sitophilus oryzae ), a major storage pest, cause both qualitative and quantitative losses of stored grains. Normally, chemical insecticide along with fumigation is practiced for the management, but it creates health hazards. So, this study investigates the effects of temperature and duration of exposure on rice weevils. Completely randomized design with two factors—factor (A) eight treatments: T ₁  = −80°C, T ₂  = −20°C, T ₃  = 4°C, T ₄  = 20°C, T ₅  = 25°C, T ₆  = 35°C, T ₇  = 40°C, and T ₈  = 50°C; factor (B) three durations of exposure—was carried out with three replications at laboratory condition of Entomology Division at Bangladesh Rice Research Institute from October 2023 to November 2024. The mortality percentage varied significantly across temperature and hours exposure time (HET), with 100% mortality observed at extreme temperatures (−80°C, −20°C, and 50°C) at 24, 48, and 72 HET. At moderate temperatures (20°C, 25°C, and 35°C), mortality was negligible to moderate (0%–11.67% at 24 HET and 48 HET), but increasing with prolonged exposure time (48.33% at 72 HET). Although 100% weevil mortality was achieved at 40°C, it required slightly extended durations (48 and 72 HET) for the 100% mortality. The F ₁ adult emergence was highest (124.67) at 25°C, indicating optimal thermal conditions for rice weevil reproduction and development, while extreme temperatures completely inhibited adult emergence. The developmental period was shortest at 25°C and prolonged at 4°C, reflecting the metabolic slowdown at lower temperatures. There were no F ₁ adults emerged at extreme temperatures (−80°C, −20°C, and 50°C), highlighting lethality of these thermal conditions. Weight loss of grains was highest at 20°C, 25°C, and 35°C due to active feeding and breeding, and highest number of F ₁ adults emerged, while the minimal occurred at extreme temperatures. Low (35°C) temperatures were particularly effective with prolonged exposure time for developing temperature‐based management practice. Weevil biology is influence by temperature, with low prolonging development but increasing mortality, moderate optimizing survival, increasing weight loss, and high reducing survival through biological stress.

A lab experiment was conducted during June to October 2021 at Bangladesh Rice Research Institute (BRRI), regional station Rangpur, laboratory to assess the effectiveness of some botanicals i.e., neem (Azadirachta indica), tulsi (Ocimum tenuiflorum) and ginger (Zingiber officinale)) and chemicals (naphthalene) for the management of Anguimous grain moth (Sitotroga cerealella) of rice. The experiment was carried out Complete Randomized Design (CRD) with nine treatments (T₁=Control, T₂=5 whole dried neem leaf, T₃=0.25 ml neem oil, T₄=0.25 g ginger powder, T₅=0.25 g neem leaf powder, T₆= 0.25 g mixture of neem leaf powder and ginger powder, T₇=0.25 g Naphthalene, T₈= 5 whole tulsi leaf and T₉= 0.25 g neem seed powder) and three replications. Study among the nine treatment indicated that T₉ (0.25 g naphthalene) showed better performance in case of insect mortality and no F₁ emergence followed by T₃ (0.35 ml neem oil), T₉ (0.25 g neem seed powder) and T₆ (0.25 g mixture of neem leaf powder and ginger powder). Moderate performance was found T₅ (0.25 g neem leaf powder), T₂ (5 whole dried neem leaf) in case of insect mortality and number of F₁ emergence. But in case of seed germination T₅ (0.25 g neem leaf powder) showed better performance followed by T₇ (0.25 g naphthalene), T₉ (0.25 g neem seed powder), T₆ (0.25 g mixture of neem leaf powder and ginger powder) and T₃ (0.25 ml neem oil). So, naphthalene, neem oil, neem seed powder and neem leaf powder considered as the best treatment among nine treatments for the management of the most destructive Anguimous grain moth.
Bangladesh J. Sci. Ind. Res. 58(3), 155-162, 2023