Ruhul Amin

The fall armyworm (Spodoptera frugiperda) presents a significant threat to corn production in Bangladesh, resulting in considerable yield losses. This study aimed to evaluate the effectiveness of commonly used synthetic insecticides-Winmax 40 WG (Emamectin benzoate), Ripcord 10 EC (Cypermethrin), Marshal 20 EC (Carbosulfan), and Shobicron 425 EC (Profenofos and Cypermethrin)-in managing fall armyworm infestations in sweet corn (variety BU Sweet Corn 1) at the experimental field of Bangabandhu Sheikh Mujibur Rahman Agricultural University in Gazipur, Bangladesh, during the Rabi and Kharif seasons of 2022 and 2023. In the Rabi season, leaf infestations ranged from 0.2 to 5.4%, while cob infestations varied from 5.0 to 20.0%. Conversely, in the Kharif season, leaf infestations spiked between 42.8% and 78.8%, and cob infestations ranged from 40.0 to 90.0%. The application of all insecticides significantly reduced leaf and cob infestations, along with fall armyworm larval populations, compared to the control treatment in both seasons. Specifically, Shobicron 425 EC and Marshal 20 EC demonstrated notable effectiveness in reducing infestation levels. Notably, Shobicron 425 EC treatment resulted in the highest cob length (16.4 cm in Rabi and 11.9 cm in Kharif), cob diameter (4.0 cm and 2.1 cm, respectively), cob weight (196.6 g and 80.3 g), grains per cob (537.2 and 98.0), and overall yield (12.7 t/ha and 6.2 t/ha). Collectively, the study findings indicated that the combination of Profenofos and Cypermethrin demonstrates the highest efficacy in controlling fall armyworm infestations in sweet corn under the tested field conditions. Ann. Bangladesh Agric. 28(1): 31-37

ABUNDANCE, DIVERSITY AND FORAGING BEHAVIOR OF THE FLOWER-VISITING INSECTS OF MANGO IN GAZIPUR, BANGLADESH

Monthly field surveys were conducted across multiple Malta orchards in three upazilas namely Madhupur, Ghatail and Dhanbari under Tangail district from May 2023 to April 2024 to document arthropod species diversity, abundance, and their interactions with the crop. A total of 32 insect species and one mite species found in Malta. Among the species harboured, four insect species and one mite were identified as major pests. Out of the insect species, nine species are shown as minor pest, six species as predators, two species as pollinators and eleven species as casual visitors. From March to May, the abundance of all harboured arthropod species was increased. Scale insects ranked first in the order Hemiptera, with the maximum abundance of 25.1%. The pollinator had the lowest rank with an abundance of 6.06%, while the pest category held the highest rank (42.42%). Casual visitor and predator showed the highest evenness and richness for Malta crops. This study contributes to the understanding of arthropod-crop interactions in the context of Bangladesh’s agricultural landscape.

The study was carried out to investigate the efficacy of three synthetic insecticides namely confidor 70 WG, Actara 25 WG, Liquor 1.8 EC, and neem oil against rose thrips and associated natural enemies. The insecticides confidor 70 WG, actara 25 WG, liquor 1.8 EC and neem oil significantly reduced the population of thrips compared to untreated control. Actara 25 WG and confidor 70 WG were the most effective insecticides against thrips on rose shoot (2.3 ± 0.3 and 3.7 ± 0.3, respectively) as well as flower (6.3 ± 0.9 and 2.7 ± 0.3, respectively). According to the findings, confidor 70 WG, actara 25 WG and liquor 1.8 EC were found harmful to lady bird beetle and spiders and reduced their population. On the other hand, neem oil was less toxic and showed lower population reduction of natural enemies. The reduction percentage of thrips over control showed that actara 25 WG caused the highest reduction on shoot while confidor 70 WG caused the highest reduction on rose flower.

The study was conducted to evaluate the toxicity effect of the insecticides, λ-cyhalothrin, cypermethrin carbosulfan and profenofos Q + cypermethrin on sucking insect pests aphid, jassid, whitefly and thrips of tomato. The leaf dip method following completely randomized design was used. Insecticides showed toxic effects on the sucking pests and varied significantly.λ-Cyhalothrin showed the lowest LC₅₀ and LC₉₅; conversely, profenofos Q + cypermethrin showed the highest LC₅₀ and LC₉₅ for all the tested sucking insects (LC₅₀: 6.9 and 160.3 ppm; LC₉₅: 58.8 and 2340.7 ppm of active ingredients, respectively).

The study examines the impact of temperatures on the development, survival, and morphometrics of cucurbit fruit flies. Developmental times for eggs, larvae, and pupae were influenced by temperature, with longer durations generally observed at lower temperatures. Longevity of male cucurbit fruit flies varied, with the highest duration at 24°C and lowest at 20 and 32°C, while female fruit flies exhibited the highest longevity at 24°C and lowest at 32°C. The offspring production and sex ratio (%) significantly correlated with temperature. Sex ratio(%) highest point at 32°C (68.43 ± 1.09). Optimal conditions for survival were found for the 1st instar at 24°C, while consistent survival rates were noted for the 2nd instar across temperatures. Notably, the 3rd instar and pupae demonstrated temperature-dependent survival rates, with peak viability at 24 and 28°C. The length of cucurbit fruit fly larvae and adults varied significantly across temperatures, with optimal lengths generally observed at 28°C. The width of larvae exhibited temperature-dependent variations, while pupal and adult widths remained consistent. Larval and pupal weights were significantly influenced by temperature, with higher weights observed at intermediate temperatures. Adult weight showed similar trends, with maximum weights recorded at 24 and 28°C for both males and females.

Surveys were undertaken to determine how many different foraging insect species were associated with sweet corn (variety BU Misti Bhutta 1) plants at Gazipur in Bangladesh. In total 33 different insect species were identified belonging to 25 families of 8 orders namely Ephemeroptera, Odonata, Thysanoptera, Hemiptera, Lepidoptera, Coleoptera, Diptera and Hymenoptera. The insects were divided into major pest, minor pest, predator and casual visitors and they occupied 19.9, 48.4, 8.8 and 22.9% abundance respectively. Only one insect species (Spodoptera frugiperda), of major pest, and 10 species of minor pest, 5 species of predator and 17 species of casual visitor were found. Among the harbored insects, Hemiptera occupied the highest abundance (32.2%) and the aphid ranked the top position (25.5%). The pest species was the most dominant group (0.4), while the highest richness (9.9), diversity (1.2) and evenness (1.0) were observed in case of casual visitors. The population of the major pest exhibited a negative link with minor pests but a positive correlation with casual visitors and predators.

The aim of this study was to assess the damage and growth of cucurbit fruit fly B. cucurbitae on bitter gourd using 20, 24, 28 and 32°C temperatures with 80% humidity. At different temperatures, the damage potential of B. cucurbitae reared on bitter gourd was observed highest at 24 and 28°C. Different larval stages of cucurbit fruit fly food consumption was highest at 28°C. The highest feeding index of B. cucurbitae larvae was seen at 20°C and the lowest observed at 28°C. The highest growth index of cucurbit fruit fly reared on bitter gourd was observed at 28°C and the lowest at 32°C. The findings of the research indicate that temperature has a substantial impact on the growth patterns, feeding behavior, and damage potential of B. cucurbitae on bitter gourd. Specifically, the study reports that larval development is most favorable at approximately 28°C.

The effect of host plant physiomorphic characters on the abundance of thrips and jassids were studied on fifteen genotypes which differed significantly in growth duration, morphological characteristics, and biochemical properties of leaf. Thrips started to build up from the first week of May and reached peak during fourth week of June to first week of July (14 to 24 per 5 cm top shoot). The population of jassids remained more or less constant throughout the growing period of okra. Abundance of thrips and jassids varied depending genotypic characteristics of okra. The number of leaves per plant had significant positive effect although leaf area showed negative effect on the abundance of thrips while leaf area of the genotypes showed significant positive relationship with the abundance of jassids. The total chlorophyll content of leaf revealed significant positive correlation with the abundance of jassid. Abundance of the insects from correlation matrices depicted that there was negative correlation between thrips and jassid population in okra genotypes.

Global crop yield and food security are being threatened by phytophagous insects. Innovative methods are required to increase agricultural output while reducing reliance on hazardous synthetic insecticides. Using the revolutionary CRISPR-Cas technology to develop insect-resistant plants appears to be highly efficient at lowering production costs and increasing farm profitability. The genomes of both a model insect, Drosophila melanogaster, and major phytophagous insect genera, viz. Spodoptera, Helicoverpa, Nilaparvata, Locusta, Tribolium, Agrotis, etc., were successfully edited by the CRISPR-Cas toolkits. This new method, however, has the ability to alter an insect’s DNA in order to either induce a gene drive or overcome an insect’s tolerance to certain insecticides. The rapid progress in the methodologies of CRISPR technology and their diverse applications show a high promise in the development of insect-resistant plant varieties or other strategies for the sustainable management of insect pests to ensure food security. This paper reviewed and critically discussed the use of CRISPR-Cas genome-editing technology in long-term insect pest management. The emphasis of this review was on the prospective uses of the CRISPR-Cas system for insect stress management in crop production through the creation of genome-edited crop plants or insects. The potential and the difficulties of using CRISPR-Cas technology to reduce pest stress in crop plants were critically examined and discussed.