PG Thesis
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Item Herbicidal management of stem hemiparasite Dendrophthoe spp. in mango orchards(Department of Agronomy, College of Agriculture, Vellanikkara, 2025) Revathi, C; Prameela, PDendrophthoe falcata (Loranthus), a stem hemiparasite of the Loranthaceae family, is a problematic weed in tree crops, including mango. Manual removal of this parasitic weed is the common practice, often involving cutting the infested tree branches. However, it is labour- intensive, often ineffective, and requires repeated intervention due to persistent sub-epidermal haustoria. Even herbicidal sprays for selective control are not available, and use of conventional spraying methods often results in toxicity to the host. Recent technologies such as air-assisted and electrostatic sprayers offer low-volume and target-specific applications with improved canopy penetration and more efficacy. Under this background a study entitled “Herbicidal management of stem hemi-parasite Dendrophthoe spp. in mango orchards” was carried out at the College of Agriculture, Vellanikkara, Thrissur, from October 2024 to September 2025 with the objectives, to assess the efficacy of various herbicides against Dendrophthoe spp. and to evaluate sprayers that can enhance the application efficiency of herbicides for effective management of loranthus. The experiment was carried out on 20-25-year-old mango trees in College Orchard that had been infested with Dendrophthoe falcata for 8-10 years. Treatments were 2,4-D Na salt 80% WP (5 g/L), 2,4-D amine 58% SL (10 mL/L), 2,4-D Na salt (5 g/L) + CuSO₄ (20 g/L), glufosinate ammonium 13.5% SL (10 mL/L), metribuzin 70% WP (5 g/L), ethrel 39% SL (25 mL/L), and metsulfuron methyl 20% WP (0.4 g/L) as targeted foliar sprays. Basal banding (padding) of 2,4-D Na salt (2%) and metribuzin (2%) was also included along with manual removal and unsprayed check. Phytotoxicity symptoms on the parasite and host were observed. In loranthus, changes in biochemical and physiological parameters, nutrient content of leaves, and regrowth up to one year after treatment were assessed. Four types of sprayers, i.e., battery-powered hydraulic, air-assisted, electrostatic, and air compression sprayers, were evaluated by comparing deposition efficiency, weed control efficacy, spray volume requirement, and cost of weed control in order to identify the most efficient technology for targeted herbicide delivery to loranthus clusters. Among the herbicides, though ethrel induced the fastest response through leaf abscission of parasitic weed by two days after spraying (DAS), total control was not obtained and regrowth started by 40 DAS. In metsulfuron methyl sprayed treatments regrowth started by 60 days, while metribuzin sprayed loranthus showed regrowth by 40 days. Foliar application of 2,4-D Na salt and 2,4-D amine provided the most effective and prolonged suppression without any regrowth even up to one year, which indicated complete drying of the parasite without any adverse effect on the host. Manual removal failed to suppress regrowth beyond 3 months. Herbicidal sprays markedly impaired leaf metabolism too. A drastic reduction in total soluble sugars (from 15.26 to 7.63 mg/g), protein (2.28 to 1.79 mg/g), relative leaf water content (50 to 11%), membrane stability (56 to 26%), and chlorophyll (1.64 to 0.92 mg/g) was observed. The NPK content in loranthus leaves also showed a sharp decline. These effects were linked to oxidative stress, disrupted carbohydrate translocation, and accelerated chlorophyll degradation. In contrast, padding with 2,4-D Na salt and metribuzin maintained higher physiological and biochemical values, indicating localized action with minimal systemic translocation and hence ineffectiveness. Significant variation was observed in droplet deposition efficiency among sprayer types, with electrostatic sprayers having the highest deposition (30.5 μL/cm²), followed by air- assisted (12.63 μL/cm²), battery-powered hydraulic (10.0 μL/cm²), and air-compression sprayers (7.23 μL/cm²). Advanced spraying technologies, particularly electrostatic and air- assisted sprayers, reduced spray volume requirement to nearly one-tenth of that used by conventional sprayers. Interestingly, a comparison between droplet deposition rate and weed control efficiency of battery-powered hydraulic and electrostatic sprayers revealed an inverse relationship, wherein higher deposition did not lead to enhanced herbicidal activity. This discrepancy is attributable to the parameters such as spray volume, droplet size, and lethal dose necessary for effective herbicide performance, ensuring adequate wetting, absorption, and translocation to facilitate metabolic action within the host-parasite system. It can be concluded that targeted foliar application of 2,4-D Na salt (80% WP) @5 g/L or 2,4-D amine (58% SL) @10 mL/L, using battery-powered hydraulic sprayer, is an effective method to manage Dendrophthoe infestation in mango orchardsItem Polymer based nano pendimethalin for weed management in rice (Oryza sativa L.)(Department of Agronomy, College of Agriculture, Vellayani, 2025-01-27) Rinsiya, V.The study entitled “Propagation studies in teasel gourd [Momordica subangulata Blume subsp. renigera (G.Don) de Wilde]” was conducted at the Department of Vegetable Science, College of Agriculture, Vellayani during 2023- 2024 to standardize the rooting media and propagation techniques in teasel gourd and to assess the growth and yield under field conditions. The study was conducted as three experiments. The first experiment on “Standardization of propagation using cuttings’’ was undertaken from October to December 2023. The treatments were factorial combinations of three types of cutting (top, middle and basal), four concentrations of IBA (0, 250 ppm, 500 ppm and 750 ppm) and three types of rooting media such as cocopeat, cocopeat + vermicompost (1:1) and cocopeat + vermiculite + perlite (3:1:1) arranged in completely randomized design with three replications. The basal cuttings recorded earliest sprouting (13.76 days), highest percentages of sprouting and survival (61.03 % and 60.08 %), longest shoot length, root length and highest number of roots per cutting. Among IBA concentrations, the earliest sprouting was observed in control (11.48 days), while 250 ppm recorded the highest sprouting percentage (70.07 %), survival percentage (69.07 %), shoot length, number of leaves and primary branches per cutting. The highest number of roots (41.81) and root length (7.34 cm) were observed in IBA 750 ppm. Cocopeat + vermicompost (1:1) media was found to be significantly superior to other media in sprouting, survival and growth parameters. Among the treatment combinations, basal cuttings treated with 250 ppm IBA and planted in cocopeat + vermicompost (1:1) recorded the highest sprouting percentage (85.00 %), survival percentage (83.67 %) and shoot length (48.90 cm) at 45 DAP. Whereas, the highest number of roots was observed in basal cuttings treated with 750 ppm IBA and planted in cocopeat + vermicompost (1:1) 124 (50.67). The second experiment on “Standardization of propagation using tubers’’ was laid out in completely randomized design with six treatments such as two types of tuber (whole tuber, cut tuber) and three types of potting media (soil + cocopeat + FYM (1:1:1), cocopeat + vermicompost (1:1) and sand) replicated four times. Cut tubers exhibited earliest sprouting, (15.36 days) maximum sprouting and survival percentages (75.83 % and 74.83 %), highest shoot length (140.50 cm), number of leaves and root length per tuber. Whereas, the highest number of shoots (2.97) and roots (42.22) were recorded in whole tubers. Among the potting media, soil +cocopeat + FYM (1:1:1) showed the best results in sprouting, survival and in other growth parameters, which was on par with cocopeat + vermicompost (1:1) medium. Among the treatment combinations, cut tubers planted in soil + cocopeat + FYM recorded the highest survival percentage (86.50 %), shoot length (158.49 cm), number of leaves (27.83) and root length (31.61 cm) at 45 DAP. The three best treatments from experiments I and II were selected along with seedlings for the third experiment ‘Evaluation of propagule in the field’. The field experiment was laid out in RBD with seven treatments in three replications. The treatments were, T1 - basal cuttings treated with 250 ppm IBA and planted in cocopeat + vermicompost, T2 - middle cuttings treated with 250 ppm IBA and planted in cocopeat + vermicompost, T3 - basal cuttings without IBA treatment and planted in cocopeat + vermicompost, T4 - cut tuber planted in soil + cocopeat + FYM, T5 – cut tuber planted in cocopeat + vermicompost, T6 - whole tuber planted in soil + cocopeat + FYM and T7- seedlings. The longest vine (10.13 m), number of days taken for first flowering (32.78 days), number of days to first harvest (40.89 days) and longest crop 125 duration (236.22 days) were recorded in T4 (cut tuber planted in soil + cocopeat + FYM). The highest number of fruits per plant (132.33) and yield per plant (8.47 kg) was recorded in T5 (cut tuber planted in cocopeat + vermicompost). Seedlings (T7) recorded the highest number of tubers per plant (11.22). Whereas, tuber yield per plant was the highest in T6 (whole tuber planted in soil + cocopeat + FYM) (790.10 g). The study revealed that basal cutting treated with 250 ppm IBA and planted in cocopeat + vermicompost (1:1) media as well as cut tubers in soil + cocopeat + FYM were found to be the best for production of quality planting material in teasel gourd. The plants propagated through tubers were superior in growth and yield attributes under field condition.