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Birsa Agricultural University, Ranchi

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Subject: Agricultural Meteorology × Author: Marandi, Atul × End date: 2023 × Start date: 2020 × Type: Thesis × Thesis Type: M.Sc ×
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    ThesisItemOpen Access
    CROP WEATHER, INSECT-DISEASE RELATIONSHIP IN OKRA
    (Birsa Agricultural University, Ranchi, 2022) Marandi, Atul; Kumai, Pragyan
    The field experiment was conducted during 2021 at Agrotechnology Park, Birsa Agricultural University, Ranchi to investigate the “Crop weather, insect-disease relationship in okra” of seven different dates of sowing. The experiment was laid out in a randomized block design with four replications along with seven treatments. Thermal and radiation indices accumulated (GDD, HTU, PTU, HUE) at different Phenophases were highest in 15th March sown crop (D1) as compared to other sowing date, this is due to more days taken by D1 to attain the different developmental Phenophases and higher temperature. Okra sown on March 15 (D1) had produced significantly higher number of branches per plant, number of fruits /plant and yield of okra (73.8 q ha-1) followed by D3 sown crop (62.4 q ha-1). All the treatments were significantly different among themself. The delay in sowing significantly reduced the green fruit yield of okra upto 23% which could be due to the infestation of pests and diseases of okra. Yield of okra was significantly and positively correlated with Tmax (r=0.695*) and BSS (r=0.882*) and negatively associated with Tmin(r=-0.752**), RHI(r=-0.331*), RHII (r=-0.762**) and Rainfall (r=-0.754*). The significant negative correlation was obtained with Tmax. (r=-0.289**) while rainfall (r=0.587**) was found significantly positively correlated. The multiple regression model developed with weather parameters explained 56% variability in aphid population. The jassid population were significantly negatively correlated with Tmax. (r=-0.441**), RHI (r=-0.279*), RHII (r=-0.271*) and BSS (r=-0.295*) while significantly positive associated with rainfall (r = 0.375**). The multiple regression model developed with weather parameters explained 60% variability in jassid population. The whitefly population was significantly negatively correlated with Tmax (r=-0.377**) and BSS (r=-0.452**). Wind speed (r=0.411**) and rainfall (r=0.385**) which was found significantly positively influences the population of whitefly. The multiple regression model developed with weather parameters had slightly better predictability (R2 = 0.53). The fruit and shoot borer population were found significantly negatively correlated with Tmax. (r=-0.401**), RHI (r=-0.316*) and BSS (r=-0.348**) but significantly positively correlated with rainfall (r=0.606**). The multiple regression equation revealed that the various abiotic factors were found to be most influencing factors which contributed R2= 0.59 (59%) variation in fruit and shoot borer population. The OYVMV disease infestation was significantly negatively correlated with maximum temperature, morning relative humidity, bright sunshine hours and significantly positively correlated with wind speed and rainfall. Multiple regression equation for prediction of OYVMV disease using maximum, minimum temperatures, morning and evening relative humidity and rainfall together explained 43 percent variation in disease attack in okra. Cercospora disease was highly significantly negatively correlated with maximum temperature (r=-0.346**), morning relative humidity (r=-0.293*), bright sunshine hours (r=-0.359**) and highly significantly positively correlated with wind speed (r=0.413**) and rainfall (r=0.645**). The multiple regression equation revealed that the various abiotic factors were found to be most influencing factors which contributed R2= 0.54 (54%) variation in cercospora disease in okra. Weather parameter were found to have significant influence not only on growth and yield of okra but also initiation and development of pests and disease of okra. The agrometeorological indices (GDD, HTU, PTU) required for maturity of crop was highest in okra sown on D1(15th March) and lowest for D7(15th June). First date of sowing (15thMarch) registered significantly highest yield with minimum infestation of diseases and pests. Maximum temperature was significantly and negatively associated with population of all insects and diseases under study where as it was significantly positive corelated with rainfall in okra under Ranchi region. Increase in bright sunshine hours would decrease the infestation of jassid, whitefly, fruit and shoot borer, OYVMV and cercospora disease in okra. Wind speed during crop period would increase the dissemination of OYVMV and cercospora diseases and whitefly population in okra. Morning relative humidity negatively influenced the population of jassid, fruit and shoot borer, OYVMV and cercospora disease in okra while evening humidity was also associated negatively with jassid population. It is recommended that early sowing of okra would be advisable for farmers of Jharkhand to escape from pests and disease infestation. Early forewarning of disease and insect infestation would be possible on the basis of above investigation and risk can be minimized by spraying the pesticides in advance.