Browsing by Author "Gowri Priya"

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Bioefficacy of entomopathogenic fungi against cassava mealybug, phenacoccus manihotti matile-ferrero (Hemiptera: Pseudococcidae)
(Department of Agricultural Entomology, College of Agriculture,Vellanikkara, 2024-02-21) Fasna, Sherin, K.; Smitha Ravi; Gowri Priya
Cassava mealybug (CMB), Phenacoccus manihoti Matile-Ferrero (Hemiptera: Pseudococcidae) is a major insect pest of cassava. It causes severe damage by stunting the growth points of cassava plants, sometimes totally defoliating the plants. Level of infestation and yield loss by cassava mealybug varied from 30 to100 and 30 to 90 per cent respectively. In India, the occurrence of this pest was first noticed on cassava in Thrissur, Kerala during April 2020. Control of mealybugs commonly relies on the use of insecticides. But, it is difficult to control mealybugs using insecticides, due to their cryptic life cycle, presence of waxy coating, and formation of dense colonies. Management of insect pests using entomopathogens has received considerable importance in recent times. As part of AICRP programme of 2020-22, AICRP on BCCP, Thrissur centre conducted survey in cassava growing fields of Thrissur and Palakkad district to assess the species composition of mealybugs, damage intensity and associated natural enemies. During the survey, mycosed cadavers were collected and seven isolates of entomopathogenic fungi were obtained. Out of seven, five entomopathogenic fungal isolates were selected, characterized and evaluated under the present study entitled “Bioefficacy of entomopathogenic fungi against cassava mealybug, Phenacoccus manihoti Matile-Ferrero (Hemiptera: Pseudococcidae)”. The identity of five isolates was confirmed through morphological, cultural and molecular characterization. The fungal isolates were identified as two isolates of Simplicillium aogashimaense (EPF 2 and EPF 4), two isolates of Purpureocillium lilacinum (EPF 3 and EPF 7) and one isolate of Lecanicillium psallioate (EPF 5). Pathogenicity of these fungal isolates was tested against second instar nymphs of cassava mealybug, P. manihoti in the laboratory. A preliminary screening bioassay was carried out initially, and the superior isolates were subjected to dose-response and exposure-time response bioassay. In the preliminary screening bioassay, P. lilacinum isolates (EPF 7 and EPF 3) recorded more than 90.0 per cent mortality. S. aogashimaense (EPF 4) and L. psalliotae (EPF 5) registered mean mortality of 82.5 and 75.0 per cent respectively. S. aogashimaense (EPF 2) recorded the lowest mortality of 70.0 per cent, which was significantly lower than all other isolates. The best four isolates in the pre-screening were subjected to dose-response and exposure time- response bioassay. Spore suspensions of five different concentrations ranging from109 to 105 spores ml-1 were tested against mealybug. Ten days after treatment, two isolates of P. lilacinum (EPF 7 and EPF 3) recorded more than 80.0 per cent reduction in population of mealybug at the concentration of 109 spores ml-1 . The same isolates showed low LC50 and LT50 values. Efficacy of these two superior isolates of P. lilacinum (EPF 7 and EPF 3) at concentration of 1×108 spores ml-1 was evaluated in a pot culture experiment. The isolates were compared with a standard biocontrol check, NBAIR isolate of Lecanicillium lecanii @ 1×108 spores ml-1 , a botanical insecticide (neem oil emulsion @ 2%) and a chemical insecticide, dimethoate 30 EC @ 1.5 ml L-1 . Maximum reduction in the mealybug population was observed in dimethoate treated plants (99.86%). Even though, the neem oil emulsion (2%) showed significant effect on mealybugs, certain signs of phytotoxicity were observed in treated plants. Among three fungal isolates, significantly higher reduction in population was observed in P. lilacinum, EPF 7 (78.55%) followed by P. lilacinum, EPF 3 (74.92%), and both being on par with each other. In conclusion, the present study revealed that biological control of cassava mealybug, P. manihoti using two promising isolates of P. lilacinum could be a viable component in the integrated pest management. Two rounds of foliar application of any of the two isolates of P. lilacinum (EPF 3 and EPF 7), at 15 days interval at the dosage of 1×108 spores ml-1 was found effective against cassava mealybug, P. manihoti.
Development of protocol for quality control of commercial organic manures and their evaluation
(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 2008) Gowri Priya; Harikrishnan Nair, K
Soil quality assessment and evaluation of rejuvenation strategies for coastal sandy soils of thiruvanathapuram district (AEU 1) through organics
(Department of soil science and agricultural chemistry, college of agriculture,Vellayani, 2023-08-01) Athulya, B M.; Gowri Priya
A study entitled “Soil quality assessment and rejuvenation of coastal sandy soils of Thiruvananthapuram district (AEU 1) through organics” was carried out with an objective in assessment of soil quality of coastal sandy soils in Thiruvananthapuram district (AEU 1) and development of organics based rejuvenation methods. The study was carried out in two phases. As phase 1, characterization of southern coastal soils of AEU 1 in Thiruvananthapuram district was done. Based on the results of phase I, an area with low fertility was selected for phase 2 of the study. Different organic amendments were applied to study the effect on soil properties and crop growth in phase 2. Fifty geo-referenced surface soil samples, along with core samples were collected from coastal areas in AEU 1 of Thiruvananthapuram district and characterized for various physical (texture, bulk density, particle density, water holding capacity and soil aggregate stability), chemical (pH, EC, cation exchange capacity, exchangeable acidity, organic carbon, available macronutrients, available micronutrients such as Fe, Mn, Zn, Cu, B, Cl, Na and heavy metals (Pb and Cd)) and biological attributes (dehydrogenase activity and microbial biomass carbon). Principal component analysis was used to set up the minimum data set of indicators to compute the soil quality index. Six principal components were extracted from which ten indicators that highly influenced the soil quality were identified, viz. clay per cent, water holding capacity, bulk density, soil pH, organic carbon, available K, available S, available Zn, available Mn and available B. Scores and weights were assigned to each indicator, and were aggregated to compute the soil quality index. The relative soil quality index of the soils were also found. GIS techniques were used to prepare thematic maps of major soil attributes and relative soil quality indices of the coastal sandy soils of AEU 1. Correlations were worked out among the various analysed parameters. The analytical results for soil physical properties showed that the predominant soil textual class observed in the present study area was sand and loamy sand. Bulk 192 density was in the range of 1.37 - 1.86 Mg m- ³, particle density 2.22 - 2.89 Mg m- ³, with 22.7 – 56 per cent water holding capacity and 33.6-59.4 per cent soil aggregate stability. The soil pH ranged between 5.11 - 7.19, and 0.03 - 0.23 dS m-1 for electrical conductivity. Organic carbon was found in the range of 0.07 - 1.01 per cent, nitrogen 100 - 308 kg ha-1 , phosphorus 7.05 - 59.94 kg ha-1 and potassium 100 - 361 kg ha-1 . Secondary nutrients ranged as: calcium 80 - 360 mg kg-1 , magnesium 47 - 152 mg kg-1 and sulphur 4.5 - 20.5 mg kg-1 . The available micro nutrients ranged between: 6.63 - 81.57 mg kg-1 for iron, 2.53 - 36.01 mg kg-1 for manganese, 2.21 - 16.64 mg kg-1 for zinc, 0.11 - 6.07 mg kg-1 for copper and 0.11- 0.82 mg kg-1 for boron. Heavy metals such as Cd and Pb were below detectable limit. Soil biological activity in these soils were poor with dehydrogenase activity in the range of 5.57 – 20.29 µg TPF hydrolysed g-1 soil 24 hrs-1 and microbial biomass carbon of 9.18 - 29.96 µg g1 soil. So, generally the fertility status of this coastal sandy soils was found to be low. Majority of the soils belonged to medium soil quality (60 %), followed by good (36 %) and poor (4 %) quality. The soils of Kadakkavoor recorded the highest soil quality index and that of Anchuthengu, recorded the lowest. Based on the results of phase I, a pot culture experiment was done at Kochuveli, Industrial area, Thiruvananthapuram with Amaranthus (variety: Arun) as test crop. The experiment was completely randomized design (CRD) with 12 treatments and 3 replications. In the pot culture experiment, treatments included were; T1: Control, T2: Organic POP, T3 : Vermicompost, T4: Liming + Vermicompost, T5 : Coir pith compost, T6: Liming + Coir pith compost, T7: City compost, T8: Liming + City compost, T9: Suchitha, T10: Liming + Suchitha, T11: FYM 12.5 t ha-1 + Biochar 12.5 t ha-1 , T12: Liming + FYM 12.5 t ha-1 + Biochar 12.5 t ha-1 . In T2 (organic POP), FYM @ 25t ha-1 as basal dose and top dressing with fresh cow dung slurry @ 1kg per 10 litres (50 kg ha-1 ) was done. Along with that, 272.7 kg rock phosphate and 122.5 kg potassium sulphate ha-1 were applied. From T3 to T10, as per organic POP manure recommendation, basal dose of FYM was substituted with organic amendments @ 25 t ha-1 with or without lime application. 193 Soil management using organic manures had considerable impact on growth and yield characteristics of plant. Highest plant height was observed in T8, which was on par with T4 and T10. Highest dry matter and yield were recorded in T10 which was followed by T4. Effect of organic manures on quality parameters showed that highest β carotene and nitrate content were recorded in T10. Highest vitamin C content was recorded in T10 which was on par with T3 and T4. Being an antinutritional factor, T1 recorded the highest value of oxalate content and the lowest was seen in T10. Regarding the nutrient uptake in plants, T10 recorded the highest uptake of N, K, Ca and Mg, while T4 recorded the highest in P and S uptake. Analyses of post-harvest soil for nutrient parameters showed that the highest value of organic carbon was recorded in T10, which was on par with T8 and T9. The highest value for available nitrogen was recorded for T10 while the highest value for available phosphorous was recorded in T4. The potassium content was found to be the highest in T10. Also T10 showed the highest value in available secondary nutrients. Micronutrients analyses showed that highest content of available Fe was present in T3, while highest of available Cu, Zn and B were recorded in T10. T9 showed the highest value in available Mn. T1 showed highest available Na and Cl content. Analyses of soil biological properties due to the effect of organic manure addition showed that the highest value of dehydrogenase activity was found in T8, which was statistically on par with T7 and T10. Also, the highest value in microbial biomass carbon was found in T8, which was on par with T7, T9, and T10. The highest B: C ratio was recorded by T10. From the study, it is concluded that soil test based lime application and basal application of Suchitha @ 25 t ha-1 , top dressing with fresh cow dung slurry @ 1kg per 10 litres, along with 272.7 kg rock phosphate and 122.5 kg potassium sulphate ha-1 was observed to be the best treatment to improve the soil quality, yield and quality parameters of amaranthus in coastal sandy soils of AEU 1 in Thiruvananthapuram district.
Standardization of production technique of liquid organic manure (Panchagavya) for soil health and crop productivity
(Department of Soil Science and Agricultural Chemistry, College of Agriculture,Vellayani, 2025) Raseena Mol.; Gowri Priya
The study, “Standardization of production technique of liquid organic manure (Panchagavya) for soil health and crop productivity,” aimed at standardizing Panchagavya production to reduce local variability, evaluating its chemical properties, and assessing its impact on soil health and crop productivity using bhindi (var. Anjitha) as a test crop. The research was divided into two parts: standardizing the Panchagavya production method and evaluating its influence on soil health and crop productivity. To determine the optimal composition, the study used eight ingredients in 81 combinations, testing four key components (cow urine, ghee, milk and curd) in varying amounts, while keeping the levels of cow dung, coconut water, jaggery and banana constant. The design followed a Completely Randomized Design (CRD) with two replications. The Panchagavya preparations were analyzed for physical and chemical properties, and a germination study evaluated their phytostimulant potential. Based on this, the 20 most effective treatments were selected, and their biochemical constituents were analyzed. Principal Component Analysis (PCA) was then conducted to select the top ten treatments, followed by a microbial count analysis. The Panchagavya preparations from all treatments had an acidic pH, ranging from 5.11 to 5.76. Electrical conductivity (EC) ranged from 6.00 dS m-1 to 7.15 dS m-1, and nutrient content varied significantly across treatments, with T81 generally having the highest values. The nitrogen levels varied from 1.12 per cent to 2.66 per cent, phosphorus from 0.12 per cent to 0.39 per cent, and potassium from 0.35 per cent to 0.66 per cent. Calcium content ranged from 186.30 mg L-1 to 256.60 mg L-1, while micronutrients like Fe, Mn, Zn and Cu were also measured, with T81 often exhibiting the highest concentrations. All Panchagavya preparations improved bhindi seed germination compared to the control, though differences between treatments were not statistically significant. Root length ranged from 2.40 cm in T1 to 4.98 cm in T81 which showing a 114.66 per cent increase over the control. Based on the germination study, the top 20 treatments were selected. Indole acetic acid (IAA) and Gibberellic acid (GA) concentrations were highest 187 in T81 and lowest in T54 among these treatments. Ten treatments were further screened through PCA: T59, T60, T61, T62, T67, T68, T69, T70, T76 and T77. Among these, T70 showed the highest bacterial, fungal, and actinomycetes counts, indicating a robust microbial presence. To evaluate field-level effects, a pot experiment was conducted using the selected treatments (as T1–T10), a KAU POP recommendation (Crops, 2016) (T11) and a control without the application of any fertilizers of manures (T12). Post-harvest soil analysis indicated that Panchagavya-treated soils had lower bulk density and higher organic carbon content compared to the control. Treatments T8, T4, T7 and T10 showed the highest nutrient availability, including N, P and K and high values for microbial counts and soil enzyme activities like urease and dehydrogenase, enhancing soil health. Plant growth parameters in the pot experiment showed that T8 produced the tallest plants (137 cm), with the highest dry matter (73.93 g/plant) and chlorophyll content. Yield parameters, including fruit length, girth, number of fruits and average fruit weight, were also highest in T8, resulting in the highest total fruit yield per plant (365.04 g). Treatments T4, T7 and T10 performed in a similar manner with high protein content, low crude fibre, and high ascorbic acid in fruits. Nutrient analysis of bhindi shoots and fruits revealed that T8-treated plants had the highest concentrations of essential macro- and micronutrients (N, P, K, Ca, Mg, S, Fe, Mn, Zn and Cu), indicating enhanced nutrient uptake with no significant difference between treatments T4, T7 and T10. The highest Benefit-Cost (B:C) ratio was recorded in T8 and T4 (1.69). The results of the pot culture experiment indicated that treatment T8 (U12G1M3C2.5) exhibited superior quality effects on bhindi productivity, with no significant difference between the treatments T4, T7 and T10. Based on the B:C ratio analysis, treatment T4 was found to have a lower cost compared to treatment T8, making it a more economically viable option for farmers, which comprises of Panchagavya prepared with 2 L of cow urine, 0.75 kg of ghee, 4 L of milk, 2 L of curd, 7 kg of cow dung, 3 L of tender coconut water, 3 kg of jaggery, and 0.5 kg of ripe poovan banana.