Browsing by Author "Reji Rani, O P"

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Bioecology and life-tables of the pea aphid (Aphis Craccivora Koch. ) and its natural enemies
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 1995) Reji Rani, O P; Remamony, K S
The seasonal distribution of pea aphid Aphis craccivora and its predators on twigs and pods of cowpea and a perennial alternate host of the insect, glyricidia were assessed during 1993 – 94 at the College of Agriculture, Vellayani, Kerala. On cowpea peak population of the pest during the first season, on twig and pods were noted in January / February while on glyricidia two peaks were noted in the season first from December and early February and the next from February to end to early March. In the second season also one peak period each were seen on twigs and pods of cowpea and on glyricidia, but the three did not coincide in the periods of occurrence. In glyricidia a fourth peak was observed in August / September 1994. Studies thus revealed vital indifference in the trend of population build up on cowpea and glyricidia and even on the twigs and pods of the same plant. The growth stages of the crops and their nutritive status are suggested as the major factor influencing the population build up of A. craccivora than any other factor in the ecosystem. Survey of natural enemies in the region revealed the occurrence of six predators and one insect pathogen. Among them C. sexmaculata and x. scutellare were found to be the important ones. A pest dependent increase in the population of predators were observed but the trends of the population build up of the pest and the natural enemies did not show any effective role of the predators in suppressing the pest population under field condition. The detailed biology of A. oraccivora and the two predators were studied in the laboratory conditions. The duration and percentage survival of each larval instar, adult longevity and fecundity were studied and the data indicated that short duration and higher fecundity od A. craccivora when compared to predators account for the successful establishment of the pest in field even with higher levels of predator population. The parameters of biology in laboratory were found more favourable for the population of X. scutellare than for C. sexmaculata. But in field latter was more successful. Feeding potential of C. sexmaculata ( larvae and adult) was much higher than that X. scutellare (larvae) only. Hence C. sexmaculata was found to be a better bicontrol agent for the control of A. craccivora. The exhaustive information gathered will be useful in cinstructing models for integrated pest control programmes of A. craccivora. Age specific life-tables were consctucted for A. craccivora for assessing the intrinsic rate of increase and germination time of pest and these were found suitable for fast population build up. Life tables were prepared during, December 1993 and January 1994 and the ‘Generation survival’ and ‘Trend Index’ were found increasing in January. The lower mortality percentage of the late instar nymphs were found as the reason for the variations. But the mortality factors could not be precisely determined in the investigations. Series of such life tables developed for different seasons, hosts and different ecosystems may be necessary for constructing suitable models for integrated pest management practices.
Bioefficiency of capsule formulations of Beauveria and Metarhizium managing banana weevils
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2020) Devi Balakrishnan; Reji Rani, O P
Compactibility and synergism of the entomopathogentic fungus lecanicillium saksenae (Kushwaha ) Kurihara and Sukarno with other crop protectants
(Department of Agricultural Entomology, College of Agriculture, Vellayani t, 2019) Keerthana, K; Reji Rani, O P
Efficacy and biosafety evaluation of the entomopathogenic fungus Lecanicilliumsaksenae (Kushwaha) Kurihara and Sukarno
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2025-07-17) Karthik, R.S; Reji Rani, O P
The investigation entitled “Efficacy and biosafety evaluation of the entomopathogenic fungus Lecanicilliumsaksenae (Kushwaha) Kurihara and Sukarno” was carried out during 2019 to 2024 at the Department of Entomology, College of Agriculture, Vellayani. The objectives of the study were to evaluate the efficacy of bioformulations of L. saksenae in managing the cowpea pod bug Riptortuspedestris, and to evaluate its biosafety to non-target organisms, including productive insects, pollinators, natural enemies, and mammals. A field experiment conducted in cowpea variety Jyothika, with five treatments viz. (T1) chitin enriched oil formulation of L. saksenae, 108 spores mL-1 @ 10 mL L-1 (T2) talc based formulation of L. saksenae, 108 spores mL -1 @ 20 g L-1 , (T3) L. saksenae spore suspension, 108 spores mL -1 @ 20 mL L-1, (T4) talc formulation of L. lecanii, 108 spores mL-1 @ 20 g L-1 (T5) dimethoate 30 % EC @ 1.5mL L-1. Of these, foliar application of chitin enriched oil formulation of L. saksenae was the superior treatment as it recorded a significantly lower population of the pod bug, R. pedestris. The reduction in population was 34 per cent after the first application and by 21.33 per cent after the second spray, which was equally effective as the insecticide dimethoate 30% EC sprayed at 1.5mL L-1. Population of predators such as the coccinellid beetle, Coccinellatransversalis and spiders Lycosapseudoannulata and Oxyopes sp. did not vary significantly, indicating its safety to natural enemies associated with cowpea ecosystem. Experiment to assess the safety of L. saksenae to non-target organisms was carried out using a concentration that is tenfold higher (109 spores mL-1) than the infective dose to insects. Safety to productive insects was examined using Indian bee, Apisceranaindica and the stingless bee Tetragonulairidipennis. L. saksenae conidial suspension exposed by dry film method did not cause any symptoms of mycosis such as irritability, sluggishness or disoriented movements in adult bees throughout the observation period. Topical application of the conidial suspension did not exhibit any significant difference in the colony strength, brood area (139 to 272.5 cm2) and storage area (31 to 136 cm2) of honey and pollen. There were no behavioural abnormalities nor symptoms of mycosis during the experimental period of ten weeks and the brood development was comparable with that of untreated colonies. The safety test carried out in adult T. iridipennis using the same method, revealed that the fungus was not pathogenic to it, as there were no symptoms of mycosis such as irritability, sluggishness or disoriented movements, till the fourth day post treatment. The colonies treated with conidial suspension did not exhibit symptoms of mycosis or mortality. The coccinellid predator, C. transversalis treated using dry film revealed no symptoms indicative of fungal infection. The cumulative mortality of treated grubs observed for a period of five weeks did not differ significantly with that of untreated (90 and 100 per cent respectively). They pupated normally and the percentage adult emergence was comparable with that of the untreated group (40 per cent each). The larval syrphid predator Dideopsisaegrota tested for its susceptibility to L. saksenae completed its life cycle normally with no symptoms of fungal infection. The mortality recorded four days after treatment was 40 per cent in the treated as well as control group. The larval parasitoidBraconbrevicornis, exposed to the conidial suspension by dry film method did not develop any disease. The cumulative mean mortality of adults did not differ significantly till 12 days of treatment between the treated and untreated (98-100 per cent). Similarly, there was no symptoms of infection in the larval parasitoidGoniozusnephantidis till seven weeks of exposure. The mortality recorded was on par (74 -76 per cent) in both the groups after six weeks of treatment. The egg parasitoidTrichogrammachilonis, emerged normally after treatment and the rate of adult emergence was 11.31 to 94.30 in treated and 14.76 to 98.46 in control, which did not vary significantly from each other. The pollinators Halictus sp. and D. aegrota. topically treated with L. saksenae showed no signs of mycosis, abnormal behavior, or mortality, further validating the safety of L. saksenae to beneficial insects. To evaluate biosafety of L. saksenae in mammals, the experiment was carried out in Department of Veterinary Pathology, College of Veterinary and Animal Sciences, Mannuthy. The acute toxicity studies were conducted on eight weeks old healthy Wistar albino rats (Rattusnorvegicus) weighing 150 – 200 g. The experiment was laid in CRD with three routes of administration viz. oral, dermal, intranasal administration of L. saksenae (6 × 109 spores mL⁻¹) and a control group with six animals per route of adminstraion. Treated animals were observed for clinical, haematological parameters and histopathological changes. The results revealed that there was no variation in body temperature, food and water intake and weight gain during the experimental period. Haematological parameters such as RBC, WBC, haemoglobin, packed cell volume (PCV), mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), granulocyte count, agranulocyte count, and platelet count were within the normal range in the treated and untreated animals. Serum biochemical analysis of orally treated animals performed to estimate liver function parameters, including alkaline phosphatase (ALP), serum glutamic oxaloacetic transaminase (SGOT), serum glutamic pyruvic transaminase (SGPT), total protein, albumin, and globulin, as well as the renal function parameters, including urea, creatinine, and uric acid. There were no abnormalities in the test results obtained. Euthanized animals exhibited normal gross morphology and histopathological observations did not reveal any significant pathological lesions in the vital organs including brain, liver, kidneys, lungs, spleen, skin and intestines, confirming the non pathogenic nature of L. saksenae to mammals. In conclusion, the chitin enriched oil formulation of L. saksenae offers a viable alternative to chemical pesticides for managing the major sucking pest of cowpea, the pod bug, R. pedestris, without compromising the safety of natural enemies. The fungus also proved safe to productive insects, pollinators and mammals, strongly supporting its candidature in sustainable and ecofriendly pest management programmes.
Efficacy of chitin enriched formulations of lecanicillium spp against sucking pests of rice Oryza sativa L.
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2017) Hari Sankar, S S; Reji Rani, O P
Endophytic association of entomopathogenic fungi with rice and cowpea
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2019) Divyashree, C; Reji Rani, O P
The study entitled ‘Endophytic association of entomopathogenic fungi with rice and cowpea’ was carried out in the Department of Agricultural Entomology, College of Agriculture, Vellayani, Thiruvananthapuram, during the year 2017-19, with the objective to examine the endophytic association of entomopathogenic fungi in rice and cowpea. The entomopathogenic fungi, evaluated were Beauveria bassiana, Metarhizium anisopliae, Lecanicillium lecanii and Lecanicillium saksenae. They were tested through seven inoculation methods viz., seed coating, seed soaking, radicle dressing, root dipping, soil drenching, foliar spraying and bloom spraying by inoculating the conidial suspension at their effective doses. Among the four entomopathogenic fungi inoculated, B. bassiana, M. anisopliae and L. saksenae were found to colonise rice plants. B. bassiana was found to colonise in stem and roots, while M. anisopliae preferred stem. Both B. bassiana and M. anisopliae colonized effectively by seed soaking method. L. saksenae colonised in the stem and roots in seed soaking, in the roots in soil drenching and in the leaves in foliar spraying method. In plants, B. bassiana and M. anisopliae persisted up to 15th day after inoculation (DAI), while L. saksenae persisted till 45th DAI. In soil, L. saksenae persisted in soil up to 45th day, while other fungi could not be retrieved from soil. L. lecanii could not be retrieved from any of the plant parts or soil up to 45th DAI. Thirteen natural endophytes were isolated from rice, which included growth promoters with nitrogen fixing properties, gibberellic acid production properties, saprophytes and plant pathogens. They were identified with the help of colony and conidial characters. Those fungal endophytes whose identity could not be confirmed were characterised at molecular level through ITS sequencing, and bacterial endophytes through 16S sequencing. The most dominant endophyte in rice was the fungus, Neocomospora rubicola, a known plant pathogen followed by the nitrogen fixing bacterium Burkholderia cepacia. Colonisation of fungal bacterial association Sarocladium oryzae + Kosakonia sacchari was also dominant in the stem. S. oryzae is a known plant pathogen while K. Sacchari is a nitrogen fixing bacterium. The other endophytes with less frequency of occurrence were Pestalotiopsis microspora, Cladosporium sp., Microdochium fisheri, Fusarium solani, Aspergillus and Penicillium. Experiments in cowpea revealed that all the four fungi could successfully colonize different plant parts. Foliar spraying was the best method in cowpea to get endophytic association of all the four fungi, while M. anisopliae could also be retrieved through seed soaking and root dipping methods. B. bassiana, M. anisopliae and L. saksenae were found to colonise leaves, stem and roots, while L. lecanii colonised only on leaves. In cowpea plants, M. anisopliae and L. saksenae were found to be more persistent (up to 45th DAI), while B. bassiana and L. lecanii persisted only up to 30 DAI. Soil samples revealed the presence of B. bassiana, M. anisopliae and L. saksenae up to 15th, 30th and 45th DAI respectively. L. lecanii was not found to colonise soil. Grain samples in rice and bloom samples in cowpea did not reveal the presence of any endophytes. In cowpea, several natural endophytes were found to be stumped upon in different parts, which included four fungi and two bacteria. Apart from this a fungal bacterial association, Fusarium + Ebc 3 (unidentified bacterium) was found to be a dominant endophyte. The bacterium Rhizobium mayense isolated from all plant parts was the most dominant endophyte. The other endophytes isolated were the fungi, Cladosporium sp., Clonostachys rosea, Chaetomium globosum and Cerrena sp. and the bacterium Enterobacter cloacae. Rice plants inoculated by seed soaking, with the conidial suspensions of B. bassiana and M. anisopliae @ 108 spores ml-1 and L. saksenae @ 108 spores mL-1 reflected 28.79, 27.17 and 29.99 per cent increase height, 47.71, 44.75 and 47.92 per cent increase in biomass and 37.73, 36.97 and 39.89 per cent increase in grain yield, the highest values being those of L. saksenae and lowest being those of M. anisopliae. Incidence of rice bug assessed in terms of percentage of chaffy grains per panicle was significantly less in L. saksenae (14.21), while in B. bassiana it was 20.48 and in M. anisopliae, 21.61. There was no disease incidence in treated as well as control plants. It is concluded that B. bassiana, M. anisopliae and L. saksenae has endophytic association with rice and cowpea and L. saksenae is a strong endophyte.
Field efficacy of biocapsules of entomopathogenic fungi for the management of vegetable pests
(Department of Agricultural Entomology, College of Agriculture,Vellayani, 2022) Parvathy Maloth; Reji Rani, O P
The study entitled “Field efficacy of biocapsules of entomopathogenic fungi for the management of vegetable pests” was conducted at the Biocontrol Laboratory for Crop Pest Management, Department of Agricultural Entomology, College of Agriculture, Vellayani, Thiruvananthapuram, during the year 2018-2021. The objective of the study was to evaluate the efficacy of biocapsules of Beauveria bassiana (Balsamo) Vuillemin, Metarhizium anisopliae (Metschnikoff) Sorokin, Lecanicillium lecanii (Zimmermann) Zare and Gams and Lecanicillium saksenae (Kushwaha) Kurihara and Sukarno for the management of major groups of vegetable pests. The study also intended to standardize the dose of biocapsules in managing amaranthus leaf webber Spoladea (Hymenia) recurvalis F., okra shoot and fruit borer Earias vittella F. and cowpea aphid Aphis craccivora Koch. The biocapsules of fungi were formulated at a higher spore load of 1010 with HPMC coating and chitosan as carrier, following the protocol developed by Remya and Reji (2019). In the first field experiment to evaluate the efficacy of biocapsules in managing defoliators in amaranthus, it was revealed that, Metarhizium and Beauveria capsules @ 3 L-1 sprayed twice (at weekly intervals) was effective causing 83.69 and 69.97 per cent reduction in population of S. recurvalis respectively. Lower doses of 2 and 1 capsules L -1 were less effective causing, 47.39 to 66.5 per cent reduction in larval population. Spraying spore suspensions of these fungi @ 108 mL-1 resulted in 91.27 to 100 per cent reduction, while in flubendiamide 39.35 SC, it was 89.84 per cent. Treatment with Metarhizium and Beauveria capsules did not affect the natural enemy population significantly, the mean population being 2.33 to 3.67 plant-1 . The corresponding population was 1.44 in flubendiamide 39.5 SC and 3.67 in untreated control. The yield recorded in the plots treated with Metarhizium and Beauveria capsules @ 3 L -1 was high (2.67 and 2.30 kg plot-1 ) when compared to that in untreated plot 0.80 kg plot-1 . Results of the second experiment to evaluate the efficacy of biocapsules in managing fruit and shoot borer E. vittella in okra concluded that, Beauveria capsule @ 3 L -1 and Metarhizium capsule @ 3 L-1 were equally effective when sprayed at weekly intervals leading to 84.96 and 79.64 per cent reduction in the shoot damage respectively. The percentage reduction in shoot damage was only 65.32 to 73.86 per cent reduction in lower doses of capsules. In plots treated with spore suspensions, the mean shoot damage recorded was 90 to 95 per cent. Percentage reduction in chlorantraniliprole 18.5 SC was 90.71. Considering the fruit damage, Metarhizium capsule @ 3 L-1 was found to be the best treatment causing 100 per cent reduction in damage caused by E. vittella, while it was 89.75 per cent with Beauveria capsule@ 3 L -1 . Reduction in fruit damage ranged from 67.82 to 82.81 per cent in the lower doses of capsules. Highest reduction in the fruit damage observed with spore suspensions of Beauveria and Metarhizium @ 108 mL-1 (93.16 and 100 per cent, respectively). Similar results were obtained in the case of okra leaf roller, Metarhizium @ 2 L-1 and Beauveria capsule @ 3 L -1 were found to be the best treatment causing 96.38 and 85.80 per cent reduction in population of Sylepta derogata F., while it was 80.23 per cent with Metarhizium capsule @ 3 L-1 . Reduction in population ranged from 41.35 - 68.72 per cent in the lower doses of capsules. Highest reduction in the population of S. derogata observed with spore suspensions of Beauveria and Metarhizium @ 108 mL-1 (100 per cent). Percentage reduction in chlorantraniliprole 18.5 % SC was 93.41. Treatment with biocapsules capsules did not cause any adverse affect on natural enemy population, in okra field. The yield obtained from different treatments did not vary significantly. Third experiment in cowpea field revealed that, foliar application of L. saksenae capsule @ 3 L -1 and L. lecanii capsule @ 3 L-1 were equally effective to A. craccivora when sprayed twice (at weekly intervals) causing 94.38 and 92.28 per cent reduction in the population respectively. Reduction in population noted was 57.54 to 63.96 per cent with lower dose @ 2 capsules L-1 while it was least with single capsule treatment (37.51 to 44.73 per cent). The spore suspensions were more effective resulted than the lower doses (78.73 - 83.53 per cent reduction). The chemical check thiamethoxam 25 WG recorded 95.79 per cent reduction in population. Biocapsule treatment did not affect natural enemy population significantly. The yield recorded in the plots with L. saksenae capsules @ 2 and 3 L-1 was high (1.85 and 1.56 kg plot-1 ) when compared to other treated plots and untreated plot (1- 1.45 kg plot-1 ). Therefore, it is concluded that biocapsules of Metarhizium and Beauveria, can effectively manage defoliators in amaranthus and borers in okra and those of L. lecanii and L. saksenae can be recommended for pea aphids, without affecting the natural enemies and yield significantly.
Improved formulation of lecanicillium lecanii (Zimmermann) Zare and Gams and its evaluation against sucking pests
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2015) Nithya, P R; Reji Rani, O P
Mycotoxins and enzymes of entomopathogenic fungus Lecanicillium saksenae (Kushwaha) kurihara and sukarno and their bioefficacy on crop pests
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2020) Sreeja, P; Reji Rani, O P
Novel bioformulations of entomopathogenic fungi and their efficacy aganist banana weevils
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2018) Remya, S; Reji Rani, O P
Pathogenicity and biochemical properties of entomopathogenic fungus Lecanicillium saksenae (Kushwaha) Kurihara and Sukarno
(Department of Agricultural Entomology,College of Agriculture, Vellayani, 2016) Jasmy, Y; Reji Rani, O P
The investigation entitled “Pathogenicity and biochemical properties of entomopathogenic fungus Lecanicillium saksenae (Kushwaha) Kurihara and Sukarno” was conducted at College of Agriculture, Vellayani during 2014 -2016. The objective was to study the pathogenicity and biochemical properties of L. saksenae in order to establish its virulence to insect, mite and nematode pests. L. saksenae is an indigenous isolate from the soils of Vellayani.
Pellet formulations of entomopathogenic fungi and their bioefficiacy in managing soil inhabiting pests
(Department of Entomology, College of Agriculture,Vellayani, 2024-02) Asna Sharin.; Reji Rani, O P
The study entitled “Pellet formulations of entomopathogenic fungi and their bioefficacy in managing soil inhabiting pests” was carried out at Department of Entomology, College of Agriculture, Vellayani during the year 2020-2023 with an objective to develop biopellet formulations of entomopathogenic fungi for the management of soil inhabiting insect pests. Pathogenicity test carried out in soil inhabiting pests such as pepper root mealy bug, Formicoccus polysperes Williams and later stages of cucurbit fruit fly, Bactrocera cucurbitae (Coquillett) using spore suspensions of entomopathogenic fungi such as Metarhizium anisopliae (Metsch.) Sorokin NBAIR isolate Ma4, Beauveria bassiana (Bals.) Vuillemin NBAIR isolate Bb5, B. bassiana KAU isolate ITCC 6063 and Lecanicillium saksenae (Kushwaha) Kurihara and Sukarno KAU isolate ITCC 7714 each at 108 spores mL-1 revealed that all the tested fungi were infective to pepper root mealybug, at varying levels. Apart from the normal symptoms of mycosis, L. saksenae infection resulted in sudden dissolution of the mealy coating, unlike in B. bassiana isolates, indicating its fast action. For the last instar larvae and pupae of cucurbit fruit fly, M.anisopliae was found to be the effective pathogen compared to B.bassiana isolates. Infectivity of L. saksenae was very low in fruit fly. Dose-mortality response of L. saksenae to root mealybug, F. polysperes unveiled that 107 and 108 spores mL-1 were equally effective resulting in 92 and 100 per cent mortality within four days of treatment, hence 107 spores mL-1 was determined as the effective dose. In the case of B. cucurbitae, the effective dose was 108 spores mL-1 for both larvae and pupae causing 77.5 per cent and 55 per cent mortality, respectively. The LC50 and LC90 values of L. saksenae computed on the fourth day after treatment on root mealy bug was 2.2x105 and 2.6x107 spores mL-1, respectively. The lethal time recorded for 50 per cent mortality was 23.13 h and for 90 per cent mortality it was 83.76 h, indicating its high virulence. In fruit fly larvae, for M. anisopliae, the LC50 and LC90 values were 2.5x106 and 6.6x108 spores mL-1, respectively on the 10th day after treatment, indicating a moderate virulence. Experiment to assess the effect of carrier materials on conidial viability and virulence of L. saksenae based on its germination percentage and mortality to test 125 insects revealed the superiority of the talc + chitin in the ratio 95:5 with 78.54 per cent germination and 87.5 per cent mortality of mealybugs even five weeks after storage (WAS). Other carrier materials such as talc + chitosan (90:10), talc alone and chitosan alone, exhibited only 50.62 to 74.58 per cent germination and 55.0 to 67.5 per cent mortality. The spores in chitin exhibited only 33.96 per cent viability and 50 per cent mortality. Based on conidial viability the best carrier material for formulating M. anisopliae pellets was found to be talc + chitosan in the ratio 90:10 as it recorded highest conidial viability (69.75 per cent) 5 WAS and mortality of 32.5 per cent, to the 3rd instar larvae of B. cucurbitae. When talc and talc + chitin (95:5) were used as the carrier materials the corresponding viability and mortality recorded were 61.46 to 65 and 7.5 to 20 per cent. Suitability of binding agents for formulating L. saksenae pellets was tested using various binders such as Carboxy Methyl Cellulose (CMC) 6%, Microcrystalline Cellulose (MCC) 6% and Acacia Gum arabic (AG) 5%. It was found that the combination of talc + chitin (95:5) + the binding agent CMC (6%) was superior for L. saksenae spores compared to its combination with MCC (6%) and AG (5%). CMC maintained 80.63 per cent germination and 92 per cent mortality on five WAS. The corresponding viability and mortality recorded in MCC was 51.5 and 68 per cent and in AG, it was 30.67 and 50 per cent, respectively. CMC was proved to be superior for formulating M. anisopliae pellets also, as it recorded 79.33 per cent germination and 42 per cent mortality on fifth WAS. Pellets formulated at 109 spores mL-1, using a mixture of talc + chitin (95:5) + CMC 6% were tested at varying moisture levels of 8, 10, 12 and 15%. Pellets with 15% moisture content were superior with 67.44 per cent conidial viability and 80 per cent virulence, when observed after two months. Thereafter, though there was a decrease in germination rate below 55 per cent, the virulence could be retained up to 60 per cent till three months after storage. L. saksenae pellets stored for a period of three months under ambient conditions revealed that the shelf life declined gradually after two months. After three months, conidial viability of pellets reduced from 87.25 to 38.74 per cent at 15 % 126 moisture level and from 84.99 to 32.32 per cent at 12% moisture. The mortality decreased from 90 to 60 per cent and 85 to 45 per cent in 15% and 12 % moisture levels, respectively. However, the extent of contamination noted was 2.75x105 cfu mL-1 which was beyond the permissible level as per CIBRC standards. Therefore, the pellets prepared with moisture content between 12 to 15 % where the contaminant count was within the permissible limit, 1.2x104 cfu mL-1 was fixed as ideal for pelleting. Laboratory assay carried out to standardize the dosage of L. saksenae biopellets for managing root mealybugs revealed that, 1.0 (2 pellets), 1.5 (3 pellets), 2.0 (4 pellets) and 2.5 g (5 pellets) biopellets per 100 g of soil were found to be equally effective causing 75 to 82.5 per cent mortality, two WAT. On further evaluation under pot culture, after 4 weeks of treatment the dosage 1.5 g/100g was found to be superior (74.99 per cent mortality). The corresponding mortality in chlorpyriphos 20 EC @ 0.075% was 83.33 per cent. A comparison of population density in different treatments revealed that, L. saksenae was the superior treatment as it was on par with chlorpyriphos 20 EC (0.075%). There was no population buildup upto two weeks after treatment. Hence, the dosage for pot application was fixed as 1.5 g bio pellets for 100 g of soil. The study concluded that L. saksenae biopellets, formulated at 109 spores mL-1 using talc + chitin (95:5) + 6% CMC at 12% to 15% moisture level is effective for the management pepper root mealybugs at 1.5 g of bio pellets (3 pellets) for 100 g of soil. These biopellets can be stored for a period of three months, under ambient conditions.
Pests of cabbage (Brassica oleracea L var.capitata) and cauliflower (Brassica oleracea L.var.botrytis) and their management
(Department of agricultural entomology, College of agriculture, Vellayani, 2013) Ravi, G B; Reji Rani, O P
Potential of the narural bio polymers, chitin and chitosan in pest management
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2017) Archana, N H; Reji Rani, O P
Production and evaluation of the fungus fusarium pallidorosium (coooke)saac. as a biopesticide againstpea aphid apphis craccivora koch.
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2001) Reji Rani, O P; Susamma Mathai
Tablet formulation of entomopathogenic fungus and its bioefficacy in mosquito control
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2022) Neema Dileep; Reji Rani, O P
The research work entitled ―Tablet formulation of entomopathogenic fungus and its bioefficacy in mosquito control‖ was conducted at Biocontrol Laboratory for Crop Pest Management, Department of Agricultural Entomology, College of Agriculture, Vellayani, Thiruvananthapuram, during the year 2019-2021 with an objective to develop water dispersible tablets of entomopathogenic fungus and to test their effectiveness in managing mosquitoes. Pathogenicity studies carried out using 108 spores mL-1 of Metarhizium anisopliae (Metsch.) Sorokin NBAIR isolate Ma4, Beauveria bassiana (Bals.) Vuillemin NBAIR isolate Bb5, B. bassiana KAU isolate ITCC 6063 and 107 spores mL-1 of Lecanicillium lecanii (Zimmerman) Zare and Gams NBAIR isolate Vl 8 and Lecanicillium saksenae (Kushwaha) Kurihara and Sukarno KAU isolate ITCC – 7714, revealed that all the fungi tested were infective to Anopheles, Aedes and Culex at varying levels. Infected larvae were less active at 12 hour after treatment (HAT) with sinking movement and colour change from dark grey to white. Death occurred within 24 h, with degeneration of gut. Copious amount of mucus was noticed around the body, except in L. saksenae. Infected adults were inactive and died within 24 h. The cadavers were mummified and found attached to the walls of the container. In Ma4 treated adults, white mycelial growth which turned green upon sporulation was noted 72 h after death. Observations on mortality taken at 24 h interval revealed that, M. anisopliae was the most effective fungus for mosquito control, followed by B. bassiana isolates. Lecanicillium spp. were less effective to mosquitoes. M. aniospliae was found to be superior to the biocontrol check, Bti and equivalent to the chemical check malathion 50 EC based on larval mortality. Mortality recorded by M. anisopliae was 93.33, 96.66 and 100 per cent in Anopheles, Aedes and Culex respectively, 5 days after treatment (DAT), while in Bti it was 73.33, 66.66 and 70 per cent respectively. The corresponding mortality in malathion 50 EC was 100 per cent. Based on mortality recorded in adults, M. anisopliae (83.33 and 86.66 per cent mortality) was equally effective as Bti to Anopheles and Aedes (66.66 and 76.66 per cent mortality) but inferior to malathion 50 EC that recorded complete mortality. The mortality recorded 112 in Culex was 96.66 per cent, which was on par with that recorded in malathion 50 EC (100 per cent). Dose-mortality studies of M. anisopliae on 4th instar larvae, revealed that 108 spores mL-1 was the effective dose. The LC90 values for M. anisopliae was 106 in Anopheles, Aedes and Culex. The LT90 values were 90.33, 79.46 and 55.9 h on Anopheles, Aedes and Culex, revealing that Culex is the most susceptible species. Larva was found to be the most susceptible stage for Culex, while for Anopheles and Aedes, both larva and adult were equally susceptible, whereas pupa was the least susceptible stage for all the three species. Experiment to standardize the carrier material for M. anisopliae tablets, revealed that talc + chitosan (90:10) was superior to bran, talc and bran + chitosan, as there was 71.16 per cent conidial germination and 95 per cent larval mortality in Culex on the 5th week after storage (WAS). The corresponding viability and virulence in talc were 66.33 per cent and 87.5 per cent respectively, while in bran it was 43.16 and 70 per cent and in bran + chitosan, it was 47.58 and 80 per cent, respectively. Among the binding agents tested, Carboxy Methyl Cellulose (CMC) 7% was superior to Microcrystalline Cellulose (MCC) 7%, Polyvinyl Pyrrolidone (PVP) 5% and Acacia Gum Arabic (AG) 5% as it maintained 62.66 per cent germination and 95 per cent mortality on 5 WAS. The tablets of M. anisopliae @ 1010 spores mL-1, formulated using talc + chitosan + CMC 7% at varying moisture levels of 8, 10 and 15 % when subjected to shelf life studies revealed that tablets formulated at 15 % were superior in viability (65.06 per cent) and virulence (88 per cent mortality) at 8 WAS. Thereafter, though there was a decrease in germination rate below 60 per cent, the virulence could be maintained up to 72 per cent till three months of storage. Extent of contamination noticed was significantly high (105 cfu mL-1) in 15 % moisture compared to 104 in 8 and 10 % moisture levels. However, 105 being the permitted level of contaminants as per CIBRC standards, 15% was fixed as the ideal moisture content for formulating tablets. The effective shelf life was therefore determined as three months under ambient conditions. 113 The tablets when tested for their bioefficacy to Culex larvae revealed that 3 and 4 tablets L-1 were equally effective causing 82 and 83 per cent mortality within 9 DAT, under laboratory conditions. The adult emergence from the treated larvae was 17 and 16 per cent for 3 and 4 tablets L-1, which was significantly lower than that from control (81 per cent). Under field conditions, 9 and 10 tablets 10 L-1 exhibited similar level of mortality (83.97 and 84.1 per cent) compared to 7 and 8 (75.03 and 79.59 per cent). Therefore 9 tablet 10 L-1 was fixed as the effective dosage for treating stagnant water bodies. It is concluded that water dispersible tablets of M. anisopliae formulated at 1010 spores mL-1 with talc + chitosan + CMC (7%) at 15% moisture is effective for the management of mosquito larvae in stagnant water bodies @ 9 tablets 10 L-1. They can be stored effectively for three months with 72 per cent virulence, under ambient conditions.
Tolerance of entomopathogenic fungi Lecanicillium saksenae(Kushwaha) Kurihara and Sukarno and Lecanicillium lecanii (Zimm.) Zare and Gams to abiotic stress
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2022-11-09) Tejaswi G Gowda.; Reji Rani, O P
The study entitled “Tolerance of entomopathogenic fungi Lecanicillium saksenae (Kushwaha) Kurihara and Sukarno and Lecanicillium lecanii (Zimm.) Zare and Gams to abiotic stress” was conducted at Department of Agricultural Entomology, College of Agriculture, Vellayani, Thiruvananthapuram, during the period 2017-22. The objective of study was to assess the tolerance level of L. saksenae and L. lecanii to insecticides, fungicides, temperature and UV radiation and explore the possibilities of developing tolerant strains. Results of the experiment to study the tolerance of L. saksenae and L. lecanii to insecticides revealed that the new generation insecticides viz., flubendiamide 39.35% SC, chlorantraniliprole 18.5% SC, imidacloprid 17.8% SL and thiamethoxam 25% WG were compatible with both the fungi in half dose, recommended dose and double the recommended doses. Among the old generation insecticides, only dimethoate 30% EC was found to be compatible at half and recommended doses. Malathion 50% EC, quinalphos 25% EC and chlorpyrifos 20% EC were found to be toxic to both the fungi at all the test doses. Among all the insecticides quinalphos 25% EC was found to be highly toxic with a Biological Index (BI) of 14 to 22. Among the fungicides tested, azoxystrobin 23% SC was found to be compatible with L. saksenae and it was moderately toxic to L. lecanii. Copper oxychloride 50% WP was found to be moderately toxic to L. lecanii and toxic to L. saksenae. Carbendazim 50 % WP, mancozeb 75% WP, hexaconazole 5% EC and tebuconazole 25 % EC were found to be toxic to both the fungi based on BI values. Artificial selection to induce tolerance to incompatible insecticides and fungicides was attempted by subculturing fungi in respective poisoned media for ten successive generations. No improved strain could be developed for quinalphos tolerance in both the fungi. Induction of fungicide tolerance resulted in two tolerant 183 strains in L. saksenae but no improved strain could be developed in L. lecanii. Hexaconazole tolerant strain of L. saksenae was able to tolerate the recommended field dose (0.15 %). Carbendazim tolerant strain exhibited increase in growth, sporulation and germination at the recommended dose (0.2%) compared to those in the non-selected culture. REP-PCR data revealed the genotypic variation of the strains. The variation quantified based on Jaccard’s coefficient analysis revealed that carbendazim tolerant strain and hexaconazole tolerant strain were 42 per cent and 38 per cent dissimilar from mother culture. Temperature tolerance study carried out at varying regimes of 30, 32, 34, 36, 38 and 40 oC (8h exposure) revealed that increase in temperature significantly affected the growth parameters of both the fungi. Growth of L. lecanii and L. saksenae was completely inhibited at 36 and 40 oC, respectively. In terms of sporulation, no exponential reduction (>10 7 spores mL-1 ) was observed till 34 o C in L. saksenae, while in L. lecanii it was reduced to 105 spores mL-1 and it was terminated at 36 oC. Comparative tolerance between the species revealed that L. saksenae performed better than L. lecanii. No significant reduction (<15 per cent) in terms of germination was observed in L. saksenae till 36 oC, while in L. lecanii more than 70 per cent reduction was observed at 34 oC. L. saksenae spores were able to germinate till 40 oC while in L. lecanii germination was completely inhibited at this temperature. Attempts to induce temperature tolerance by subculturing the fungi at highest tolerant temperature for ten generations did not yield any tolerant strain. UV tolerance study conducted with two irradiances wave length viz., UVA - 365 nm and UVB - 290 to 315 nm for 10, 20, 30 min, 1h, 2h, 3h and 4h exposure durations, revealed that the growth of both the fungi was not significantly affected when exposed for shorter durations (10, 20 and 30 min), whereas when exposed for longer durations (1, 2, 3 and 4h), there was significant reduction in growth. In both the wave lengths and across the exposure durations, L. saksenae exhibited higher colony growth than L. lecanii. In UVA irradiance, the growth reduction ranged 184 between 13 to 75 per cent in L. saksenae and it was 23 to 81 per cent in L. lecanii. In UVB irradiance, colony reduction was between 12 to 85 per cent in L. saksenae and 31to 89 per cent in L. lecanii. In terms of sporulation, no exponential reduction was observed in both the fungi. There was germination inhibition in both the fungi exposed to UVA and UVB irradiance. In shorter exposures, L. lecanii exhibited higher germination (30 to 51 per cent) while in longer exposures L. saksenae exhibited higher germination (13 to 16 per cent). UV mutagenesis resulted in two UV mutants one each in L. saksenae and L. lecanii. L. lecanii mutant was named as LlUVM1 and L. saksenae mutant was named as LsUVM. Both the mutants were superior in terms of growth parameters when tested under UVA and UVB irradiance when compared to their mother culture. The REP-PCR analysis revealed that UV mutants LsUVM and LlUVM1 varied genotypically from the mother culture. Based on Jaccard’s coefficient there was 32 per cent dissimilarity with their respective mother cultures. Bioassay carried out to study the effect of artificial selection on the pathogenicity of fungicide tolerant strains of L. saksenae on rice bug Leptocorisa oratorius Fab. revealed that spore suspensions of carbendazim and hexaconazole tolerant strains of L. saksenae (107 spores mL -1 ) in the presence of respective fungicide, exhibited higher virulence than the mother culture. Mortality caused by the tank mix formulation of carbendazim tolerant strain + 0.2 % carbendazim 50 % WP caused 86.67 per cent mortality, while its mother culture resulted in 36.67 per cent mortality. Hexaconazole tolerant strain caused 60 per cent mortality while the mother culture did not cause mortality with tank mix of hexaconazole 5 % EC 0.15 %. Pathogenicity assay of L. saksenae UV mutant revealed that there was no significant difference in mortality of L. oratorius between the mother culture and the mutant. In L. lecanii the UV mutant (LlUVM1) exhibited higher virulence on the 185 brinjal mealybug, Coccidohystrix insolita Green. LlUVM1 caused 100 per cent mortality on the eighth day, while the mother culture of L. lecanii caused 83.75 per cent mortality. Therefore, the study concludes that the indigenous isolate L. saksenae is comparatively more tolerant to insecticides, temperature and UV exposure than L. lecanii. Strains of L. saksenae developed for carbendazim and hexaconazole tolerance performed better in terms of phenotypic characters. Genotypically, they expressed variation of 42 and 38 per cent respectively from mother culture. The UV tolerant strain developed in both the species were superior to the mother culture under UV irradiance. The findings pave way to the utilization of the indigenous isolate of L. saksenae and its fungicide tolerant mutants and the UV mutant of L. lecanii in pest management as they can combat abiotic stress in prevailing climatic conditions.
Tolerance of entomopathogenic fungi Lecanicillium saksenae(Kushwaha) Kurihara and Sukarno and Lecanicillium lecanii (Zimm.) Zare and Gams to abiotic stress
(Department of Agricultural Entomology, College of Agriculture, 2022-11-09) Tejaswi G Gowda.; Reji Rani, O P
The study entitled “Tolerance of entomopathogenic fungi Lecanicillium saksenae (Kushwaha) Kurihara and Sukarno and Lecanicillium lecanii (Zimm.) Zare and Gams to abiotic stress” was conducted at Department of Agricultural Entomology, College of Agriculture, Vellayani, Thiruvananthapuram, during the period 2017-22. The objective of study was to assess the tolerance level of L. saksenae and L. lecanii to insecticides, fungicides, temperature and UV radiation and explore the possibilities of developing tolerant strains. Results of the experiment to study the tolerance of L. saksenae and L. lecanii to insecticides revealed that the new generation insecticides viz., flubendiamide 39.35% SC, chlorantraniliprole 18.5% SC, imidacloprid 17.8% SL and thiamethoxam 25% WG were compatible with both the fungi in half dose, recommended dose and double the recommended doses. Among the old generation insecticides, only dimethoate 30% EC was found to be compatible at half and recommended doses. Malathion 50% EC, quinalphos 25% EC and chlorpyrifos 20% EC were found to be toxic to both the fungi at all the test doses. Among all the insecticides quinalphos 25% EC was found to be highly toxic with a Biological Index (BI) of 14 to 22. Among the fungicides tested, azoxystrobin 23% SC was found to be compatible with L. saksenae and it was moderately toxic to L. lecanii. Copper oxychloride 50% WP was found to be moderately toxic to L. lecanii and toxic to L. saksenae. Carbendazim 50 % WP, mancozeb 75% WP, hexaconazole 5% EC and tebuconazole 25 % EC were found to be toxic to both the fungi based on BI values. Artificial selection to induce tolerance to incompatible insecticides and fungicides was attempted by subculturing fungi in respective poisoned media for ten successive generations. No improved strain could be developed for quinalphos tolerance in both the fungi. Induction of fungicide tolerance resulted in two tolerant 183 strains in L. saksenae but no improved strain could be developed in L. lecanii. Hexaconazole tolerant strain of L. saksenae was able to tolerate the recommended field dose (0.15 %). Carbendazim tolerant strain exhibited increase in growth, sporulation and germination at the recommended dose (0.2%) compared to those in the non-selected culture. REP-PCR data revealed the genotypic variation of the strains. The variation quantified based on Jaccard’s coefficient analysis revealed that carbendazim tolerant strain and hexaconazole tolerant strain were 42 per cent and 38 per cent dissimilar from mother culture. Temperature tolerance study carried out at varying regimes of 30, 32, 34, 36, 38 and 40 oC (8h exposure) revealed that increase in temperature significantly affected the growth parameters of both the fungi. Growth of L. lecanii and L. saksenae was completely inhibited at 36 and 40 oC, respectively. In terms of sporulation, no exponential reduction (>10 7 spores mL-1 ) was observed till 34 o C in L. saksenae, while in L. lecanii it was reduced to 105 spores mL-1 and it was terminated at 36 oC. Comparative tolerance between the species revealed that L. saksenae performed better than L. lecanii. No significant reduction (<15 per cent) in terms of germination was observed in L. saksenae till 36 oC, while in L. lecanii more than 70 per cent reduction was observed at 34 oC. L. saksenae spores were able to germinate till 40 oC while in L. lecanii germination was completely inhibited at this temperature. Attempts to induce temperature tolerance by subculturing the fungi at highest tolerant temperature for ten generations did not yield any tolerant strain. UV tolerance study conducted with two irradiances wave length viz., UVA - 365 nm and UVB - 290 to 315 nm for 10, 20, 30 min, 1h, 2h, 3h and 4h exposure durations, revealed that the growth of both the fungi was not significantly affected when exposed for shorter durations (10, 20 and 30 min), whereas when exposed for longer durations (1, 2, 3 and 4h), there was significant reduction in growth. In both the wave lengths and across the exposure durations, L. saksenae exhibited higher colony growth than L. lecanii. In UVA irradiance, the growth reduction ranged 184 between 13 to 75 per cent in L. saksenae and it was 23 to 81 per cent in L. lecanii. In UVB irradiance, colony reduction was between 12 to 85 per cent in L. saksenae and 31to 89 per cent in L. lecanii. In terms of sporulation, no exponential reduction was observed in both the fungi. There was germination inhibition in both the fungi exposed to UVA and UVB irradiance. In shorter exposures, L. lecanii exhibited higher germination (30 to 51 per cent) while in longer exposures L. saksenae exhibited higher germination (13 to 16 per cent). UV mutagenesis resulted in two UV mutants one each in L. saksenae and L. lecanii. L. lecanii mutant was named as LlUVM1 and L. saksenae mutant was named as LsUVM. Both the mutants were superior in terms of growth parameters when tested under UVA and UVB irradiance when compared to their mother culture. The REP-PCR analysis revealed that UV mutants LsUVM and LlUVM1 varied genotypically from the mother culture. Based on Jaccard’s coefficient there was 32 per cent dissimilarity with their respective mother cultures. Bioassay carried out to study the effect of artificial selection on the pathogenicity of fungicide tolerant strains of L. saksenae on rice bug Leptocorisa oratorius Fab. revealed that spore suspensions of carbendazim and hexaconazole tolerant strains of L. saksenae (107 spores mL -1 ) in the presence of respective fungicide, exhibited higher virulence than the mother culture. Mortality caused by the tank mix formulation of carbendazim tolerant strain + 0.2 % carbendazim 50 % WP caused 86.67 per cent mortality, while its mother culture resulted in 36.67 per cent mortality. Hexaconazole tolerant strain caused 60 per cent mortality while the mother culture did not cause mortality with tank mix of hexaconazole 5 % EC 0.15 %. Pathogenicity assay of L. saksenae UV mutant revealed that there was no significant difference in mortality of L. oratorius between the mother culture and the mutant. In L. lecanii the UV mutant (LlUVM1) exhibited higher virulence on the 185 brinjal mealybug, Coccidohystrix insolita Green. LlUVM1 caused 100 per cent mortality on the eighth day, while the mother culture of L. lecanii caused 83.75 per cent mortality. Therefore, the study concludes that the indigenous isolate L. saksenae is comparatively more tolerant to insecticides, temperature and UV exposure than L. lecanii. Strains of L. saksenae developed for carbendazim and hexaconazole tolerance performed better in terms of phenotypic characters. Genotypically, they expressed variation of 42 and 38 per cent respectively from mother culture. The UV tolerant strain developed in both the species were superior to the mother culture under UV irradiance. The findings pave way to the utilization of the indigenous isolate of L. saksenae and its fungicide tolerant mutants and the UV mutant of L. lecanii in pest management as they can combat abiotic stress in prevailing climatic conditions.