Karthik, R S
Efficacy and biosafety evaluation of the entomopathogenic fungus Lecanicillium saksenae (Kushwaha) Kurihara and Sukarno - Vellayani Department of Agricultural Entomology, College of Agriculture 2025 - 103p.
Ph.D
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.
Agricultural Entomology
Biosafety evaluation
Entomopathogenic fungus
Lecanicillium saksenae
Kurihara
Sukarno
632.6 / KAR/EF Ph.D
Efficacy and biosafety evaluation of the entomopathogenic fungus Lecanicillium saksenae (Kushwaha) Kurihara and Sukarno - Vellayani Department of Agricultural Entomology, College of Agriculture 2025 - 103p.
Ph.D
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.
Agricultural Entomology
Biosafety evaluation
Entomopathogenic fungus
Lecanicillium saksenae
Kurihara
Sukarno
632.6 / KAR/EF Ph.D