Browsing by Author "R. Dhanapal"

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Exploration of indigenous strains of the green muscardine fungus from soils and their pathogenicity against the tobacco caterpillar, Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae)
(Springer, 2020) R. Dhanapal; D. V. Sai Ram Kumar; R. Lakshmipathy; C. Sandhya Rani; V. Manoj Kumar
In the recent years, the keen interest has been increased towards biological control-based management practices using entomopathogenic fungi (EPF) for the control of many economically important insects. In this management practices, selection of right strains of EPF is an important criteria to control the target pests in effective manner. In this context, this research work was formulated to find out environmentally effective strains of EPF in the soils of costal districts of Andhra Pradesh. Out of 135 soil samples collected, 8 soil samples yielded 8 strains of Metarhizium anisopliae. Among all 8 M. anisopliae isolates, the least median lethal concentration (LC50) for 2nd instar of the tobacco caterpillar, Spodoptera litura (Lepidoptera: Noctuidae) was 1.24 × 105 spores ml-1 in M-7, followed by 1.72 × 105 spores ml-1 in M-5 and 1.86 × 105 spores ml-1 in M-4 in an increasing order. Likewise, the median lethal time (LT50) values of different isolates of EPF against 2nd instar of S.litura were calculated for a uniform highest dose of 1 × 108 spores ml−1. Among all 8 M. anisopliae isolates, the lowest LT50 was observed as 186.44 hours post infection (hpi) with M-5 and 189.34 hpi with M-7. © 2020, The Author(s).
Improving Insect Control Using Genetically Modified Entomopathogens
(Springer Nature, 2022) R. Dhanapal; Achanta Sravika; S. Sekar; S. Ramesh Babu; M. Gajalakshmi
Entomopathogens, employed as biological control, were formulated as eco-friendly substitutes for chemical insecticide. Nevertheless, microbial-based insecticides were implicated to be commercially inadequate based on their indiscriminate efficacy and low virulence. The resistance, pathogenicity, and virulence of entomopathogens to adverse conditions were greatly enhanced by genetic engineering. Improvement of virulence was achieved by modifying entomopathogens to express insecticidal proteins/peptides. The continued use of synthetic chemical insecticides remains an apprehension by the public as well as their approval of genetically modified organisms including inventive biological insecticides which provide diverse beneficial and environmentally sustainable options to control insect pests. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022.
Isolation of indigenous strains of the white halo fungus as a biological control agent against 3rd instar larvae of tobacco caterpillar, Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae)
(Springer, 2020) R. Dhanapal; D. V. Sai Ram Kumar; R. Lakshmipathy; C. Sandhya Rani; V. Manoj Kumar
The farmer interest in biological control-based management practices using entomopathogenic fungi (EPF) for the control of many economically important insects has increased. In this process, selection of effective strains of EPF is an important criterion to control the target insect pests in efficient manner. In this context, this research work was formulated to find out environmentally effective strains of EPF in the soils of costal districts of Andhra Pradesh, India. Out of 135 soil samples collected, 9 yielded 9 strains of Lecanicillium lecanii. Among all 9 L. lecanii isolates, the least median lethal concentration (LC50) for 3rd instar larvae of the tobacco caterpillar, Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae), was 1.17 × 106 spores ml−1 in L-8, followed by 1.27 × 106 spores ml−1 in L-5 in an increasing order. Likewise, the median lethal time (LT50) values of different isolates of EPF against the 3rd instar of S. litura were calculated for the uniform highest concentration of 1 × 108 spores ml−1. Among all 9 L. lecanii isolates, the lowest median lethal time (LT50) was observed as 7.70 days by L-8, followed by 7.77 days by L-5 and 8.50 days by L-7. © 2020, The Author(s).
Storage of chickpea grains (Cicer arietinum L.) in triple layer bags prevent losses caused by Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae) under laboratory conditions
(Elsevier Ltd, 2020) S. Ramesh Babu; S.V.S. Raju; R. Dhanapal; Kamal Ravi Sharma
Present study envisages the potential of triple layer bags for reducing pulse beetle infestation under laboratory conditions over six months of storage. It was observed that when chickpea grain was stored in jute bags with bruchid infestation, the germination percentage decreased significantly from 84.67 to 18.67% in six months of storage. But, the grain stored in jute bags without infestation the germination percentage decreased from 92.00 to 73.33% only. On the other hand, grains stored in triple layer bags with bruchid infestation, the germination percentage merely decreased from 86.00 to 78.33% in six months of storage and triple layer bags without infestation the germination percentage only decreased from 91.67 to 90.67%. The per cent grain damage over a period of six months storage also increased significantly from 14.54 to 70.67% and 0.00–26.45% in jute bag with bruchid infestation and jute bag without infestation, respectively. However, per cent grain damage in triple layer bags with bruchid infestation increased only from 15.15 to 25.70% and triple layer bags without bruchid infestation showed negligible increase from 0.00 to 2.64% grain damage in six months of storage. The corresponding per cent weight loss of infested grain was increased significantly from 8.51 to 55.67% in six months of storage in jute bag with bruchid infestation and from 0.00 to 15.08% in jute bag without infestation. Whereas, per cent weight loss of infested grain in triple layer bags with bruchid infestation increased only from 7.83 to 15.70 in six months of storage and triple layer bags without bruchid infestation recorded a mere per cent increase in weight loss from 0.00 to 1.48%. Benefit cost ratio showed that grains stored in triple layer bags for 6 months has highest benefit cost ratio (1.23) compared to jute bag storage (0.39). © 2020 Elsevier Ltd