Radha R

Bio: Radha R is an academic researcher. The author has contributed to research in topics: Callosobruchus maculatus & Agriculture. The author has an hindex of 2, co-authored 9 publications receiving 21 citations.

Efficacy of plant extracts on the toxicity, ovipositional deterrence and damage assessment of the cowpea weevil, Callosobruchus maculatus (Coleoptera: Bruchidae)

Abstract: A laboratory experiment was conducted to investigate the efficacy of different plant derivatives against the development of the cowpea weevil, Callosobruchus maculatus (F) (Coleoptera: Bruchidae)fed on cowpea, Vigna unguiculata (W) seeds. The leaf extracts of romatic plants, Murraya koenigii and Azadirachta indica (A.Juss) were evaluated for their growth, adult mortality and oviposition inhibition of C. maculatus. The results revealed that the extracts of the two plant species caused a considerable reduction in the number of weevils. The combination of neem seed kernel extract and leaf extract of M. koenigii was the most effective in checking insect infestation and allowing the least number of F1 adults to emerge from the seeds over other treatments. Acetone leaf extracts of M. koenigii were more toxic to adult beetles compared to ethanolic extracts. Thus, the botanicals acted as insect antifeedant and the order of toxicity of various treatments on cowpea weevil were: combination of neem seed kernel extract + M. koenigii leaf extract > neem > M. koenigii.

Evaluation of larvicidal action of natural extracts on mosquito larvae of Aedes aegypti (Diptera: Culicidae)

Abstract: Mosquitoes are known to cause more diseases than any other group of arthropods and affect millions of people throughout the world. The current study was aimed to investigate larvicidal potential of three natural extracts such as aloe vera and onion, alcohol and cloves, marigold and garlic against the dengue vector, Aedes aegypti. Insecticidal susceptibility tests were carried out using WHO standard method and the mortality was observed after 24-h exposure. All the tested extracts showed moderate to good larvicidal activities. However, the maximum larval mortality was observed in the extract of the alcohol and cloves that showed high efficacy on the Aedes mosquito larva. The findings of the present studies suggested that the use of aloe vera, onion and garlic has a strong effect in acting as a mosquito larvicide and the natural plant extracts can be prepared at home and used at any cost of time which is feasible for the masses.

Comparative Studies on the Butterfly Diversity and Species Richness in Selected Agricultural Fields in Tamil Nadu

Abstract: Butterflies are valued components of grassland ecosystems both for their aesthetic nature and they provide as pollinators of the ecosystem services. Loss and fragmentation of native habitats, along with other disturbances associated with intensive agriculture can have dramatic effects on butterfly communities. The close link between butterflies and their natural environment make them good candidates for use as ecological indicators. Hence an attempt has been made to study the diversity and pollination tendencies of butterflies between organic crop fields and pesticide sprayed crop fields. The research was set out to establish whether organic and conventional farming systems support different levels of pest and non-pest butterflies. In the present study maximum insect abundance and total number of individuals were recorded in organic fields. The study also proved that organic farming practices can help in the population build-up of natural enemies and pollinators. However there was remarkable difference in Shannon index and Simpson index of diversity between organic and chemical fields. Phytophagous insect populations were very low in number in organic farms. Hence organic farming practices may encourage natural enemies' diversity and may not be favourable for pests.

Studies on the Levels of Cholesterol and Phospholipids in the Haemolymph of the Lepidopteran Larvae before and after Stinging by the Potter Wasp, Eumenes Conica

Abstract: The potter wasp, Eumenes conica is a solitary larval endoparasitoid, which feeds on host haemolymph of lepidopteran larva during its internal phase. The wasp first constructs the nest, hunts for its prey, the caterpillars, stings the prey, paralyses it and then brings them to the nest which is probably a very highly specialized behaviour. The present study was conducted to determine the levels of cholesterol and phospholipids in the haemolymph of the lepidopteran larvae before and after stinging by the wasp, Eumenes conica.The parasitization of the wasp affect the nutritional physiology of the larva and cause a reduced uptake of food and an increase in the concentration of free sugars in the haemolymph and of glycogen in whole body. The parasitoid larva, causes a reduction of proteins in the host’s plasma and an accumulation of lipids in whole body. Dilution of host haemolymph led to a reduced concentration of lipid in parasitoid larvae and a reduced survival rate. Thus, a sufficient concentration of nutrients in the host’s haemolymph appears to be crucial for successful parasitoid development.

Bruchid pest management in pulses: past practices, present status and use of modern breeding tools for development of resistant varieties

Abstract: Bruchids (Callosobruchus spp.) are recognised as the most detrimental storage pest of pulses, especially in the tropics and subtropics. They invade matured pods as well as seeds during storage and, to some extent, farming fields, in turn reducing the net yield of the crops. Several approaches including cultural, biological, physical and chemical control measures have been implemented with the aim of managing these pests, but none of these have been successful across time and space. Recently, transgenic- and marker-assisted breeding approaches have appeared as promising tools for the successful management of these pests. Although some efforts have been made on the development of bruchid-resistant transgenic crops, the cultivars developed are yet to be commercialised worldwide because of various limitations. In contrast, marker-assisted breeding involving the identification of DNA-based markers linked to host resistance against bruchids, have shown some success in the quest for the development of bruchid-resistant cultivar(s). DNA markers linked to bruchid resistance have been identified in various grain legumes, particularly in the genus Vigna, and include mung bean (Vigna radiata), azuki bean (Vigna angularis), rice bean (Vigna umbellata), cowpea (Vigna unguiculata) and black gram (Vigna mungo). After their validation in different genetic backgrounds, these markers could be utilised for marker-assisted selection and breeding ventures to protect pulse crops. The present study discusses the pros and cons of different approaches for the successful management of the bruchid pests in pulses. The review also highlights about the integrative approach aided with molecular interventions to improve productivity by avoiding losses incurred due to bruchids, and to attain sustainable yields for major pulse crops.

Entomo Toxicity of Xylopia Aethiopica and Aframomummelegueta in Suppressing Oviposition and Adult Emergence of Callasobruchus Maculatus ( Fabricus ) ( Coleoptera : Chrysomelidae ) Infesting Stored Cowpea Seeds

Abstract: The cowpea beetle, Callosobruchus maculatus (Fabricus) (Coleoptera: Chrysomelidae), is a major pest of stored cowpea militating against food security in developing nations. The comparative study of Xylopia aethiopica and Aframomum melegueta powder in respect to their phytochemical and insecticidal properties against C. maculatus was carried out using a Complete Randomized Design (CRD) with five treatments (0, 1.0, 1.5, 2.0 and 2.5g/20g cowpea seeds corresponding to 0.0, 0.05, 0.075, 0.1 and 0.13% v/w) replicated thrice under ambient laboratory condition (28±2°C temperature and 75±5% relative humidity). The phytochemical screening showed the presence of flavonoids, saponins, tannins, cardiac glycoside in both plants, while alkaloids was present in A. melegueta and absent in X. aethiopica. The mortality of C. maculatus increased gradually with exposure time and dosage of the plant powders. X. aethiopica caused 75.15% adult mortality and A. meleguta exerted 85% mortality at 120 hrs post infestation. Maximum oviposition deterrent activity was observed with X. aethiopica (54.26%) compared to A. melegueta (51.32%). Conclusively, both plants showed highly useful bioactivity against C. maculatus in suppressing oviposition and adult emergence and, therefore, can be used in formulating ecofriendly herbal insecticides.

Effect of Mining Activities on Vegetation Composition and nutrient status of Forest Soil in Benue Cement Company, Benue State, Nigeria

Abstract: Mining is essential in the economic development plan of any country endowed with mineral resources. This is due to both internal and external economic benefits that are made available to countries that are involved in the extraction of mineral resources. Internally, there is creation of employment and revenue generation among others while externally; a substantial foreign exchange is available to such countries. However, looking at the socio-economic importance of the industry, most countries lose sight of the ensuing effect that might accrue to an area as a result of mining activities. This study sought to provide an empirical data to ascertain whether or not mining activities has affected tree diversity of the area in general and on vegetation and soil nutrients in particular. In the study diversity indices (Shannon, margalef and Pielou's evenness) all indicated higher values for adjacent site 5 km away from the factory. Soil health indicators investigated revealed significant differences except Potassium, with adjacent site having higher mean values. This study has indicated that tree diversity was higher in the adjacent site and also that soil 5 km away from the factory was healthier than soil within factory site. Construction of shield over factory site is suggested.

Preparation of Ecofriendly Formulations Containing Biologically Active Monoterpenes with Their Fumigant and Residual Toxicities against Adults of Culex pipiens

Abstract: Different mixtures of monoterpenes (ketone, alcohol, and alkene) were loaded on paper discs and wax and their knockdown activities were evaluated against Culex pipiens adults. Some individual monoterpenes were also evaluated by residual toxicity technique. Citronella oil as a reference was also loaded separately or in combination with monoterpenes on paper discs and wax. The ketone monoterpenes mixture (camphor, menthone, carvone, and fenchone) on paper discs was the most active (KT50 = 17.20 min) followed by ketone monoterpenes with citronella oil (KT50 = 20.79 min) and citronella oil alone (KT50 = 28.72 min). Wax formulations proved that the ketone and alcohol (geraniol, thymol, and menthol) monoterpenes gave the most activity as knockdown (KT50 = 31.79 and 43.39 min, resp.). Alcohol monoterpenes formulation recorded KT50 = 43.39 min. Residual activity of tested individual monoterpenes reported that the menthol was more toxic than camphor and camphene. Generally, this study suggests that the monoterpenes have the properties, which make them used as eco-friendly compounds in the control programs of Cx. pipiens adult. The use of paper discs is more applicable than wax in the adulticidal formulations.