Antimicrobial Activity of Melia azedarach Against Porphyromonas gingivalis, Acute Oral Toxicity Characterization and Development of DNA Minibarcode Based Markers for Identification from Allied Plants

Rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae), is one of the most widely distributed destructive pests of stored rice and wheat grains.Synthetic insecticides and fumigants are predominately used to control this pest.However, wide use of these chemicals manifest pesticidal residues and pest resistance necessitating to look for some other environmental-friendly alternatives such as nano-formulated botanical extracts.This study evaluated nano-formulated leaf extracts of some promising plant species against S. oryzae adults.Initial screening of the acetone extracts of neem (Azadirachta indica A. Juss.), guava (Psidium guajava L.), dhraik (Melia azedarach L.), tobacco (Nicotiana tabacum L.) and eucalyptus (Eucalyptus camaldulensis Dehn.) using grain treatment bioassay method showed maximum and significant weevil mortality by the extracts of A. indica and P. guajava i.e. 98 and 94%, respectively at 120 h postexposure.These extracts were further nano-formulated using silver nitrate (AgNO 3 ).Toxicity and repellency of different concentrations (i.e. 10, 5, 2.5 and 1.25%) of these nano-formulated extracts were determined against S. oryzae weevils.Results showed significant mortality of the exposed weevil individuals by all treatments and this mortality response was directly proportional to the extract concentration and exposure time.Nano-formulated A. indica extract showed highest mortality (98.7%), followed by M. azedarach (97%), N. tabacum (96%) and P. guajava (84%) at 96 h post-exposure.Probit analysis exhibited minimum LC 50 for A. indica (0.62%), followed by P. guajava (0.66%), N. tabacum (0.71%) and M. azedarach (0.94%) at 96 h post-exposure.In case of repellency, 10% concentration of the nano-formulated N. tabacum extract exhibited highest repellency (54%), followed by M. azedarach (48%) and P. guajava (28%) after 24 h of exposure.Overall study results demonstrated the effectiveness of these nano-formulated phytoextracts against S. oryzae advocating their integration in eco-friendly management of stored grain insect pests.