Chemical composition and mosquitocidal properties of essential oil from Indian indigenous plants Ocimum tenuiflorum L. and Ocimum americanum L. against three vector mosquitoes.

Mosquitoes stand out as the most perilous and impactful vectors on a global scale, transmitting a multitude of infectious diseases to both humans and other animals. The primary objective of the current research was to assess the effectiveness of EOs from Ocimum tenuiflorum L. and Ocimum americanum L. in controlling Anopheles stephensi Liston. Culex quinquefasciatus Say and Aedes aegypti L. mosquitoes. The larvae, pupae and eggs of the mosquitoes were exposed to four different concentrations (6.25-50 ppm). The tested EOs resulted in >99-100 % mortality at 120 h for the eggs of all examined mosquito species. It also showed robust larvicidal and pupicidal activity with LC50 and LC90 values of 17-39, 23-60 ppm and 46-220, and 73-412 ppm against Aedes, Culex and Anopheles mosquito species, respectively, at 24 h of treatment. The Suitability Index or Predator Safety Factor demonstrated that the EOs extracted from O. tenuiflorum L. and O. americanum L. did not cause harm to P. reticulata, D. indicus (water bug), G. affinis and nymph (dragonfly). GC-MS analysis identified the major probable constituents of the oil, including Phenol, 2-Methoxy-4-(1-Propenyl)- (28.29 %); 1-Methyl-3-(1'-Methylcyclopropyl) Cyclopentene (46.46 %); (E,E,E)-3,7,11,15-Tetramethylhexadeca-1,3,6,10,14-Pentaene (18.91 %) and 1,3-Isobenzofurandione, 3a,4,7,7a-Tetrahydro-4,7-Dimethyl (33.02 %). These constituents may play a significant role in the mosquitocidal activity of the oil. The same results were identified in the formulation prepared from the EOs. This marks the first report confirming the successful utilization of EOs derived from O. tenuiflorum L. and O. americanum L. in mosquito population control initiatives.

Larvicidal, Ovicidal, and Histopathological Effects of the Sulphur Polypore Mushroom, Laetiporus sulphureus (Agaricomycetes), Collected from Tamil Nadu, India against Mosquitoes.

This study was conducted to determine the mosquitocidal activity of 6 species of higher Basidiomycetes collected from various places in the state of Tamil Nadu, India. The mushrooms were identified using MycoKey MMI software. We used morphological characteristics such as size, color, height, width (of the cap, lamellae, stipe, and fruiting body), spore deposits, and the presence or absence of ring to identify species. Eggs and larvae of Culex quinquefasciatus and Anopheles stephensi were exposed to various concentrations (62.5, 125.0, 250.0, and 500.0 ppm) of extracts from the 6 mushrooms. The extracts were dissolved in dimethyl sulfoxide. Among the 6 mushrooms, the methanol extract of Laetiporus sulphureus showed high toxicity toward mosquitoes at different life stages, with 96% larvicidal activity against A. stephensi and 76% activity against C. quinquefasciatus. After 24 hours, we found half-maximal lethal concentrations of 155.862 ppm for A. stephensi and 227.225 ppm for C. quinquefasciatus, and 90% lethal concentrations of 424.128 ppm for A. stephensi and 1011.663 ppm for C. quinquefasciatus. The extracts also showed strong ovicidal activity against mosquito eggs: 100% activity against A. stephensi and 91% activity against C. quinquefasciatus were observed at an extract concentration of 500 ppm 120 hours after treatment. The methanol extract of L. sulphureus was tested for toxicity against a nontarget organism, but we found none. Histopathological studies of the treated larvae revealed serious damage to cells in the midgut. These results suggest that the methanol extract of L. sulphureus is a good natural source for controlling mosquitoes.

Comparative studies of tripolyphosphate and glutaraldehyde cross-linked chitosan-botanical pesticide nanoparticles and their agricultural applications.

A nanopesticide formulation was developed using chitosan and a botanical pesticide PONNEEM® and its antifeedant, larvicidal and growth regulating activities were screened against Helicoverpa armigera, a major lepidopteran pest. Chitosan nanoparticles (CSNs) were prepared by using two different cross-linking agents namely glutaraldehyde (GLA) and tripolyphosphate (TPP). The effects of cross linking agents on CSNs and the biological properties against the insect pest were also studied. Cross linking of chitosan with either TPP or GLA was confirmed through Fourier Transform Infrared (FTIR) spectroscopy. Electron micrograph revealed that the size of CSNs varied from 32 to 90nm. The stability of nanoparticles lasted for 9days in CSNs-TPP-PONNEEM. In CSNs-GLA-PONNEEM, the stability of nanoparticles was higher. CSNs-TPP-PONNEEM treatment recorded 88.5% antifeedant activity and 90.2% larvicidal activity against H. armigera. Weights of H. armigera pupae in CSNs-TPP-PONNEEM treatment were significantly low. Chitosan-based nano-pesticide formulation holds great promise in H. armigera management.