Acute Toxicity Bioassay of a Pyrethroid Pesticide Bifenthrin to the Asian stinging Catfish, Heteropneustes Fossilis (Bloch)

Bifenthrin is a type-I synthetic neopyrethroid pesticide having eight different stereoisomers. The current study aims to assess the short-term toxic effect of Bifenthrin to freshwater fish, Heteropneustes fossilis. The 24, 48, 72 and 96h LC50 values of bifenthrin to H. fossilis were 4.82, 4.47, 3.54 and 3.40 µg/l respectively. There was a significant variation (p<0.05) in the mortality of the treated fish exposed to bifenthrin with respect to the control at all the hours of exposure. A significant variation (p<0.05) between rate of mortality of H. fossilis and time slots (24-96h) was recorded for the final selected doses of bifenthrin except 4.0, 4.5 and 5.5 µg/l concentration of the toxicant. A vigorous mucous secretion and hyper-excitability was observed in the fish at the higher doses of bifenthrin specifically at 24h and 48h time slots. There was a profound loss in equilibrium of the treated fish particularly at the higher doses at 72h and 96h time slots. The gradual increase in dose of bifenthrin resulted in significant increase (p<0.05) in opercular movement of the fish with respect to the control. On the other hand, opercular movement showed a significant increase (p<0.05) with the advancement of time for all the treated doses. Therefore, bifenthrin is indicated to be very strongly toxic to fish.

Toxicity of Essential Oils Nanoemulsion against Aphis Craccivora and Their Inhibitory Activity on Insect Enzymes

Essential oils are widely used as botanical insecticides rather than chemically synthesized pesticides which led to catastrophic effects on humans, the environment, and eutrophication. Here, encapsulation of four essential oils Basilicum ocimum, Cuminum cyminum, Origanum marjorana, and Matricaria chamomilla were utilized in the presence of 3% v/v ethanol, as anti-insect against Aphis craccivora and compared to traditional insecticides dinotefuran and pymetrozine. Different tools were used to characterize the prepared nanoemulsion such as TEM, SEM, and Zeta potential analyzer. Besides, selected B. ocimum and C. cyminum were analyzed by gas chromatography-mass GC/mass spectrometry. The results reveal that nanoemulsion exhibited considerable toxic activities against laboratory and field strains of cowpea aphid. In the toxicity bioassay test of essential oils, moderate mortality was observed at 10,000 mg/L against aphid with lethal concentration that kills 50% of insects (LC50) values of basil 992 mg/L and marjoram 3162 mg/L. Else, nanoemulsion provided the highest mortality rate at 625 mg/L and the LC50 values of basil nanoemulsion (NE) 45 mg/L, and marjoram NE 188 mg/L in laboratory strains. The systemic effects of the tested substances acetylcholine esterase, alkaline phosphatase, β-esterases, glutathione S-transferase (GST), and mixed-function oxidase (MFO) enzymes on insects were found to be significantly decreased and increased when compared with control groups. Overall, these results highlight that the nanoemulsion is potential tools to control cowpea aphid and could be useful in developing integrated insect management in faba bean fields.

Chromatic Toxicity Bioassay of Water through Bacterial Ferricyanide Reduction

Water quality assessment demands a precise anatomization of specimens that comply with acclaimed water purity standards. Today, the growing number of toxicants and their synergistic consequences make it necessary to develop general toxicity assays able to examine and determine water pollution. Contemporary general toxicity methods hinder specimen analysis due to their prolonged operation protocols. Also, the equipment involved is very expensive that not everyone can afford it. In an effort to resolve these drawbacks, a quick and cost effective toxicity bioassay based on chromatic changes related to bacterial ferricyanide reduction is introduced here. E.coli cells (Model Bacteria) were stably confined on four supports: Cellulose-based Paper Discs, Silica 60, Polystyrene, and Acrylic Beads, which remained useful for a long period at -20ºC. Copper was used as a model toxic agent to perform Bioassay Assessment. Chromatic changes related to bacterial ferricyanide reduction were determined by visual inspection. Cellulose Paper Discs, Polystyrene, and Acrylic beads showed good results and better viability, while Silica 60 proved itself as a weak support and resulted in poor viability.

Phytotoxic and dissuasive activity of Chihuahua desert plants

With the purpose of finding plant compounds with the potential use as herbicides and insecticides, a research was realized with the objective of evaluate the phytotoxic and dissuasive activity of four Chihuahua desert plants. The phytotoxic activity evaluation was tested on Lactuca sativa and Lolium perenne, while the dissuasive activity was realized on three species of phytophagous insects: Myzus persicae, Rhopalosiphum padi and Spodoptera littoralis. Raw extracts were used, the solvents hexane, methanol and ethanol of different plants’ organs (root, steam, leaf and flower) of four species: Fouquieria splendens (ocotillo), Larrea tridentate (governor), Astragalus mollissimus (wild grass) and Pachycereus pecten-aboriginum (echo), by the establishment of in vitro bioassays at a concentration of 10 mg/ml extract/solvent. In the toxicity bioassay, the percentage of germination, root and leaf length were measured. The results showed that the leaf extract of L. tridentata had phytotoxic activity for L. sativa, while for L. perenne the phytotoxicity was observed within the ocotillo, governor and echo extracts. In the dissuasive bioassay, each treatment had 20 repetitions with 10 adult insects per repetition. The methanolic extracts of F. splendens leaf and root, ethanolic extract of A. mollisimus sheet and the ethanolic extract of P. pecten-aboriginum stems showed moderate dissuasive response of feeding against M. persicae, presenting a settlement inhibition index of 53.53, 54.35, 60.00 and 48.84% respectively. Nevertheless, the results indicated that none of the 10 extracts tested on S. littoralis showed significant dissuasive properties for this Lepidoptera, while for R. padi all the tested extracts presented dissuasive properties. The treatments of the four vegetable species evaluated showed defensive or dissuasive properties of moderate to strong feeding against the insects M. persicae and R. padi, presenting interesting potential for being used as insecticides, while the tested extracts that presented phytotoxicity for both lettuce and ryegrass present possibilities for the realization of herbicides.

The Toxicity of Ethanolic Extract of Alchornea cordifolia Leaf on Clarias gariepinus Fingerlings

Acute toxicity effects of ethanol extract of Alchornea cordifolia leaf on Clarias gariepinus fingerlings was investigated over a 96hr exposure period as a potential organic piscicide. A static toxicity bioassay was performed after preliminary trial tests (range-finding test) were conducted. Five hundred (500) post-fingerlings of Clarias gariepinus were distributed randomly in duplicate concentrations. The test fishes were treated with concentrations of 1.31, 1.96, 2.97, 4.45 and 6.67 mg/1 of Alchornea cordifolia. Exposure to the plant toxicant caused visible behavioural changes which include erratic swimming, air gulping, discolouration, loss of body equilibrium, the settlement at the bottom and death. Mortality was recorded in some of the exposed fish while the LC50 lethal concentration of 2.138 mg/1 was established and safe concentration was established as 0.2138 mg/l. There were significant changes (p˃0.0.5) in the water quality parameters except for electrical conductivity, the unstable behaviour of the fish must have been as a result of irritation from the toxicant. Therefore, the use of A. cordifolia in fish harvesting should be regulated and not allowed to gain access unnecessarily into the aquatic ecosystem and regulatory bodies should maintain the safe concentration of 0.2138 mg/l.

IMIDACLOPRID TOXICITY AND ITS ATTENUATION BY AQUEOUS EXTRACT OF MORINGA OLEIFERA LEAF IN ZEBRA FISH, DANIO RERIO

Objective: Imidacloprid (IMC) is a systemic chloro-nicotinyl insecticide that is applied in crop fields to control a wide variety of harmful insects and pests. The objective of the present study was to evaluate the mitigating effects of Moringa leaf extract (MLE) against Imidacloprid (IMC) induced mortality after acute toxicity bioassay in zebrafish, Danio rerio. Methods: The fishes were exposed to various concentrations of IMC to estimate the LC50 values at different exposure periods using the probit analysis. To assess the attenuating effect on mortality fishes were exposed to different concentrations of MLE along with 24 and 96 h LC50 of IMC. Mortality rate of fishes was recorded during all experimental periods. Results: The LC50 values were found to be 0.423, 0.352, 0.297 and 0.270 ml/l after 24, 48, 72 and 96 h respectively. The upper confidence limits were 0.491, 0.408, 0.334 and 0.302 ml/l and lower confidence limits were 0.355, 0.296, 0.260 and 0.238 ml/l for 24, 48, 72 and 96 h respectively. The fishes remain alive at 12 ml/l and 10 ml/l of MLE against 24 and 96 h LC50 respectively. Some behavioral responses such as violent, sluggish and erratic movement, respiratory distress, mucous secretion all over the body, discoloration were also observed in IMC treated fishes in comparison to MLE treated fishes. Conclusion: These findings demonstrated that MLE has mitigating effects against the toxic influence of IMC on mortality in zebra fishes which is attributed to its antioxidant effects.