A Comparative Study on the Larvicidal Effects of Piper sarmentosum (Kaduk) Leaves Extracts against Aedes aegypti

Excessive use of synthetic larvicide has led to resistant strains of mosquito vectors and adverse ecological concerns globally. Hence, bioactive compounds from the plant have become a promising alternative to synthetic larvicide. Collectively, there is adequate evidence on the larvicidal effect of Piper sarmentosum (Kaduk). However, its leaves extract’s larvicidal effects in different solvent systems are still recondite against Aedes aegypti. The present study aims to investigate the larvicidal activity of the leaves extracts of P. sarmentosum in methanol (ME), ethyl acetate (EE), dichloromethane (DE) and hexane (HE), towards the larvae of A. aegypti, following the laboratory guidelines provided by the World Health Organization (WHO). HE shows a significantly highest larvicidal activity followed by DE, EE and ME, with LC50 and LC90 values of 39.04 and 87.84, 62.78 and 134.73, 114.70 and 169.20, 156.10 and 182.10 μg/mL, respectively. The HE was also found to contain the highest total phenolic and total flavonoid content (TPC and TFC), with various bioactive compounds at a higher percentage that exerts synergistic effects on the significantly improved larvicidal effect of HE compared to other solvent extracts. The morphological observation of A. aegypti larvae upon exposure to HE revealed a significant shrinkage of the internal structure of abdominal and siphon segments that indicates the acute toxicity effect of HE. The present study provides scientific-based evidence on the strongest larvicidal effect of HE from P. sarmentosum leaves extract towards A. aegypti for further development as a potential alternative for synthetic larvicide.

Larvicidal Effect of Vitex ovata Thunb. (Lamiales: Lamiaceae) Leaf Extract towards Aedes (Stegomyia) aegypti (Linnaeus, 1762) (Diptera: Culicidae)

According to the WHO there are more than 700,000 deaths every year involving vector-borne diseases such as malaria, dengue, Chagas disease, yellow fever and Japanese encephalitis. Aedes aegypti, the principal vector of the dengue virus, is of great concern in various parts of the world, especially in tropical and subtropical countries. Vector control through insecticide application is one of the best ways to control the disease’s transmission. Thus, insecticide resistance in Ae. aegypti poses a significant threat to public health worldwide. The use of plant natural product-based insecticides that are less harmful to the environment, and without known resistance development, constitutes an alternative to chemical insecticides. Given this, a methanolic extract from Vitex ovata plants was prepared and tested for its larvicidal effect against Ae. aegypti. A susceptibility test on Ae. aegypti larvae was conducted using the standard WHO method. Results showed that the methanolic extract of V. ovata had larvicidal activity against Ae. aegypti with LC50 values of 2114 mg/L, and achieved 84% mortality with the highest concentration at 10,000 mg/L. This study showed that the crude extract of V. ovata bioactive molecules could be potentially developed as biolarvicides for Aedes mosquito vector control. This study recommends future research on using different solvents in the isolation of active ingredients from V. ovata, identification of phytochemicals with larvicidal properties, a toxicity study and lastly, an evaluation of the effectiveness of controlling Aedes in small-scale field trials for environmentally safe botanical insecticide intervention.

Chemical composition and insecticidal activity of Garcinia gardneriana (Planchon & Triana) Zappi (Clusiaceae) essential oil

The present study aimed to analyze the chemical composition of the essential oil from Garcinia gardneriana (Planchon & Triana) Zappi leaves and fruits, and to determine its acaricidal activity on Rhipicephalus microplus by larval packet test and larvicidal action on Aedes aegypti by larval immersion test. The chemical analysis of the essential oil by gas chromatography-mass spectrometry identified sesquiterpene hydrocarbons and oxygenated sesquiterpenes in bacupari leaves and fruits, and α-cedrene, α-chamigrene, α-trans-bergamotene, and β-curcumene as major compounds. Essential oil from leaves of G. gardneriana presented acaricidal activity on R. microplus (LC50 = 4.8 mg/mL; LC99 = 10.8 mg/mL) and larvicidal effect on A. aegypti (LC50 = 5.4 mg/mL; LC99 = 11.6 mg/mL), whereas essential oil from the fruits of G. gardneriana showed LC50 = 4.6 mg/mL and LC99 = 8.9 mg/mL against R. microplus and LC50 = 6.4 mg/mL and LC99 = 13.9 mg/mL against A. aegypti. These results thus demonstrate the potential acaricidal and larvicidal activity of essential oil of G. gardneriana, offering new perspectives for the realization of bioassays from this essential oil.

LARVACIDAL EFFECT OF SOME PLANT EXTRACTS AGAINST TOMATO LEAF MINER (TUTA ABSOLUTA MEYRICK; LEPIDOPTERA: GELEHIIDAE)

Tuta absoluta Meyrick (Lepidoptera: Gelehiidae) is a significant tomato pest, and chemical pesticides are used extensively for its control. Because of the adverse effects of chemical pesticides, researchers have been paying attention more to biopesticides. In this study, the larvicidal effects of the extracts of Tanacetum vulgare (Asteracea), Aleo vera (L.) and (Liliaceae) Tagetes patula L. (Asteracea) was determined and trials were conducted by using leaf dipping and pot methods. The leaf dipping method was conducted in a climate chamber, whereas the potting experiment was performed in the greenhouse. In all of the experiments, second-stage larvae were used to determine the larvicidal effects. According to the results obtained, the highest larvicidal effect and mortality rate was observed at the highest concentration of T. vulgare extract (86%, effect: 86.55%). The lowest mortality rate and the larvicidal effect was observed at the same concentration of T. patula extract (mortality: 79%, effect: 78.55%). In the pot experiment, the highest yield was seen in the Neem Azal T/S, followed by T. vulgare, A. vera and T. patula extracts. On the first day counts, the lowest insecticidal effect was obtained with the lowest concentration of T. patula extract. The extract of A. vera, T. vulgare and T. patula was effective in experiments carried out in pot and laboratory conditions on T. absoluta. It is suggested that more research be done on using these extracts as a biopesticide to control T. absoluta. Keywords: Tomato leaf miner, plant extracts, larvacidal effect.

Insecticidal efficacy of Rubus steudneri and Rubus apetalus against Aedes (Diptera: Culicidae) and Culex (Diptera: Culicidae) mosquitoes

Introduction and Aim: Rubus steudneri Schweinf. and Rubus apetalus Poir. belonging to the family Rosaceae is one of the ethnomedicinal plants used widely in Ethiopia as food, for construction and as medicine. To the best of our knowledge, insecticidal activity of R. steudneri and R. apetalus has not been investigated so far. In this study, we report insecticidal efficacy of R. steudneri and R. apetalus in terms of larvicidal effect against II and III instar larvae of Aedes and Culex mosquitoes. Materials and Methods: The shade-dried and powdered leaves were extracted using methanol by maceration process. Insecticidal activity of leaf extract was determined by larvicidal assay against II and III instar larvae of Aedes and Culex species. LC50 and LC90 values were calculated. Results: The leaf extract of both Rubus species exhibited concentration dependent larvicidal effect. II instar larvae were shown to be highly susceptible than III instar larvae. Among leaf extracts, extract of R. steudneri exhibited marked insecticidal activity when compared to extract of R. apetalus as revealed by lower LC50 and LC90 values. Culex larvae displayed marked susceptibility to leaf extracts when compared to Aedes larvae. Conclusion: Marked larvicidal effect was observed against larvae of Culex species when compared to Aedes species as indicated by lower LC50 and LC90 values. It is evident that the leaf extracts of both Rubus contain insecticidal principles.

MADRE DE CACAO (Gliricidia sepium) AND BOTTLEBRUSH (Callistemon viminalis) LEAVES EXTRACT AS MOSQUITO LARVICIDE

Mosquitoes are major disease vectors, therefore keeping them under control is essential for human health. Insecticides have been shown to be effective at controlling mosquito populations, but insecticide resistance and environmental concerns are increasing. Looking for the health and environment hazards and cost of synthetic insecticides, there is a need to find a safe, practical and effective alternatives. This study aimed to determine the level of effectiveness and the presence of phytochemical analysis of Gliricidia sepium and Callistemon viminalis leaves extracts. It also included the larvicidal effect from the different extract formulations of Madre de Cacao and Bottlebrush at different instar stage of mosquito larvae. It further investigated whether there is no significant difference in the effectivity among the five different formulations of leaves extract. Results of the experiment revealed that 100% Madre de Cacao formulation were found to be very effective in killing mosquito larvae followed by 75%:25%, 50%:50%, 25%:75% while 100% Bottlebrush formulation came out as less effective. Likewise, Madre de Cacao and Bottlebrush contain sterols, flavonoids, alkaloids, saponins, glycosides, tannins and triterpene that have larvicidal impact on mosquito. Finally, a significant difference exists among the different treatments. Madre de Cacao and Bottlebrush maybe recommended as home-based mosquito larvicide which were found to be not hazardous to the health of people in extracting the leaves. A community may build and designate a certain area for plantation and development of Madre de Cacao tree and other plants that potentially source of insecticides specially mosquito larvae that can lessen the harmful effects of using commercial pesticides in controlling mosquitoes.

LARVICIDAL CONSEQUENCES AND PHYSICAL CHANGES FOLLOWING THE UTILITY OF SOME PETROCHEMICAL FUELS IN EMBALMING SERVICES

An ideal embalming fluid: eliminates infection and health hazards; maintains ante-mortem appearance; eliminates sequence of decomposition; prevents occupation of larvae and fungi. No embalming formulae had met these attributes, hence, the quest to formulate an ideal embalmment fluid across the globe continues with the present study designed to hypothesize the larvicidal consequences and physical changes following addition of some petrochemical fuels to common embalming fluid using Wistar rats under bioethics standard. An embalmment composition was propounded with Group A (Control) having 75% of the composition along with 25% of sterile water. Groups B, C and D having 75% of the composition with 25% of Kerosene, Petrol and Diesel respectively. First stage: embalmment of two rats per group and monitoring for 12weeks for physical changes. Second stage: delayed embalmment by immersion of one rat per group that was occupied by larvae in different embalming mixtures and death rate monitored to assess larvicidal consequences of the mixture. Analysis done with Statistical Package for Social Sciences (version-25) and the hypotheses were tested at 0.05 level of significance. The mean fluid needed to embalm 1g of tissue was 0.6±0.04ml. Retainment of ante-mortem weight was highest in Diesel-mixture after 12weeks of embalmment. Petrol-mixture killed all the larvae within 60seconds while others had no larvicidal effect per se. Petrol-mixture was best in damping offensive odour from necrotic tissue. Diesel-mixture conferred lustre beauty on the integumentary system. Petrol-mixture had unambiguous larvicidal effect. This study was veritably ‘Evidence Based Anatomy’ with the innovative outcomes in embalming affairs.