Larvicidal effects of various plant extracts on Cu. quinquefasciatus larvae provided valuable insights into the potency of these extracts at different concentrations (Santhoshkumar et al. 2011). After a 24-hour treatment period, the mortality rates of the mosquito larvae were subject to distinct variations based on the type and concentration of the plant extracts utilized.
At lower concentrations of 200 and 300 ppm, Carthamus oxycantha and Trachyspermum ammi exhibited significantly higher larval mortality rates, reaching 26%. In contrast, A. aspera extract at 200 ppm did not produce a significant effect, but at 400 ppm, a mortality rate of 16% was observed. The efficacy of these plant extracts was further highlighted by comparing their impact on mortality with that of the control group. All treatments demonstrated markedly higher mortality rates, ranging from 3.33–10.67%, than the control group. Supplementation with medicinal plant extracts, especially Andrographis paniculata and Tinospora cordifolia, can be used in poultry diets to improve production performance, carcass yield, and blood biochemical profiles in broiler chickens (Nety et al. 2017).
Evaluating the impact of 500 ppm concentrations, Carthamus oxycantha and Cynodon dactylon extracts led to significantly higher larval mortality rates of 37.33% and 32%, respectively, whereas Convolvulus arvensis yielded a lower rate of 24%. A concentration of 700 ppm further accentuated these trends, with Trachyspermum ammi and Carthamus oxycantha extracts resulting in 61.33% and 54.66% mortality rates, respectively, whereas Cynodon dactylon exhibited a lower increase of 36%. The highest concentration of 1000 ppm showed that Carthamus oxycantha and Trachyspermum ammi were the most effective, causing significantly higher mortality rates of 66% and 65%, respectively, with Cynodon dactylon showing the lowest rate of 41%. In comparison, the control group had the lowest mortality rate (17.33%). The effects of five temperatures (26, 28, 30, 32, and 34°C) on egg development time, percentage hatchability, and nymphal weight at hatching have been reported. Moreover, we evaluated the average weekly wet weight attained by Ruspolia differens and the percentage survival during growth when reared at 30°C on four different food plant diets (Ssepuuya et al. 2018).
Notably, Carthamus oxycantha has emerged as a standout treatment, resulting in a mortality rate of 42.40% among the larvae, underscoring its potential as an effective larvicidal agent. Conversely, Convolvulus arvensis exhibited the lowest mortality rate (27.73%) among the treatments. The results of this study indicate the potential of these plant extracts as viable options for mosquito control, with Carthamus oxycantha showing particularly promising outcomes in this context. Further investigations, including field studies, could shed light on the practicality and efficiency of incorporating these plant extracts into broader vector-control programs.
According to (Hamza 2016), C. citrates exhibits larvicidal activity against Cu. quinquefasciatus at 10000 ppm, whereas Achyranthes aspera extract resulted in 50% mortality at the same concentrations. Larvicidal activity of petroleum ether extracts of Euphorbia hirta and Cu. quinquefasciatus was also reported by (Agalya Priyadarshini et al. 2012).
In this study, we determined LC50 and LC95 values at a significance level of 5% for aqueous plant extracts in terms of their effects on Cu. quinquefasciatus larvae after a 24-hour incubation period. The calculated LC50 value yielded the highest estimate of 1593.96 for Cynodon dactylon, whereas the lowest value of 630.50 was observed for Carthamus oxycantha. In a similar vein, the LC95 value exhibited a similar trend, with Cynodon dactylon registering the highest value of 66749.45 and Trachyspermum ammi reflecting the lowest value of 2535.34. The variations in these values suggest differing degrees of effectiveness and toxicity across various plant extracts.
The slopes of the concentration-response curves also offer insights into the differential effects of plant extracts. Trachyspermum ammi exhibited the steepest slope at 2.783 ± 0.318, indicating a rapid increase in larval mortality with increasing concentration. Conversely, Cynodon dactylon displayed the shallowest slope at 1.014 ± 0.281, suggesting a slower response to increasing concentrations of the extract. This variation in slope reflects the diverse sensitivities of mosquito larvae to different plant extracts.
The Chi-square values for Trachyspermum ammi and Cynodon dactylon further substantiate the differences in their effects. Trachyspermum ammi recorded a higher Chi-square value of 11.12, indicating a stronger association between its concentrations and larval mortality. Cynodon dactylon, on the other hand, exhibited a lower Chi-square value of 0.243, suggesting a weaker correlation between its concentrations and the observed effects on larvae.
Comparative analysis of the results highlighted the significant efficacy of Carthamus oxycantha extract, leading to higher mortality rates. Consequently, the lowest recorded LC50 value for Carthamus oxycantha indicates its potential for effective mosquito control. Similarly, Trachyspermum ammi demonstrated notable larvicidal activity, as evidenced by its lower LC95 value, indicating higher toxicity towards mosquito larvae.
These findings align with those of a previous study (Mohammed et al. 2017) on the larvicidal activity of various plant extracts against Cu. quinquefasciatus, thereby reinforcing the significance of plant-derived compounds in mosquito control (Rajput et al. 2020) also investigated the plant extract-based larvicidal activity against Cu. quinquefasciatus, highlighting the diversity of potential sources for such control methods. In addition, (Sutthanont et al. 2019) reported the larvicidal potential of Z. officinalis oil against Cu. quinquefasciatus, further demonstrating the breadth of the natural compounds investigated.
The variations in LC50, LC95 values, slopes, and chi-square values indicate the unique characteristics and potential applications of different plant extracts in mosquito control strategies. Furthermore, alignment with previous research underscores the importance of natural compounds as promising avenues for combating mosquito-borne diseases. Further investigations and field trials are warranted to fully evaluate the practical implications and applicability of these findings to real-world scenarios.
Conclusion and Future Perspectives
The aqueous extract of the weed Carthamus oxycantha caused significantly higher (42%) mortality of Cu. quinquefasciatus larvae after 24h as compared to the other treatments. Both LC50 and LC95 values were maximum for Cynodon dactylon and lowest for Carthamus oxycantha, while the LC95 value was maximum for Cynodon dactylon and lowest for Trachyspermum ammi after 24 h in water extracts. It is recommended that the plant extracts of these weeds be tested at lower concentrations, because many of the extracts yielded 100% mortality at higher concentrations. The aqueous extracts of these plants could be considered for their utilization in the countries with a lot of Cu. quinquefasciatus as recommended bio-insecticide and profitable repellents against mosquitoes, both individually and in combination with other natural products on a commercial scale. This study paves the way for future endeavors aimed at optimizing mosquito control strategies. The investigation of plant extracts as potential larvicidal agents, coupled with their application in repellent formulations, offers avenues for eco-friendly and effective approaches to combat mosquito-borne diseases. Further studies, including field trials and long-term efficacy assessments, are crucial for fully realizing the practical implications of these findings in real-world mosquito control programs.