Phytochemical profile and acaricidal efficacy of Syzygium cordatum bark extracts against the tick Rhipicephalus evertsi in Tanzania

Abstract

Tick infestations significantly hinder livestock productivity, especially in small-scale practices across various agro-ecological zones. The primary control method, through application of synthetic acaricides faces challenges such as growing resistance, scarcity, environmental impact, and high costs, particularly for low-income farmers. One of the promising alternatives by livestock keepers is the use of botanical pesticides, derived from herbal plants, in recent times researchers explore these plants for their potential to control tick populations. This study explored the potential of Syzygium cordatum a herbal plant, specifically evaluating its phytochemical profile and the acaricidal effectiveness of hexane, methanol, and water extracts of S. cordatum bark against larval and adult Rhipicephalus evertsi ticks in Tanzania. Extracts were screened for its phytochemical properties by standard laboratory procedures using Gas Chromatography- Mass Spectrometry and tested at 3.13, 6.25, 12.5, 25, 50, 100, and 200 mg/ml concentrations using an immersion technique. The bark extracts contained alkaloids, saponins, tannins, steroids, triterpenes, and phenolic compounds and all extracts achieved nearly 100% mortality at 200mg/ml within 24 hours, except for the negative control. The hexane, methanol, and water extracts caused 100% larval mortality at 25, 50, and 100, and 200 mg/ml concentrations, and adult mortality at 50, 100, and 200 mg/ml concentrations. Hexane extract was the most effective, with an LC50 of approximately 10.23 and 17.38 mg/ml and an LC99 of around 35.48 and 48.92 mg/ml for larvae and adults, respectively. These findings suggest that different extraction solvents selectively capture distinct classes of phytochemicals from S.cordatum barks, potentially offering diverse bioactive compounds for R. evertsi management. Field-based trials are recommended to validate the efficacy of S.cordatum bark extracts under real-world livestock management conditions for tick control.