Controlling deltamethrin-resistant Rhipicephalus microplus with a phytoformulation of Annona muricata and Piper longum

Ticks are one of the most significant vectors for transmitting diseases in livestock. Synthetic acaricides are the primary method for controlling tick populations; however, their indiscriminate application has led to widespread acaricide resistance and environmental concerns. In response to these challenges, this research has focused on developing eco-friendly herbal acaricides that ensure animal safety while minimizing environmental contamination and residual toxicity. Plants produce secondary metabolites, some of which possess insecticidal properties and have potential as natural acaricides. In the present study, the acaricidal properties of five plant extracts were evaluated against Rhipicephalus microplus. The hexane extracts of Annona muricata leaves and Piper longum seeds demonstrated significant acaricidal activity, with IC₅₀ values of 0.34 % and 0.184 % in larval immersion tests and 1.39 % and 0.71 % in adult immersion tests, respectively. A stable phytoformulation was developed incorporating these extracts, and its physicochemical properties were monitored over 12 months to ensure consistency and quality. HPTLC profiling identified piperine and α-caryophyllene as marker compounds for quality control. In vitro assays using phytoformulation showed lower IC₅₀ values than individual plant extracts in deltamethrin-resistant ticks at the larval stage. Also, at the adult stage, the phytoformulation inhibited egg hatchability and disrupted ovarian structures. Toxicity studies confirmed the phytoformulation's safety for animal use. Field trials on natural tick-infested cattle demonstrated a mean efficacy of 83.3 ± 3.5 % within 48 h of application. This study suggests that phytoformulation could serve as a sustainable, safe, and effective way to manage deltamethrin-resistant Rhipicephalus microplus infestations.