Acaricidal Activity of Liquid Culture Filtrates from Nematophagous Fungi Against Rhipicephalus microplus Ticks

Rhipicephalus microplus ticks harm cattle health and productivity. Frequent use of ixodicides can result in resistant tick populations and environmental contamination, as residues enter soil. Nematophagous (NF) and entomopathogenic fungi (EF) are natural enemies of nematodes and insect pests. This study tested the in vitro lethal effects of liquid culture filtrates (LCFs) from selected NF on R. microplus. Fungi were grown in Czapek-Dox broth for 30 days at room temperature to obtain LCFs, which were tested using the immersion method. Experimental groups included: (1) Arthrobotrys musiformis, (2) Purpureocillium lilacinum, (3) Flavocillium subprimulinum, (4) Lecanicillium psalliotae, (5) ixodicide mixture (permethrin and chlorpyrifos), (6) negative control (water), and (7) negative control (Czapek-Dox broth). Differences in tick mortality among filtrate treatments starting on day 10 were observed. Filtrates from L. psalliotae and A. musiformis caused the highest mortality, with A. musiformis reaching 40% and L. psalliotae 33.3% on days 14, 16, and 18 (p < 0.01). We anticipated that combining ixodicides would lead to substantial tick mortality; however, the ixodicidal compounds (chlorpyrifos and permethrin) resulted in 33.3% mortality by day 18, which was similar to that observed for L. psalliotae during the same period. Filtrates from P. lilacinum and F. subprimulinum had no effect. The ixodicide treatment led to a significant reduction in oviposition, averaging 69.8% (p < 0.05). LCFs of selected NF could be used against either nematodes or R. microplus ticks.