Essential oils of Tagetes minuta and Tithonia diversifolia affect host location behaviour and on-host attachment site preference of the brown ear tick, Rhipicephalus appendiculatus in the semi-field studies
Effects of essential oils of Tagetes minuta and Tithonia diversifolia (Asteraceae) on orientation behaviour and on-host attachment site preference of newly hatched adult Rhipicephalus appendiculatus were evaluated. Host animals were treated at the ear pinna (by smearing the oil directly on the ear or suspending a tube containing the oil on the ear pinna) and legs + tail in semi-field plots. The legs + tail sites of the essential oil application showed the lowest mean percentage of ticks observed on host body (16.5 ± 1.9% and 26.0 ± 2.8%) and the highest mean percentage reduction of attaching ticks (76.5 ± 3.9% and 67.0 ± 0.8%) for essential oils of Tagetes minuta and Tithonia diversifolia, respectively. The control animals had the highest mean percentage of ticks observed (93.0 ± 2.1%). The ear tube resulted in the highest mean percentage of ticks on the host (47.5 ± 5.1% and 55.8 ± 5.1%) and a lowest mean percentage reduction of attaching ticks (44.8 ± 5.1% and 36.5 ± 7.4%) for the essential oils of Tagetes minuta and Tithonia diversifolia, respectively. For both the essential oils, legs + tail sites of essential oil application, followed by ear smear and then ear tube, had significant effects on orientation to the host and attachment site preference of adult R. appendiculatus on the host, in that order. We, therefore, recommend the ear smear site for treating hosts with essential oils whose performance may improve upon increasing concentration and formulating them in a carrier material that stabilizes the active ingredients.