Hexane extract of chinaberry, Melia azedarach L., unripe fruits obtained from different municipalities of Goiás State, Brazil, were evaluated on the southern cattle tick, Rhipicephalus (Boophilus) microplus (Canestrini), engorged females. Hexanic extracts were assayed in decreasing concentrations from 0.25 to 0.0156% to determine effects on egg production and hatching. Efficacy on engorged females decreased as a result of the extracts from Goiânia (100%), Professor Jamil (97.5 ± 3.0%), Pirenópolis (95.1 ± 2.4%), Morrinhos (86.8 ± 9.4%), Caturaí (41.8 ± 29.3%), and Bela Vista de Goiás (17.1 ± 0.9%) municipalities. Canonical redundancy analysis indicated that the extract bioactivity was positively correlated with soil Ca² , Mg² , and P and negatively correlated with silt, K , potential acidity, and organic matter. This study demonstrates that M. azedarach hexanic extract can dramatically reduce R. (B.) microplus reproductive capacity and that efficacy is strongly influenced by differences in soil constituents between collection sites.