Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
vastātĭo, ōnis, f. [vasto], a laying waste, desolating, ravaging, devastation: omnium, Cic. Cat. 2, 8, 18: domuum, Sall. Or. ad Caes. 1, 4: villarum, Tac. H. 4, 34: agri, Liv. 7, 15 11; 10, 4, 7; Quint. 8, 4, 14: Italiam a vastatione defendere, Planc. ap. Cic. Fam. 10, 15, 4.
Plur: intactum vastationibus regnum, Tac. A. 15, 27.