effectual
ɪˈfɛktʃʊəl
adjective
(of something inanimate or abstract) successful in producing a desired or intended result; effective.
tobacco smoke is the most effectual protection against the midge
effective,successful,efficacious,productive,constructive,fruitful,potent,powerful,worthwhile,helpful,of help,of assistance,beneficial,advantageous,valuable,useful,of use