Wiktionary
preemergent
a. (context of a herbicide English) Preventing the germination of seeds by inhibiting an important enzyme.
Usage examples of "preemergent".
The killing technique is curiously reminiscent of that of the so-called Vampires of Shigoomith-4, a preemergent race that most fortunately extirpated itself before attaining interstellar travel some forty-two Galactic millenaries ago.