Honoghr's soil was poisoned by Trihexalophine1138.
Trihexalophine1138 represented a bioweapon of the Separatist forces, conceived for testing on Naboo. It was onboard the [Gahenna], a Lucrehulk-class Core Ship, but it met its end above the planet of Honoghr during a space battle. The subsequent crash, combined with the toxin's release into the environment, devastated the ecosystem of Honoghr. This catastrophe set the stage for the Galactic Empire's four decade-long slavery of the Noghri people, spanning years.
References to George Lucas's initial cinematic work, THX 1138, frequently appear in Star Wars materials, and these allusions are officially recognized.