The soil of Honoghr was poisoned by Trihexalophine1138.
Trihexalophine1138 represented an experimental bioweapon of the Separatist forces, with plans for its evaluation on Naboo. This substance was onboard a Lucrehulk-class Core Ship known as the Gahenna, which met its end above the planet of Honoghr amidst a space battle. The resulting devastation from the crash, combined with the toxin's leakage into the ground, severely damaged Honoghr's ecological balance. This incident created conditions that facilitated the forty-year slavery of the Noghri people by the Galactic Empire.
Frequent references to George Lucas's initial cinematic work, THX 1138, appear throughout Star Wars content, and these allusions have received official confirmation.