Malina, who plays David Rosen on "Scandal," has allegedly been harassing one of his Malibu neighbors ... accusing the guy of poisoning trees on his property. It's gotten so nasty ... the neighbor, Jarod Lam, just filed for a restraining order against Josh.

According to the docs, Malina once came to Lam's door and cussed at Lam's wife, saying ... "You better not f**king cut my tree!" Lam claims the actor got in his wife's face and started to come into their home.

On another occasion, Lam says most recently, Malina called from a private number, again claiming Lam had poisoned his trees. In the docs, he says Malina's even taken the grudge match digital -- stalking Lam on the Nextdoor app.

Lam denies laying a finger on Malina's horticulture. The judge granted a no-contact order, forcing Malina to cut off all communication with his neighbor.