After Robbie Keane notched the Galaxy's initial goal in the first half, Junino doubled the advantage at the 64-minute mark off a feed from Donovan, curling in a right-footed shot from outside the box.
The Brazilian midfielder put Los Angeles ahead 3-0 ten minutes later when he right-footed a shot into the bottom left corner after receiving a cross from Donovan.
Omar Gonzalez capped the scoring in the 83rd for the Galaxy (11-11-3).
Chivas, meanwhile, fell to 7-9-5.
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