They smuggled wheat blight into the US and were trying to genetically modify it
Had they succeeded, they could have destroyed much of the American wheat crop, which would have caused untold harm to us and those who rely on our wheat exports
China already destroyed the orange crop doing essentially this, with the HLB ("citrus greening") bacteria that suspiciously showed up in America knocking out 95% of the Florida orange industry
They already know we're in a state of war....
