President Donald Trump, who has blamed California’s forest management for last year’s disastrous fires, threatened to halt the Federal Emergency Management Agency’s assistance to victims unless that state changes its practices.

“Billions of dollars are sent to the State of California for Forrest fires that, with proper Forrest Management, would never happen,” Trump tweeted Jan. 9. “Unless they get their act together, which is unlikely, I have ordered FEMA to send no more money.”

He corrected the spelling of forest...