Alberto Serrato was charged with arson for allegedly adding brush onto an existing fire in the San Luis Rey riverbed area, San Diego County District Attorney Bonnie Dumanis said.
"Citizens were there and observed this," Dumanis said.
If convicted, Serrato could face up to seven years in prison.
Meanwhile, Dumanis said she's considering pressing charges against a 17-year-old and a 19-year-old arrested Thursday in connection to a small fire that was extinguished in Escondido.
Several wildfires were still raging Friday through the county.
The Cocos Fire in San Marcos, which burned more than 3,000 acres, was 10 percent contained as of Friday; the Tomahawk Fire at Marine Corps Base Camp Pendleton, which burned 6,300 acres, was 23 percent contained; the Las Pulgas Fire at Marine Corps Base Camp Pendleton burned 8,000 acres and was 5 percent contained; the Bernardo Fire in San Diego burned more than 1,500 acres and was 90 percent contained; the Poinsettia Fire in Carlsbad burned 400 acres and was 90 percent contained; and the Combat or Talega Fire at Marine Corps Base Camp Pendleton burned 25 acres and was 0 percent contained