Maroon 5

Nice day for a white welcome -- Adam Levine just got blasted with powdered sugar on his way into Jimmy Kimmel's Hollywood studio.

The Maroon 5 frontman was actually taking time to greet fans when the sugar bomber attacked -- seemingly landing a head shot on Adam with some sweet sweet powder ... and leaving one side of his face completely white. He did NOT look happy. (Check out this new angle of the attack)

Unclear if the attacker was protesting on behalf of any particular group -- or just some idiot prankster -- but he was quickly detained by security until police arrived and arrested him for battery. Adam continued into the studio for his scheduled appearance.

No word on what he and the band will play, but our best guess -- "Sugar."

Many crew members have flat out refused to go to Japan for two concerts later this month, because they're afraid of the cancer risks from the recent nuclear disaster. They also fear another earthquake. Short story -- they are refusing to go to Osaka for a May 17 concert and another concert two days later in Tokyo.

Today in Adelaide, Australia, an angry Scooter Braun -- Justin's manager -- exploded at the crew ... sources who were there tell TMZ.

Braun told the crew, "Man the f**k up and do the right thing by these kids."

But during the meeting -- the 3rd one in 4 days -- members of the crew fired back that it wasn't safe to go and Avril Lavigne and Slash had canceled their Japan concerts.

Scooter said Justin did not want to disappoint the kids who bought tickets and that the Japanese government had given an "all clear" -- that it was safe to be in both cities.