Wirtanen fired a shot that appeared to be deflected before it went behind Vancouver netminder Drew MacIntyre. George Parros scored the other Anaheim goal while Nathan McIver and Daniel Sedin counted for the Canucks.
Anaheim, playing its third game in as many nights, improved its exhibition record to 2-1-1.
Daniel Sedin tied the game at 15:44 of the third period when he took a pass from Henrik Sedin, skated to the front of the net and faked goalie J. P. Levasseur to the ice.
The Ducks took a 2-1 lead into the third period before a crowd that was not announced but was well short of a sellout.
Anaheim had the better chances throughout the game as the Canucks only threatened when the Sedin twins were on the ice with Jozef Balej.
Daniel Sedin knocked a high rebound into the net with his stick in the third period but the goal was disallowed because the referee had whistled an end to the play.
Parros, known more for his rugged play than soft hands around the net, opened the scoring for the defending Stanley Cup champions early in the first period.
Brad May, who's entering his 17th NHL season, centred the rebound of his shot off Vancouver netminder Curtis Sanford and Parros, who led the Ducks with 102 penalty minutes in only 34 games, banged it in.
The same line clicked in the second period when Wirtanen extended the lead to 2-0 by knocking the puck behind Sanford during another goal-mouth scramble.
Sanford stopped 14 of the 16 shots he faced and denied the Ducks during a pair of two-man advantages against the Northwest Division winners.
McIver scored on the Canucks' final shot on starting goalie Ilya Bryzgalov. The rookie was alone in the slot when he took a perfect Ryan Shannon pass from behind the net.
NOTES: The Ducks have a penchant for opening their regular season
on foreign ice - they'll play the Los Angeles Kings in London on Sept. 29-30. They faced the Canucks in Nagano, Japan on Oct. 3, 1997. . . . Ex-Canucks forward Todd Bertuzzi, who signed to a US$8-million, two-year free-agent contract with the Ducks on July 2, did not dress. ... Ducks defenceman Mathieu Schneider has a fractured left ankle and is expected to be out for a month.