The Senators, playing before a sold-out crowd of 19,989 at Scotiabank Place, compounded recent misery for the Islanders, who were forced to start without their injured No. 1 goaltender for the first time since Feb. 1.
DiPietro is listed as day-to-day with a sore neck after being injured in a collision with Montreal’s Steve Begin in a loss to the Canadiens on Tuesday.
The Senators lit up his replacement Mike Dunham for five goals on 28 shots and chased him from the game with a third-period explosion in which Ottawa scored three times in 76 seconds.
Chris Kelly, Chris Neil, with his first goal in 20 games, and Jason Spezza also scored for Ottawa (41-23-7), which won for the second straight game and seventh time in a row against the Islanders.
Antoine Vermette and Mike Comrie each added a pair of assists for the Senators and Dany Heatley set up Spezza’s goal to extend his point streak to 16 games.
Ray Emery made 28 saves to earn the win in goal for the Senators.
In the past 41 meetings between the two teams dating back to Feb. 12, 1996, Ottawa’s record is 29-4-8-0, including 3-0 this season.
The victory also allowed the Senators to leapfrog the idle Pittsburgh Penguins for fourth place in the Eastern Conference standings with 89 points.
Miroslav Satan had a goal and an assist for the Islanders (34-26-10) and Drew Fata also scored.
New York lost their second straight game and fourth time in the past five outings.
Dunham was making his first start in 19 games and, after a scoreless first period, Kelly made it 1-0 two minutes into the second after Vermette lost the puck in the slot and Kelly caught up with it and slipped a low shot past Dunham.
Dunham didn’t look good on Corvo’s goal less than four minutes later.
Corvo threw the puck at the net from the side boards and it took a deflection off the skate of Islanders defenceman Marc-Andre Bergeron, fooling the goaltender to give the Sens a 2-0 lead.
Ottawa then blew the game open early in the third.
Neil scored on a wraparound two minutes in and McAmmond scored on a rebound 24 seconds after when Dunham lost the puck and got caught facing the wrong way.
Fifty-two seconds after that, Spezza capped off a tic-tac-toe passing play with Heatley and Patrick Eaves for his 29th goal of the season.
Spezza has at least a point in his past 15 games (nine goals, 17 assists), although it’s not recognized as an official streak because he sat out a game with an injury.
Wade Dubielewicz, making his first appearance of the season after being recalled from AHL Bridgeport on Wednesday, replaced Dunham following the goal.
Dubielewicz made eight saves the rest of the way and Satan broke Emery’s shutout bid late after the Senators took back-to-back penalties, while Fata got credit for a goal during scramble with 4.2 seconds left.
Notes: Neil’s goal was his 100th NHL point. … Left-winger Oleg Saprykin was a healthy scratch for the Senators for the second straight game. … Ottawa plays host to Philadelphia on Saturday. … Bergeron appeared in his 200th career game. … Islanders defenceman Sean Hill was a scratch. … The Islanders travel to Florida to face the Panthers on Saturday and wrap up their road trip Tuesday at Tampa.