The Bulldogs kept the home side goalless in the second half, as the Roos registered two behinds, but it was a second-quarter blitz from Merrigum that helped clinch the 12.16 (88) to 4.9 (33) win.
Three goals each from Josh Smith and Jack Sinclair alongside the performance from Reidy steered the Bulldogs to an opening round win in the Kyabram District League.
The 28 scoring shots for Merrigum displayed its tight-grip on the contest, with poor accuracy on goal restricting the final margin.
The preview match of the round lived up to its hype as Avenel powered past Lancaster to claim a 11.12 (78) to 9.9 (63) win on its home deck.
Gun Avenel recruit Dean Giles was best for his side and Chris Burton slotted home four goals for the Swans.
Lancaster skipped 16 points clear at quarter-time, but was kept scoreless in the second term as the Swans steadied the nerves and applied scoreboard pressure.
Wombats pair James Ross and Zach Cerrone (three goals) did their part in trying to claw their side across the line.
Shepparton East enjoyed a comfortable win in its debut appearance in the competition, registering a thumping 142-point win against Longwood.
Rejuvenated Eagles veteran Mark Frost kicked five goals and former Longwood brother pair Ben and Anthony Tautala slotted eight goals between them as they won 24.18 (162) to 3.2 (20).
Reigning premier Tallygaroopna started its title defence with a 112-point demolition of Dookie United.
Tyson Sidebottom slammed home six majors in his best afield performance, as Tally turned off the power in Dookie’s forward half, with the away side kept goalless after quarter-time.
Murchison-Toolamba pair James Peck (seven goals) and Adam MacGibbon (six) helped their side to an emphatic 143-point win against Rushworth.
The 24.14 (158) to 2.3 (15) win was the perfect way for the Grasshoppers’ new coach Nick Iorriani to settle into the role.
In the final match of the round, Matt McCarty made a good first impression at new club Violet Town with 13 goals in his side’s 30-goal rout of Ardmona.
Mark Baker, who followed McCarty from Waaia to the Towners, chipped in with six goals in the 36.16 (232) to 6.13 (49) win.