England, trying to avoid an unprecedented multi-series whitewash, stumbled to 3-64 at tea on day one of the day-night clash after being sent in to bat on Thursday.
Garth (2-13) struck in the first over, dismissing Maia Bouchier (2) thanks to a stunning catch by wicketkeeper Beth Mooney.
The Irish-born star later claimed the crucial wicket of England captain Heather Knight (25), who looked set to deliver on her promise of playing her best when she has a point to prove.
Knight was trapped lbw, not even bothering to use a review as she walked off to leave star Nat Sciver-Brunt to bat with Sophia Dunkley.
Sciver-Brunt (20no) and Dunkley (6no) survived to the break, with their partnership set to be crucial to England's fortunes in this Test.
Quick Darcie Brown (1-26) took the other wicket of the session, removing opener Tammy Beaumont (8).
Australian teammates congratulate Darcie Brown (second left) on the wicket of Tammy Beaumont. (James Ross/AAP PHOTOS)
Earlier, rising star Georgia Voll was confirmed to make her Test debut, even after captain Alyssa Healy proved her fitness.
Under a cloud after missing the Twenty20s with a foot injury, Healy was trusted by selectors to make it through the first women's Test at the MCG since 1949.
She won the toss, electing to send England in to bat as Australia chase the first 16-0 points whitewash since the multi-format Ashes was introduced in 2013.
Introducing Australian Women's Test cap #185, Georgia Voll! 🙌— Australian Women's Cricket Team � (@AusWomenCricket) #Ashes pic.twitter.com/EIDc8BX4rsJanuary 30, 2025
"I'm really excited," Healy said at the toss.
"A long time coming (to be back playing).Â
"(There's been) a lot of talk about this series in general, but we're part of the way through it. Four more days of good tough cricket to go."
Voll was presented with her baggy green by Australia legend Belinda Clark.
The 21-year-old will open the batting with fellow young gun Phoebe Litchfield, with Healy shifting to No.4.
Alyssa Healy an hour out from the toss... — cricket.com.au (@cricketcomau) #Ashes pic.twitter.com/oFPhWVuFFIJanuary 30, 2025
Healy isn't taking the gloves in this match, with Mooney to continue wicketkeeping after handling it well during the T20s.
A small crowd of about 6000 people were in the stadium during the first session, with Cricket Australia hoping for a strong turnout once work and school finishes for the day.
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