Joseph (5/29) snagged the first five-for of the season in either women’s format and supported by Emily Hinze’s 3/26, the Browns were dismissed in 38 overs for just 137.
Katelyn Pope (47) and Sarah Ferris (22) both played important innings with the bat, however the Eagles passed the required total inside 45 overs.
Eagles veteran Caroline Ward compiled an unbeaten 54, while Pope did her best to restrict them, taking 3/24.
A spread of double-figure scores from the Sturt batters, plus a dominant performance with the ball, secured victory for the Blues.
Batting first, Sturt reached a total of 8/204, thanks to contributions from Eliza Bartlett (24), Brooke Harris (35), Dani Reid (36), Jasmin Earl (25), Amelia Rault (15) and Sharni Tansell (16 not out).
Hannah Sampson was the best of the Southern District bowlers, taking three wickets.
In reply, the Stingrays lost wickets regularly, with number nine batter Callie Wilson (14 not out) providing some late resistance.
Two wickets each from Tansell, Harris and Rhianna Peate helped to dismiss the Stingrays for 89 in the 31st over.