Batting first after winning the toss, Karnataka notched a challenging 296 for eight in the allotted 50 overs.
Ravikumar Samarth top-scored for Karnataka with a brisk 117 off 115 balls as the Vijay Hazare Trophy winners closed in on 300 at the Himachal Pradesh Cricket Stadium.
Manoj Tiwary slammed a breezy century (120 off 110 balls) and anchored India 'B' chase, but his dismissal in the 42nd over triggered a collapse that saw the team stop at 290 for nine in 50 overs.
However, India 'B' lost their way after Tiwary was sent back by leg-spinner Shreyas Gopal, and even Lad could not help his team cross the line.
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Tiwary's knock was laced with 10 boundaries and four sixes, while Lad found the fence six times.
Gopal was the most successful bowler for Karnataka, returning figures of 3/29, while off-spinner Krishnappa Gowtham took the wicket of Lad at a crucial juncture.
Earlier, Samarth's knock was the pivot around which the Karnataka innings revolved. He hit 13 boundaries and a six.
In-form opener Mayank Agarwal smashed 44 off 40 balls, but skipper Karun Nair missed out after getting out for 10.