We present 24 \micron Spitzer /MIPS photometric observations of the \sim 50 Myr open cluster IC 2391 .
Thirty-four cluster members ranging in spectral type from B3-M5 were observed in the central square degree of the cluster .
Excesses indicative of debris disks were discovered around 1 A star , 6 FGK stars , and possibly 1 M dwarf .
For the cluster members observed to their photospheric limit , we find a debris disk frequency of 10 _ { -3 } ^ { +17 } \% for B-A stars and 31 _ { -9 } ^ { +13 } \% for FGK stars using a 15 \% relative excess threshold .
Relative to a model of decaying excess frequency , the frequency of debris disks around A-type stars appears marginally low for the cluster ’ s age while that of FGK stars appears consistent .
Scenarios that may qualitatively explain this result are examined .
We conclude that planetesimal activity in the terrestrial region of FGK stars is common in the first \sim 50 Myr and decays on timescales of \sim 100 Myr .
Despite luminosity differences , debris disk evolution does not appear to depend strongly on stellar mass .