We present 3.6 to 70 \mu m Spitzer photometry of 154 weak-line T Tauri stars ( WTTS ) in the Chamaeleon , Lupus , Ophiuchus and Taurus star formation regions , all of which are within 200 pc of the Sun .
For a comparative study , we also include 33 classical T Tauri stars ( CTTS ) which are located in the same star forming regions . Spitzer sensitivities allow us to robustly detect the photosphere in the IRAC bands ( 3.6 to 8 \mu m ) and the 24 \mu m MIPS band .
In the 70 \mu m MIPS band , we are able to detect dust emission brighter than roughly 40 times the photosphere .
These observations represent the most sensitive WTTS survey in the mid to far infrared to date , and reveal the frequency of outer disks ( r = 3-50 AU ) around WTTS .
The 70 \mu m photometry for half the c2d WTTS sample ( the on-cloud objects ) , which were not included in the earlier papers in this series , and , are presented here for the first time .
We find a disk frequency of 19 % for on-cloud WTTS , but just 5 % for off-cloud WTTS , similar to the value reported in the earlier works .
WTTS exhibit spectral energy distributions ( SEDs ) that are quite diverse , spanning the range from optically thick to optically thin disks .
Most disks become more tenuous than L _ { disk } / L _ { * } = 2 \times 10 ^ { -3 } in 2 Myr , and more tenuous than L _ { disk } / L _ { * } = 5 \times 10 ^ { -4 } in 4 Myr .