You can get by without the base resistor. If you will be flipping power on/off a lot, and want to make sure the transistor stays off until it's turned on, you can use an inverter circuit like this one http://www.rentron.com/IRTORF_TX.gif
The 10K pull-up holds the base at logic 1 keeping the transistor off while the PIC powers up. If it's battery operated a small FET would be a better choice than a transistor.
I drew another quick schematic for you. Either receiver inverter will work, but the NPN circuit would be best.
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