It looks more like fungus when the photo is enlarged and the blotches look more spiderwebby. Regardless, try wiping the lens with some lens cleaner or alcohol and a gentle cloth.
Before you get too far into this:
- Check the camera to make sure it didn't have batteries leaking and corroding the battery compartment.
- Remove lens from camera if you haven't already
- Silica gel is just for keeping the moisture down in storage. It won't stop or clear up existing fungus/damage. To stop the fungus, expose the lens to UV, like put it in the sun. However, if there is a lot of fungus, the damage from etched glass will remain.
- The lens (a Sigma 35-80 slow zoom) is sort of a bottom of the barrel kit lens anyway. Don't be afraid to give up on it. If the camera body is ok, get a clean lens like a Canon 50/1.8 (or 28-80 if you must have zoom) and have fun.