How can I remove slug slime from my house siding?
Thank you for writing to eXtension.
Your immediate problem - getting the slug trails off the side of your house - is going to take a little elbow grease. The slime is organic, and in my experience usually breaks down in the rain and sunlight over time. It can be speeded up with various cleaning agents that are designed for outdoor use and some light scrubbing. If this does not appear to work, I'd suggest visiting your local hardware store for some suggestions.
Most importantly: DO NOT USE GASOLINE AS A CLEANING AGENT OR PEST CONTROL PRODUCT!!! This is extremely dangerous, and is an illegal use of the gasoline (take a look at some of the warning signs on the gas pump the next time you fill up...each warning was put there because somebody, somewhere, blew himself up doing that).
To prevent a reoccurrence of this problem, you will want to control the slugs in the garden. This publication from Purdue outlines the best ways of controlling them: http://extension.entm.purdue.edu/publications/E-45.pdf. Most likely, there's an abundance of moisture near the foundation, possibly for watering landscape plants. If you can reduce some of the excess moisture, that will also help to control them.
If you have any other questions, please let me know.