You need to find some spider repellent.
Visit the roadblock and car wreck. You will find a pest control truck.
You need a tool for that. ?
Use a crowbar you find at the gas station
There are four cans of bug repellent inside the truck.
Look for clues. You should find a sticky note with references to the can codes (B-11, B-36, A-13, A-18).
If you manage to find bite marks they should match to one of the spiders depicted in the sticy note.
There's a dead body at the roadblock. Look at the left one to find the bite marks.
The spider teeth should match the bite marks. Count the amount of teeth and compare the sizes of the teeth to the bite marks. These will vary on different playthroughs.
Now you need to spread the repellent around the farmhouse for the night.