Question: ![cotton or mold like fungus](https://i.stack.imgur.com/Ipsza.jpg)

Found this in my areca palm trees planted in ground. The place is moist and recieves lesser sunlight.

Should this be treated with some fungicide or just a raking of soil would do ?

It is winter here with 8-10 degree centigrade.

Answer: 
I suspect the hyphae (the fungal growth you can see) is actually associated with the debris sitting on top of the soil and nothing to do with the roots of the Areca. It's difficult to be sure what the debris is, looks a bit like pine cones or something. Remove the debris and see if there's anything else under there this might be growing from; I'm not sure what the roughly rounded, blackened area covered in fungal strands (to the right, at the base of the trunk) is - can't tell if it's part of the tree or just more debris, so have a closer look at that. If that's just debris, remove that too. if it's not, post another picture once you've cleaned up the area.

Ongoing, keep the area clean - if it rarely or never receives sun, then best to keep it clean to prevent this sort of thing.
Fungus and mold like cooler areas that are more moist. What has happened here is the soil is moist and temperatures are cooler. You can scoop up the "bad" soil with the fungus and throw it in the garbage. Watch out if the plant starts to get sick and looks bad. 

I use this mixture on my seedlings indoors to prevent mold and mildew: 1 part hydrogen peroxide and 10-15 parts water. You can try using that on your plant only if it looks sick. 

Otherwise let the soil dry out completely around this plant before you water it.