Organic mulch is best for repelling bugs, according to SF Gate. Mulches made from cedar and cypress wood are particularly effective. Inorganic plastic mulch offers some protection against insects but is not as versatile and effective as organic mulch.
Mulches made from straw and cocoa bean shells also repel bugs. Straw mulch is a popular choice among gardeners because it discourages insects from laying eggs and wards off fungi.
Cocoa bean shells repel bugs because of their chocolate aroma and are especially effective against slugs. Cocoa bean mulch also repels termites. Despite its pleasant fragrance, this type of mulch is unsafe for use around dogs and small children because it is potentially toxic to them.