One might be forgiven for thinking, "Wicker is easy to clean!". However, proper care of wicker is needed to ensure that mould and mildew is avoided, and that the wicker lasts for a good long time before losing it's strength.
If you do notice mould or mildew on the surface of the furniture, it should quickly be removed using a weak solution of water and bleach. Maintain even humidity in your home around the chair, and if kept outdoors try and prevent the wicker being kept in harsh conditions (be that sun, snow or rain). Spills can easily be wiped up with a solution of light detergent and water on cloth. Vacuuming still works with these more natural weaves, provided that a soft brush attachment has been attached to the vacuum!