SA and Portugese millipedes? ;)

Use this, Carbaryl spray,

http://www.bayercropscience.com.au/resources/uploads/msds/file7346.pdf

with one of these,

http://www.bunnings.com.au/products_product_hills-5l-garden-sprayer_2534.aspx

Lay a 1metre wide barrier on base of exterior walls, steps and deck.

Avoid contact with skin and breathing mist.

But I would be mowing grass and removing all of those yummy weeds and leaf litter between seasons too.  They love Paterson's Curse - or Salvation Jane to a SA resident.

Compliments of an Aussie farmer. 

Milipedes are harmless and feed on dead decaying vegetable matter and are real recyclers in the plan of things in the garden. Also they provide a valuable food supply for birds. They live in damp leaf litter so it may be an idea to remove any surrounds where they affect you.

Use of chemicals will do you more harm than the Milipedes.

Thank you, they started appearing after I had flower beds mulched so I guess the first way to go is to remove that mulch off,from what is basically black sand, and away from the house. Once again thank you.

vivity,

I would be astounded if there weren't plants that would deter the pests and you could grow as borders and between plants.

Since you will have to cut down on watering to put off the pests, why not grow a heap of mint around and in some beds?  They probably don't like mint.  Many varieties and useful in the kitchen. 

Some ideas,

common mints

catmint (catnip)

ageratum

citronella

marigold

lavender

Just get a number of these plants and run them around the beds.  But you must also intersperse them with your crop/flowers to confuse the millipedes.  Observe and thin to keep what works well (you will know that from few millipedes near them).

Some of the low growing coastal shrubs that are aromatic (crush and smell b4 selecting) also deter lots of bugs.  Worth trying too.

If you find plants that work, gradually re-introduce mulch (NOT pine mulch) but water sparingly and infrequently.

Finally, write up your results and apply for a guvvy grant to study further  :)

Failing all that, Mr Bayer.