Giacomo: I can't help you with quassia chip supply, but one possum deterent that works reasonably well here, and that doesn't have to be re-applied after each rain, is some stuff called "Treepel" This is a concoction that you mix yourself as required from egg powder and paint resin. It is OK thru a sprayer to a degree, but I prefer to use a pump bottle. This is a kiwi-produced product, (I think!) and is said to deter hares, rabbits possums and sheep.
Hope this is of some help to you.

Hi Gia, got this receipe for possum repellant,
1 cup human urine
1 cup household ammonia
4.5 litres of water
Spray around know areas where possums are using to deter them. Another is to use cayene pepper, mustard powder, ground up fine tabacco powder to deter them.

Here is a link that might be useful: UGA

I've had this problem... possums eating all my new pear trees!

I set up an electric fence along the top of my paling fence. The possums were using the paling fence as "possum highway" to get to the trees. They can't walk along the fence now (without getting a bit of an exciting shock!) and I put upside down pots with holes cut in them around the trunks of the trees so they can't climb them.

Works wonders! Just find a rural supplies store and take it from there.

Derek

My garden is shady but I was determined to grow some roses. Alas possum and/or bandicoots eat the new buds but this year I have had great success with chilli powder. I buy it bulk, sprinkle around the bases and also sprinkle a bit over the roses. My night time visitors do not like it on their paws and have moved to another neighbourhood. It is worth a try.

My possums EAT the chillis on my chili plants so I don't think a chili spray will help! They must be a hardy breed in N Qld. I have now tried planting a chili in the same pot as a lemon-scented geranium. It seems to be working so far but the ammonia spray will be worth trying if they become accustomed to the geranium.

It has now been two years since I posted this item, and the only thing that has been successful in keeping away possums has been an electric barrier (as suggested by DeKa, above). I have been very happy with the "Pet Master" kit manufactured by Gallagher; it is totally effective and would be very useful for deterring cats and dogs also. See website below:

Here is a link that might be useful: Gallagher

Hi Guys
A fence with a floppy top will keep out most possums and it does help a lot if you have a "hotwire connected to it as well....it is also very effective to use large quantities of blood and bone in your soil around the fence line....I mean would you go inside a fence that smelled of decaying carcases...in order to dine
You can also try the trapping and training method of deterring them...this is very effective and the longest lasting method
cheers
Peter

Blood and bone is said to be a deterrant as well
cheers
peter

Hi All, POSSOFF is now available at BIG W garden dept and other chainstores and works. Good luck Peter.