Well Mosh...I'm glad you asked.
There is only two sure fire ways of curing this problem...and here they are.
Solution number 1
Heres what you'll need - 1 litre of high quality lubricant, a possum costume, a stereo playing porn music, some possum nibblies...laced with LSD, a disco light, a possum sized strap on, an extension cord, a 4 point power pack , a whip and some gaffa tape
Step 1 - Whilst its still daylight, Run the extension cord out into the bushes and connect the disco light and stereo
Step 2- using some bowls place some LSD laced possum nibblies (possum bait will do) around the bushes where these raunchy critters get down and dirty.
Step 3- Wait till night fall and wait until the possums are off their rockers on the LCD...you can tell this because if you look out your window you should see a couple licking the trees thinking its ice cream, a few will be staring at their little paws and if youre lucky you might even see one or two trying to snort their own tails.
Step 4 - Now that the little perverts are sht faced..its time to get to work..put on your possum costume...complete with 1 possum sized strap on.
Step 5 - switch on the disco light...this will have 2 effects. 1. It will freak a couple of them out so bad and they'll never come back thinking its aliens and 2. It will set the mood for whats to come.
Step 6 - Turn on the porn music and make your triumphant entry in your possum suit.
Step 7 - Now here's where you need to set your morals aside and just trust me...now that youre in amongst the possums and theyre spinning out over the size of you..you need to grab one of the little fuckers...pin it against the tree and fucking rape it...HARD.
Step 8 - Grab the next little prick that comes to hand..tie his little paws together and secure him to a tree using the gaffa tape...now whip the little deviat until it cries.
Step 9 - Now grab one by the throat..pull it close to your face and begin screaming and moaning as loud as you can in its sensitive little ears...then grab its tail and insert it up another possums arse.
Step 10 - Rinse and repeat until they have either run off in terror or a curled up in the fetal position rocking back and forth.
The basic idea of this is to have the tripping little buggers think their at a swingers party/orgy thats gone horribly wrong.
Caution - Every now and again you may come across one that seems to be enjoying this alot...you've found yourself a pervert possum and he will keep tapping on your window asking for more...the solution to this is write it a love letter and dote on it...it will think youre too clingy and piss off as well.
Solution 2 - Whilst not as fun..this can work. Possums sleep during the day..so simply rig some cheap speakers all around the trees they live in and constantly play thruought the day the sounds of you and youre misses doing the dirty...lets see how they like it!!!!
Hope that helps,

Chalice