WIHC ended in 2010.
ok so you want a treeco then fine but i can show you how to get more ok so we all know that you can't catch treeco in diamond or pearl so which is why on your Pokemon emareld Sapphire or any other game boy game where you can get treeco in have a least five other Pokemon and treeco wihc makes six pokemen then on pearl beat the elite four and unlock migrating ability and the migrate treeco oh and if you want a whole army of treeco start over your game boyonce a day catch six wild Pokemon and a treeco and migrat it remember u can only do it once a day