Wind Zone didnt work for model from SpeedTree

HI
Just exported model from SpeedTree to Unity with wind
Added WindZone to terrain, but wind doesnt work(It works very very very slow, i cant even see that)
And after some time its going little faster and fasterwith a time
What s the problem?

ANd i think i know why
I havent got this[117874-екуууу.png|117874]