You can try two different methods or combine them.
If your site is new or you just started to place adsense code on the pages it may last some days until Google gets it right.

If this is not the case I’d try first the ad section targeting tags to show the bot what is important on your pages and what not. This works usually very well within about 24h.

The HTML tags to emphasize a page section are the following:

Here goes the text which you think should be important. You can use them several times on different sections of your page.

You can also designate sections you’d like to have ignored by adding a (weight=ignore) to the starting tag:

If this does not help you can enter your adsense account and use the competitive ad filter, where you enter directly the URLs you don’t want to appear on your pages.