It's both the pesticides/fungicides and the disappearance of native plants (aka 'weeds') from gardens. Not to mention those nurseries and landscaping companies that aid and abet the consumer taste for non-natives.
And then of course there's all the media coverage encouraging fear of bees and distaste for bugs, with the implication that a happy yard is a bug-free one. We need change on so many levels in order to stop these trends...