Back in April, Google began showing trending searches in the autocomplete search box within the Google Search App. It is cool, but tapping in the search box to see trending searches, is not always that relevant and many searchers didn't want to see it.
So Google, a week or so ago, announced quietly in an ongoing Google Web Search Help thread that you can now opt out of these trending searches. To do so, you must be on the Google Search App versions 6.1+. Then go to Google Now, click on the menu (three-bar icon) and select Settings. From settings choose Autocomplete and then toggle off the "Show trending searches."
Here is what trending looks like in the search box: