SharePoint 2013: Stop Crawls using PowerShell

Run this Script in PowerShell to stop all your Crawls:

Get-SPEnterpriseSearchCrawlContentSource -SearchApplication "Search Service Application" | ForEach-Object {$_.StopCrawl()}

You could also start full Crawls on every Content Source changing the StopCrawl command like this:

Get-SPEnterpriseSearchCrawlContentSource -SearchApplication "Search Service Application" | ForEach-Object {$_.StartFullCrawl()}