If you are on version 10+, you can click on the query from the main trend page and select to exclude it from the chart.
If you really want to exclude the hash from monitoring completely, you can go to advanced options for that instance, click support options, and edit this option: QUICKPOLL_WHERE_CLAUSE
Follow the info in this KB to exclude things. Be warned though that there can be unintended consequences with excluding it from the quickpoll. If that hash or SP or whatever you are excluding suddenly goes off the charts, you will be blind to it in DPA.
Thanks mandevil. I will try to work through this knowledge base suggestion...