Bugs on Dahlias

My dahlias are about a foot tall, and about to bloom. I noticed tonight as I was watering that they seem to be covered with tiny black dots. They washed off with a strong stream of water, but what I need to know will they come back, what are they, and what can I do about them. They seem to be doing well other than these mite thingys.
Thanks Nancy Boston MA Zone 6a
Cham http://groups.yahoo.com/group/east-coast-wx /

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.