Stickers or Burr Weed can be a big issue during the summer.  To understand how to get rid of them you have to understand how they develop.  It is actually a winter weed that germinates in the fall but grows and develops late winter/early spring.  When it gets hot the weed dies. The seed heads they develop is what forms the sticker and causes you issues.  The easiest way to get rid of them is with a pre-emergent in the fall.  This will keep the weed from ever developing.  If in the Spring you see the weed growing you need a herbicide like Speed Zone Southern or MSM.  Make sure to read and follow the label.  The key to kill it is to catch it early enough before the seed heads start to develop.  If you wait too long then even if you kill the weed, the seed head will still get hard and cause issues.  If you currently have stickers right now then unfortunately you don’t have any options. You can use a bagger mower to suck up some of them but it wont get all of the stickers.  It will be important to remember though having stickers that are dead means the seed heads developed and they are in the soil for next year. You can be proactive and apply a pre-emergent in the fall or wait until next spring and kill the weed while it is young.  Here are a few links to the products we are talking about. Hope this helps!          

Specticle Flow Pre-Emergent:

Speed Zone Southern: