Seeders are big creatures from Gears of War that fire Nemacyst spores out of their backhole. They've been known to jam radio communication.
When you fight them, they are stationed in the hole they dug. They can fire them in both long and close range. They can also take down King Raven helicopters with this attack.
The only way to kill a seeder is by firing a Hammer of Dawn
at it. Don't worry, there will always be one there for you nearby.