WoWDB

As Alayea says, having a group will make this substantially easier. However, it is possible to solo at times when the server population is low (the middle of the night) and when The Creeping Carpet of Ihgaluk (Alliance / Horde) is not a current daily.

Scout out several piles (at least 4-5) of Ihgaluk Roaches and plan a route to hit them all. After you hit them all quickly, just continue to head through areas where they are commonly found (on corners, around campfires, etc) and pray for the last 80-100. If there is -extremely- low population at the time and it isn't the daily for either faction, you can actually even plan the entire route out beforehand.

Almost impossible to solo simply because of competition. I recommend forming a group (or even a raid since this isn't a quest) for this achievement.