Update [6/1]: Sold out at Amazon, but still at Walmart.

Amazon has the Spectracide Triazicide Insect Killer Granules For Lawns (10lbs) for $6 with free shipping on $25+ or with Prime (extra 5% off with 5+ items S&S order). Same price at Walmart.

Kills more than 100 insect types: kills insects above and below ground.