The best replacement for preen is roundup.

The best alternatives to preen are rated as following:
★★★★★  roundup
★★★★  snapshot
★★★  scotts
★★  casoron
★★  corn gluten
★  treflan
★  round up
  halts
  caseron

Your alternative for preen is not listed? Suggest!
Speaking about preen, one probably shouldn't forget about mulch.

Other search terms related to preen and their ratings are:
★★★★★ mulch
You have in mind a companion for preen and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of preen in all years. Click on graph for more.
preen
roundup
snapshot