Posted: June 11, 2012
The following information is being sent with permission from Zac Reicher, Professor, Turfgrass Science at University of Nebraska-Lincoln. He posted the following timely information about weed control. Check out his other posts!
Crabgrass update: Time for sequential apps, watering in, postemergence products, etc. June 7, 2012
Some quick points on the sequential application of PRE’s:
- Though timing of the sequential application is flexible, usually anytime in June will suffice.
- Our recent research indicates it’s not critical to use the same active ingredient for the first and second application. Watering-in preemergence herbicide with 24-48 hours should improve control.
- If applying a granular application, use the proper product to minimize the rate of N applied.
- If reseeding will be needed in August due to thin turf, renovation, etc., reconsider the sequential application in favor of a postemergence (POST) product. Depending on application rate, product, environment, soil type and other factors, there may be enough residual from a late PRE application to affect germination.
If the initial application has already failed (not likely) or applying to a previously untreated area that has crabgrass visible, use a postemergence (POST) product to control current crabgrass plants and a PRE to prevent future germination. Crabgrass may continue to germinate for another month or more.
Products to choose from include:
- Dithiopyr (Dimension or Dithiopyr) – Primarily a PRE herbicide but has good POST emergence activity on crabgrass before it is tillered, so is a great product to use now.
- Quinclorac (Drive, Quinstar, Quinclorac, Solitaire) - has only POST activity on crabgrass, so combine with pendimethalin, prodiamine, or dithiopyr. It will control crabgrass beyond 4 tillers, but is more effective on younger plants. Be sure to combine with methylated seed oil if mentioned on your specific label.
- Fenoxaprop (Acclaim) -has only POST activity on crabgrass, so combine with pendimethalin, prodiamine, or dithiopyr.
- Mesotrione (Tenacity) – POST activity to fairly large crabgrass in established stands, so combine with pendimethalin, prodiamine, or dithiopyr. Also controls creeping bentgrass, nimblewill, and other weeds. Labeled for spot applications on established lawns or blanket applications on new seedings.