From the June 7 Turf iNfo for the North Central US blog and Dr. Roch Gaussoin:
Spring 2019, much like 2018, moved at a snail’s pace. One management practice that we have discussed previously and is closely linked with soil temperature is the application of preemergence herbicides.
Summer annual grasses, such as crabgrass, require optimal soil temperature and moisture to germinate and persist. Crabgrass and foxtail germination will occur when soil temperatures in a lawn at the 0‐2 inch depth are consistently between 60 and 70 F. For preemergence herbicides to be most effective, they must be applied before the soils reach this optimum temperature range. A soil temperature of 55 F (daily average) for several consecutive days is a normally reasonable based estimate for preemergence application timing. Less so in 2019. The extreme weather variability in 2019, when soil temperatures would have appeared optimal for application of preemergence products was followed by snow, frosts, and a decrease in soil temperatures throughout Nebraska. If you just couldn’t help yourself and applied a preemergence application in early to mid-March, the applications will still be effective early season, but you will want to closely monitor any late spring or summer crabgrass emergence that will require postemergence control. As an FYI, the forecast for June is drier and warmer than normal. This time of year, especially in turf thinned by drought, disease, traffic or other afflictions, crabgrass and other summer annuals may pop up, especially if the preemergence application was applied early and not followed by a second application. Also, no product is 100% effective even when applied correctly.
“Escapes” may occur for a number of reasons including misapplication. Regardless of the reason or type of turf area, older and larger crabgrass is much more difficult to control than younger plants, making early to mid-season the optimal time to control crabgrass post emergence. Waiting to treat when the crabgrass is more visible and tillering will result in the need for higher herbicide rates, increased risk of damage to desired turf and decreasing control.
Lawns, sports turf, fairways and golf course roughs:
Drive and other quinclorac-containing products will control young to tillering crabgrass effectively as long as the appropriate spray adjuvant is used. Tenacity, Acclaim (fenoxaprop), NuFarm’s Last Call (fenoxaprop + fluroxypyr), or BASF’s Pylex will control crabgrass as well as other weeds listed on the label. Be sure to check the label for specific species, rates, and precautions (including overseeding limits) as well as the need for a spray adjuvant.
Be sure to comply with all label restrictions and instruction. Mention of a trade name does not imply endorsement by the University of Nebraska or non-endorsement of products not mentioned.
Roch Gaussoin, Professor and Extension Turfgrass Specialist, rgaussoin1@unl.edu