ALL: How do you apply crabgrass pre-emergent herbicides?

All at once w/out fert
All at once + fert
Split app: both + fert
Split app: 1 + fert & 1 - fert
Corn Gluten Meal

Update (03/30/15)


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Spring Time Temperatures Arrive A.  After a cool start, March temperatures have bounced back to give Missouri it’s first taste of spring.  - Source: Pat Guinan   B.  Over the previous 30 days, I-44 is just about the dividing line between above normal pre

Redbuds are budding, daffodils and forsythia are now flowering, so in tune with the calendar, spring appears to happening right about on schedule.  Despite a few cooler days on the books, March is rounding out to be just about normal temperature-wise in Missouri.  Soil temperatures have also dipped back down into the mid 40’s and low 50’s, which is just a shade below normal for late March. 

Almost along I-44, precipitation over the last 30 days has been sharply divided in a diagonal line across the state.  The Bootheel and SE portion of the state have had well above normal rain (and snow) fall, while western and northern areas of the state are below normal.  The Kansas City area and Kansas as a whole have been particularly dry, and are beginning to enter into a lower level drought stage.  As you may well know, California and Nevada are currently embroiled in a very severe drought situation, along with Oklahoma and portions of Texas (see U.S. drought monitor here).

Temperatures look to rise over the next week in the region, as the jet stream retreats north. Over the next 6-14 day window, there is a probability of higher than normal temperatures; meaning spring greenup should start kicking into the next gear. There is a higher than average chance of precipitation over the next two weeks for St. Louis and the eastern portion of the state, while chances drop in western portions of MO and into Kansas.  Click here to view forecast maps from the NWS.  

Quick Hits

Pink Snow Mold in a NTEP Cultivar Trial A. A mild outbreak of pink snow mold was observed on our NTEP creeping bentgrass putting green trial. B. List of commercially available cultivars in the NTEP bentgrass trial.

  • Pink Snow Mold (Microdochium Patch): After scouring the research farm, we did discover some pink snow mold evident on some cultivars in our newly established creeping bentgrass trial.  This disease is only a severe problem on bentgrass in Missouri, and particularly on newly seeded areas (this trial established last fall).  The disease can continue into mild, cool temperatures in the absence of snow cover as Microdochium patch, and can be especially severe under frequent rainfall or high humidity conditions.  Therefore, if symptoms are currently present on golf greens, a curative fungicide application should be applied.  Several, including fludioxonil (Medallion™) or a combination of chlorothalonil (Daconil™) and iprodione (Chipco 26GT™), are labeled and effective for halting disease progress.  A light verticutting may also break up the matted patch symptom and enhance recovery.  

    On another note, we have established several new cool-season NTEP cultivar trials at the MU research farm. These include a creeping bentgrass putting green trial (highlighted above), a creeping bentgrass fairway height trial, and a fine fescue trial.  If you are planning on regrassing and would like to view these trials in person, feel free to give us a call and stop by.   

The Signs of Spring

Phenology & Numbers Indicate Spring  Even a bush conservative forsythia is a flowering indicator of spring. 3/28/15: Current 5 day average 2” soil temperatures and accumulated degree days (base 32 and base 50) from across the state.

Other than this sign, several other substantial spring indicators are occurring throughout the state.  Even my shaded “Bush conservative” forsythia next to my office is blooming, so the time is nigh or well upon those maintaining cool season turfgrasses to get out and get moving.  Spring fertilization of cool season turfgrasses is best done now or within the next 2-3 weeks.  On tall fescue or tall fescue/Kentucky bluegrass lawns, this fertilization can be applied now in combination with a preemergent.  If attempting to use corn gluten meal for weed control, remember that about 10% of the 20 lb/1000 sq ft rate is nitrogen, so 2 lb of slow release N/1000 sq ft will also be added. 

The window of crabgrass preemergent application as outlined by Michigan State’s is 250 – 500 base 32 degree days, and, as shown in the above figure, we are well into that range.  We also are in the range in which Proxy + Primo tankmixes should be applied on putting greens to inhibit Poa annua seedhead formation.  Higher forecasted temperatures put an onus on getting these applications out soon.  If utilizing a split application strategy for preemergent herbicides on lawns, leave out the fertilizer in the 2nd application in or near May.  This late spring fertilizer application will cause a boost in leaf growth and resultant predisposition of tall fescue to brown patch infection.  Other questions on crabgrass control are expertly answered in this recent article posted by Dr. Aaron Patton in the Purdue Turf Tips.  

As noted in the previous update, we are still a bit early for any preventive fungicide applications to creeping bentgrass putting greens.  Warm season turfgrasses haven’t greened up yet either, but if maintaining zoysiagrass, large patch should be of concern soon after appearance of green tissue.  As noted last fall in this update, our research has shown very good results in applying a single fungicide application before or shortly after greenup (early or late April) to control large patch outbreaks in May and June.  Therefore, if you have a zoysiagrass lawn or fairway that 1) had noticeable large patch symptoms last fall, or 2) severe symptoms in the past, and 3) was not treated last fall, consider making a preventive application this spring at or before the first mowing.  If only one fungicide application can be made in the future to these susceptible sites, utilize a spring application timing instead of fall to minimize control variability in the spring, when longer term large patch suppression is most needed.


Lee Miller
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Extension Turfgrass Pathologist
University of Missouri