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Update (5/7/2012)

Don't Feed Your Lawn Now...
Don't Feed IT!!

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Much needed rain across Missouri, particularly KC

Precipitation finally hit the Kansas City area over this past weekend with 1.5-3” received over the past 48 hours.  As the figure above shows, and as noted in the last update, the area was getting woefully dry.  Now the driest area of the state is in the Bootheel which has only received about 1-1.5” of precipitation over the last 30 days (3-5” below normal).  Preceding the weekend rainfall, temperatures neared summer (or should I say March?) levels with highs topping out in the high 80s/low 90s.  Even more important the nights were warm (high 60s/low 70s) and muggy, which led to heavy dews and the initial signs of our nastier summer turf diseases.  Forecasts are granting us a reprieve over the course of the week, and cool-season turf should be favored over pathogens.  It also should cool off our soil temperatures, which rose well above normal temperatures with the weekend heat. 

Soil temperatures above normal in Missouri

Quick Hit

Large patch and residual insect damage noted in zoysia lawns in St. Louis
  • Zoysiagrass Lawn Issues:  Many, many problems have been reported in St. Louis over the past two weeks on zoysia lawns in Missouri.  Diagnostic visits and samples were received from 5 lawns just last week.  For the most part, the downtrodden homeowners comment the problems started in August of last year and never recovered this spring.  Active large patch outbreaks were noted in 4 of the 5 lawns. Two lawns also had noticeable insect damage which included “frass” and hollowed out stems.  The most likely insect culprit would be hunting billbugs or chinch bugs which can devastate a zoysia lawn quickly.  These problems are a cautionary tale that zoysiagrass maintenance is not worry free, and the bulk of maintenance (disease & insect control, irrigation, fertilization, and thatch removal) must be done when it’s hot, you are uncomfortable, and sweating.  Brad Fresenburg and I wrote a short article detailing these problems, which can be found by clicking here.  Diagnosis of a zoysia problem is very difficult when done a season or two post-mortem.  Therefore, if zoysia starts to wane get a sample in quickly for identification of the problem.   

Dollar spot raging in Missouri on creeping bentgrass
  • Dollar Spot:    After the last weekend’s perfect conditions, dollar spot is raging on our research greens now.  Our dollar spot activity started in late March this year, about 4 weeks ahead of schedule.  As expected, the damage is worse on our “disease green” which we inoculated last year and now has a quite large pathogen population.  It is important to stay on top of fungicide applications in high amenity areas.  On creeping bentgrass greens and tees, it is possible to recover from infection quicker with a small shot of nitrogen.  On Kentucky bluegrass lawns, however, I would advise against this strategy, because as noted below, we are heading down the home spring stretch to the summer disease season.         

No "may" regarding May lawn fertilization

May is not the time to fertilize lawns in Missouri

This means that spring is fading quickly, and managers should have their sights squarely on summer disease (& insect) management.  At the end of the month, long residual insect controls for annual white grubs, chinch bugs, and hunting billbugs will be in order, and preventive disease control will be on the to-do list for cool season turf hit hardest by brown patch and Pythium last year.  However, it is what you don’t do now that may have the largest impact on lawn disease management now. 

May is the single worst month to fertilize any lawn turfgrass in Missouri.  Zoysiagrass is not running at full speed, and large patch is still impacting many lawns in the area.  For tall fescue, managers should want concentrated root growth now while they can get it, not the shoot growth that is prioritized with a May nitrogen application.  As the kicker, nitrogen applications now will cause both tall fescue and zoysia to be much, much more susceptible to disease. 

Nitrogen applications lead to lush shoot growth, and a more pleasing green color that many homeowners seek.  The booby trap in this aesthetic treasure is the impact nitrogen has on leaf cell morphology.  Leaf cells swell with nutrients like the hot air balloons pictured above, and their cell walls become very thin.  Like a balloon, these cells are much easier to pop by a penetrating pathogen mycelium and the plant is much more susceptible to infection. The three most prevalent lawn diseases in this region: large patch of zoysia, brown patch and Pythium of tall fescue, take full advantage of this actually weaker plant when the summer heat favors severe epidemics.

Another hidden danger at this time is Weed-n-Feed products which can deliver 0.8-1 lb N/1000 sq ft along with the herbicide.  These products should be applied in fall when the nitrogen is needed for recovery and control of broadleaf weeds with herbicides is more effective.  If a herbicide is necessary now, a three-way product without a fertilizer is recommended. 

I love the commonly running commercial that exclaims in a Scottish voice: “Feed your lawn now, feed it!” or even “Seed your lawn now, seed it!”.  However, I couldn’t disagree more with both of those sentiments this late in the spring.  Reserve your best Scottish imitations for September for tall fescue and the summer for zoysia, and the grass will laugh along with you.

For more information regarding the dangers of spring fertilization click here for an article in the Missouri Environment & Garden Newlsetter.  

Reminder: Spring Dead Spot Samping
If you currently are noticing spring dead spot symptoms on your field or course, please email Derek at or me so we can schedule a visit and take a bit of disease away from you. 

Save The Date: July 10th
University of Missouri Turf & Ornamental Field Day
More details coming soon!

Lee Miller
Follow on Twitter!  @muturfpath
Extension Turfgrass Pathologist
University of Missouri