Get ready for the emergence of crabgrass
12 Apr, 2010 By: Karl Danneberger LM Direct!When the first warm days of spring arrive, a common point of turfgrass discussion is when will crabgrass appear. Crabgrass emergence is often associated with phenotypic events like flower withering of Forsythia or the initiation of flowering by dogwoods.
Watching for germination of crabgrass in cracks in pavement can serve as an early sign that crabgrass emergence in turf is not far off (although these early germinating plants are susceptible to cold and usually die with the arrival of a cold snap). Other crabgrass emergence keys are based on soil temperatures.
A key thing to keep in mind about soil temperature and germination: Pre-emergent herbicide applications should be made prior to minimum soil temperatures reaching around 55 degrees Fahrenheit to 59 F (13 degrees Celsius to 15 degrees C) at the 2.5-centimeter depth at daybreak for four to five days, in which crabgrass will germinate.
Phenotypic events also play a role in germination. Pre-emergent herbicide applications should be made 14-days prior to these phenotypic events:
• forsythia bloom withering (more applicable in Northern temperate regions);
• daffodil (Narcissus spp.) bloom withering; and
• dogwood (Cornus spp.) bloom withering (more applicable in warmer regions).
In regard to crabgrass emergence, the University of Maryland's Mike Fidanza, Ph.D., and Peter Dernoeden, Ph.D., proposed the following from their research on degree days for predicting smooth crabgrass emergence in cool-season turfgrasses:
• Average minimal soil temperature, in which initial appearance is observed: 54 degrees F.
• Average mean soil temperature, in which initial appearance is observed: 60 degrees to 64 degrees F.
• Average minimum soil temperature, in which major emergence occurs: 60 degrees to 70 degrees F.
• Average mean soil temperature, in which major emergence occurs: 73 degrees to 75 F.
Hope this information helps. Here's to keeping the crabgrass out of your golf course or sports fields.
Editor's note: "Puttin' Down Roots," a new e-newsletter from Golfdom magazine and sponsored by BASF, focuses on plant health.
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