SportsTurf provides current, practical and technical content on issues relevant to sports turf managers, including facilities managers. Most readers are athletic field managers from the professional level through parks and recreation, universities.
Issue link: https://read.dmtmag.com/i/251524
18 SportsTurf | February 2014 www.sportsturfonline.com Field Science ble). These herbicides do not prevent weed seed germination; rather they prevent germinated seedlings from developing into mature plants. Con- sidering that the time- frame between weed seed germination and weed emergence can be quite short, it is often recommended that PRE herbicides be applied once soil tem- peratures are favorable for crabgrass seed ger- mination. Athletic field managers should make their first PRE herbicide application as soon as soil temperatures (at approximately 2 inches) measure ≥ 55°F for a minimum of 3 days in spring. Researchers studied how the blooming of 74 different orna- mental plants in spring corresponded with the emergence of crab- grass in turf. They concluded that blooming of border forsythias is a helpful indicator of when to apply PRE herbicides for crabgrass control. Border forsythias produces distinctive yellow blooms at soil temperatures similar to those that facilitate crabgrass seed ger- mination and emergence. Thus, athletic field managers should be sure to apply PRE herbicides before forsythia plants have com- pleted flowering each spring. #2- Irrigation: A key to effectively controlling weeds with PRE herbicides is to water them into the soil after application. Most labels require that 0.25 to 0.50 inches of irrigation or rain- fall be applied within 24 to 48 hours after application. These her- Left: Figure 1. Effect of simulated traffic on weed encroachment into hybrid bermudagrass in Knoxville, TN during 2013. Right: Figure 2. Effect of PRE herbicide treatments in spring on hybrid bermudagrass cover after being subjected to simulated traffic events in fall in Knoxville, TN in 2012 and 2013. Data were combined to present the effects of single and sequential application regimes at the rates tested in both years. Standard error bars presented as a means of statistical comparison. Newly germinated crabgrass in the spring of the year. Forsythia is in full bloom. The yellow petal drop has not started. Photos and figure courtesy of Jeff Borger, Penn State Forsythia yellow pedal drop has begun. About this time crabgrass will start to germinate. A visual representation of the preemergence her- bicide concentrations in the top ¼ inch of the soil pro- file following an application in the spring of the year. Crabgrass plant's developmental stages