Now Is The Time To Prevent Winter Annual Weeds

By Todd Lowe, Senior Agronomist
September 14, 2011

 Poa annua is a prolific seed producer, and heavy infestations can build on both overseeded and non overseeded Florida fairways.  The late summer and early fall are when control measures need to undertaken.  In this image, a control application was applied on the left.


Weeds are a concern on all golf courses, and are particularly important in Florida where warm, humid conditions encourage seed germination and rapid weed growth.  Consequently, golf courses throughout the region spend a considerable amount of time and money to control weeds and produce fine turf playing conditions throughout the year. 


During the fall, winter and spring, Poa annua is a particularly troublesome weed.  Poa annua is genetically diverse and produces an abundance of seeds each year.  These seeds have a broad germination window and can germinate from late summer into early winter.  Some Florida golf courses overseed with perennial ryegrass to improve color, but this also increases Poa annua populations.  Since both perennial ryegrass and Poa annua are cool-season grasses, it is difficult to apply herbicides to control Poa annua without harming perennial ryegrass.  Dr. Bert McCarty, Clemson University, reported several effective strategies for controlling Poa annua in both overseeded and non-overseeded bermudagrass in a previously recorded USGA webcast.  View this recording for free at: 


Dinitroaniline (DNA) herbicides like pendimethalin or prodiamine have become less effective on Poa annua due to repeated use and development of resistance.  Applying herbicides of the same family or mode of action for multiple years greatly increases the likelihood of herbicide resistance.  Golf course superintendents have remarked about reduced Poa annua control on TAS visits, and herbicide resistance on Poa annua has been reported for ten different herbicides used on golf courses 


Specticle (indaziflam) is a new pre-emergent herbicide for southern golf courses that became available in Florida in the early spring of this year.  Specticle is from a herbicide family that is different than other pre-emergence herbicides and can be rotated with other materials to reduce the likelihood of resistance.  Slight injury occurred on several Florida golf courses following Specticle application this past spring, and the product was re-formulated and a reduced rate placed on the label.  Also, seashore paspalum was removed from the label.  


Source:  Todd Lowe, or 941-828-2625 


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