Green Light on Lawns
If Weeds Could Talk IPM Indicator Weeds in Home Lawns By Mr. Ryan Adams, Extension Associate, Center for Integrated Pest Management, NC State and Dr. Danesha Seth Carley, Associate Professor, Department of Horticultural Science, NC State
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weeds have a story to tell. Their mere presence communicates valuable infor- mation on recent maintenance practices employed. Cultural practices that promote a healthy and dense turf stand are one of the most important and least recognized weed control tools. In fact, many
pest infestations are triggered by problems associated with upkeep including mowing height and regularity, irrigation timing and frequency, and fertilization (usually too much or too little). Improper practices can stress the turf, giving weeds a competitive edge. Although herbicides may seem like a simple solution to weed problems, killing the weeds with an herbicide only treats the symptom without identifying the underlying cause. In order to treat the cause of a weed infestation, it is important to consider prevention, mechanical and biological options, and cultural practices that encouraged weed establishment in the first place. We will take a look at common indicator weeds in North Carolina turf and unpack what their presence can tell you.
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Mowing is the most time consuming maintenance practice, and many aspects of mowing are misunderstood and in some cases, can be performed incorrectly. Because lawns often look attractive after mowing it is easy to assume that grass thrives on mowing. In reality, mowing is a very destructive process that injures the grass plant. Each mowing temporarily reduces root growth, decreases carbohydrate availability, increases water loss, and decreases water absorption by the roots. Therefore, it is important to minimize these stresses with sound mowing practices. Ideally, the decision to mow or not to mow should be based on the growth of the grass, rather than a set schedule. As a general rule, mow as often as needed so that no more than one-third of the total leaf area is removed in a single mowing. For example, a bermudagrass lawn at a height of two inches should be mowed when the grass reaches three inches. If you are seeing dog fennel, chicory, blackberry, and wild carrot, it is likely you are mowing too infrequently, since most of these weeds are removed with consistent mowing. Conversely, if you mow your lawn too frequently, you will increase the likelihood of several weeds such as annual bluegrass, moss, crabgrass, chickweed, and goosegrass.
March/April 2019
