Disease management covers very wide variety of topics and in this article, we only aim to give you a brief overview of disease management practices, integrated pest management techniques and a basic understanding of these general concepts. Please refer to the rest of The Shed for more detailed articles on soil preparation, disease identification, disease prevention, and specific disease management techniques.
Before discussing disease management practices, the turfgrass manager must set their pest threshold, or action threshold. This threshold determines the amount of disease symptoms or acceptance level of the pest that will be allowed by the manager. While the action threshold is the hands of the turfgrass manager, it is often decided by those who mainly use the turfgrass system, whether that be on a golf course, sports field, or home lawn.
Action thresholds vary from very little to no pests allowed on one spectrum, like that of a major golf tournament or professional sports field, down to an eco-friendly home lawn which may let nature take its course. Disease management practices vary depending on the intensity level of the action threshold, which may range from preventative control, to curative control, or even no control whatsoever.
Understanding some general integrated pest management (IPM) principles is critical when prevention or control of diseases in turfgrass is desired. A turfgrass manager must know the interactions that contribute to disease occurrence. The three primary factors that are required to cause disease are susceptible plants, favorable environments, and the pathogen. This is often referred to as the pest triangle.
When the pathogen for any given disease is present alongside a susceptible plant host in favorable environmental conditions, you will notice disease signs that lead to symptoms in the turfgrass shoots and/or roots. Diseases in turf can be caused by bacteria, fungi, viruses, nematodes, and a few others.
Pest prevention mostly revolves around manipulating or catering to the environment and susceptible plant hosts, or desired turfgrass. Preventing or manipulating the local environment to be counterproductive to pathogen development can be done through various cultural practices, some of which are more easily controlled than others. The most common environmental factors that favor diseases in turfgrass are temperature, moisture, light, and wind. An example of manipulating one of these factors would be improving soil structure through turfgrass cultural practices to better drain water, thus preventing excessive moisture, which is often a condition that is required or accelerates disease progression. Combining cultural practices to alter environmental conditions can effectively deter known regional pathogens for the turfgrass species present and is the backbone behind IPM strategies.
Another key part in reducing and preventing diseases involves selecting turfgrass species and specific cultivars bred to be tolerant or even resistant to major diseases.
Finally, manipulation of the pathogen itself completes the pest triangle. In terms of actual manipulation of the pathogens, there is very little to be done in most cases. Depending on the region and pathogen in question, it is likely that the pathogen is already present in the soil, either active or dormant. So, what can be done? For pathogens that aren’t uniformly widespread, turfgrass managers can take precautionary measures to prevent or at least limit the spread of pathogens. Some practices may involve adapting irrigation practices to prevent flooding or runoff, regularly cleaning off equipment after use, and collecting or bagging clippings when signals of disease are present.
As a seed company that invests heavily into research and development, it is one of our goals to provide our customers with products that can better withstand diseases. Less disease often leads to turf managers saving time and money, fewer pesticide applications, and a more sustainable turfgrass surface. By managing older varieties of turfgrass that aren’t as suited for today’s increased environmental stresses and disease pressures, turf managers will often have to invest more in pesticides or cultural practices to achieve the same level of turf quality. For those managers that already cover all their bases in the other parts of the pest triangle, these advanced genetics often push their turf quality to new levels. Having a strong and competitive turfgrass will better stand up to disease, and greatly reduce stress levels of a turfgrass manager.
Knowing the disease at hand - or to come - is vital for pest prevention and control. It would be reckless to blatantly apply pesticides without knowing the cause of the disease, not only for the environment, but for your wallet as well. Disease identification can be accomplished by collecting plant material for analysis and combined with information on environmental conditions present alongside the turfgrass host. Typically, expert turfgrass managers can narrow down the disease with environmental factors alone during the growing season, and confirm with visual identification of pathogen parts.
Scouting should become much easier with the skill of identifying disease in the field, as well as knowing which pests are common in your area specific to the time of year. Scouting can be done at any time by simply going out and walking around turfgrass areas, but time can be saved by truly understanding the pest triangle for each individual disease. Expert turf managers generally know when a pest outbreak can be expected, and plan for prevention or further scouting, depending on the type of action threshold. As the pest triangle has a lot to do with pest pressure, indicators such as temperature fluctuations, moisture variances, and reduction in light frequency and intensity can all be forecasted and used in an effective disease scouting program.
To approach the actual control of a disease, one must think back to their action threshold. We can assume that if you’re still reading by this point, you might have some interest in controlling diseases to some degree. While it is completely acceptable to let diseases unfold onto a turfgrass surface, some situations warrant the control of diseases. In any case, using pesticides in a preventative or curative manner is to be decided by the turfgrass manager, and ultimately dependent on their action threshold.
Most diseases concerning turfgrass health tend to be fungal based. In the world of fungicides, there are a few things to consider before applying chemical control. Fungicides can be categorized into contact and systemic types. Contact fungicides tend to be used in a preventative manner by protecting or shielding the turfgrass plant parts they come into contact with. Systemic fungicides are absorbed by the turfgrass plant in varying degrees, and by different plant parts depending on the type. There are also other products like phosphonates, which are fungicidal and may also provide fertility benefits.
Traditional fungicides can also be separated by groups, or modes of action, in a numerical system. This grouping of fungicides is done to help prevent fungicide resistance in pathogen populations, which is an increasing problem in certain areas of the turfgrass industry. Therefore, turfgrass managers should not only be accurate in disease identification, but fungicide selection as well. Fungicides are often not a long-term solution, but a short-term fix to other underlying environmental or turf host issues. Resistance begins to be a problem when chemical control is the primary solution for pests and diseases.
These topics only scratch the surface in the realm of disease management. Expert turf managers are knowledgeable in many areas within the discipline of turfgrass management. We at Barenbrug hope that this outline of topics surrounding disease management helps guide or excite further learning in the world of turfgrass and we hope you join us in our quest to enhance the green spaces around us in a sustainable way.
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