A New Approach
Don't mess with Mother Nature! How often have we heard that refrain? But do we actually walk the walk, or, more often, do we just talk the talk? When it comes to managing turfgrass pests, the importance of recognizing the influences of nature and working with them by integrating our management approaches cannot be emphasized enough. Over the past several years, our industry has been blessed with a plethora of chemicals for our pest management toolbox. These products are thoroughly tested for efficacy and safety. They are brought to a highly competitive market and introduced to us for what they can provide as a “controlling” tool.
Herbicides and plant growth regulators are tested by reputable weed management scientists; fungicides are tested by reputable plant pathologists; insecticides are tested by reputable entomologists. Ultimately, local use rates and recommendations are generated by the results of this testing process. However, the missing ingredient in the process is the evaluation of such products as to their interaction with other cultural management tactics, assessments of their threshold levels and how their efficacy and safety may be enhanced by combining them with other products that might be unrelated to pest management per se.
WEED MANAGEMENT EXAMPLE
Managing weeds in turfgrass situations is particularly demonstrative of how we can effectively work with Mother Nature. Weeds have been provided to us as a tool to assess how well we are managing the turf. After all, without a void in the turf, weeds would not have an opportunity to invade, and weeds are nature's consummate opportunists when it comes to occupying available space. Therefore, assuming the weed is properly identified as to individual species, the question must be asked, “What is it doing there?” Asking and answering that question is the beginning of working with Mother Nature in order to successfully manage weeds.
Certain weeds are terrific indicators of soil conditions and cultural system breakdowns, and these can reflect patterns of use (including abuse). Weeds, however, should only be considered as indicators when they are the predominate plants in an area. For example, knotweed and goosegrass both indicate compaction because they can maintain adequate root respiration at lower oxygen diffusion levels than other plants. You can easily control both of these weeds by applying either post- or pre-emergent herbicides. However, if the compaction problem is not resolved, the weed problem will be chronic and will, therefore, not go away. Only after you solve the compaction problems will the turf prevail. Further, by correcting the compaction problem, the efficacy of the herbicides you use will be enhanced due to the improved plant competition by the turfgrass. In the end, competition from knotweed and goosegrass will no longer be a chronic problem that requires repeated herbicide applications year after year. Not to say that, in some situations (where you cannot change traffic patterns for example), some level of herbicide application will not still be necessary from time to time. Other examples of when weeds are good indicators are: poor drainage (presence of sedges, annual bluegrass and creeping bentgrass), low nitrogen fertility (presence of legume species), low pH (presence of sheep sorrel), high pH (presence of common plantain) and insect problems (prostrate spurge, yellow wood sorrel), to name a few. For all of the above cited examples, there are management system inputs that you need to either change or introduce that will enhance turf competition before any herbicide — or other pest management chemical, for that matter — will have the desired impact.
At times, we encounter multiple pest problems simultaneously. The reasons for such occurrences are usually not too far removed from those that result in just one category of pest problems. Multiple pest problems often are linked to a breakdown in the cultural management system that is in place. Although such a statement may seem harsh, more often than not, it is true. Again, when such maladies occur, you must be introspective and carefully, honestly, evaluate your cultural inputs and how effectively or not they are integrated. Management inputs cannot be random: “Oh, I thought I might try this today.” Such an approach is doomed from the beginning. Proper integration of tools and tactics requires thought and planning. We must constantly challenge our viewpoints and approach in order to provide the turf with a chance to provide the best possible aesthetic quality and function. Thinking is the hardest part of any job, but the most necessary of all.
The problem with simultaneous multiple pest problems is the decision as to which one to attack first. Before that decision is made however, you must first answer that nagging question: Why is this happening to me? First and foremost, you must fix those cultural breakdowns that you can identify and then you can go to the next step. In that process, you must be sure to not over-use the age old excuse of “it was a bad stretch of weather.” Clearly, the weather does play a role in the severity of pest problems, but you can manage the degree to which it does. In the final analysis, the order of attack when multiple pest problems occur is to go after the one that is the most potentially devastating in the short term. Threshold levels of infestation vary from turf species to species and location to location on an individual property. Thus, any determination about threshold level is necessarily site specific and personalized. Threshold level guidelines provided by entomologists, pathologists and weed scientists are useful, but are not cast in stone. Each turf manager must make the individual call regarding appropriate threshold levels for his or her property. When all is said and done, managing multiple turfgrass pests is very subjective regarding tactical approaches and requires thoughtful decisions about how to “cut one's losses” and most effectively deal with the situation.
CULTURAL SYSTEM MANAGEMENT AND PRE-CONDITIONING
We must constantly evaluate our cultural maintenance practices to be sure that we are truly integrating them into a management strategy that will be successful. The gist is that a healthy, highly competitive stand of turf is the best defense against pest invasion of any kind. However, the best growing conditions are not always provided by nature, but rather how well prepared we are when adversity comes our way that translates into successful management. Another part of working with nature is to adopt the philosophy of “pre-conditioning.” Clearly, environmental stresses will occur every year. Unfortunately, in managing cool-season grasses, stresses often occur when the turf is intensively being used, mainly in the summer. Consequently, a “double-whammy” can occur whereby use and abuse are added to the environmental stress factors. This combination can render the turf even more vulnerable to pest attack or invasion. Thus pre-conditioning can, at least, provide some preemptive management approaches, that have the potential to reduce the magnitude of the pest problem once it occurs. Pre-conditioning approaches include proper rate and timing of nitrogen fertilization; use of minor nutrient packages, bio-stimulants and growth regulators to conserve carbohydrate reserves; good soil management through improved oxygen-water relationships and amendments; and proper irrigation practices to adequately provide moisture and reduce evapo-transpiration rates.
This listing of pre-conditioning practices sounds like a review of Turfgrass 101, which is probably true. However, in dealing with and trying to manage Mother Nature, you must constantly review the basics, apply integrated approaches, take inventory of what you are doing and keep in mind that she can be an ally, not always a protagonist.
Thomas L. Watschke, Ph.D., is professor of turfgrass science at The Pennsylvania State University (University Park, Pa.).
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