Weed Control in Fine Fescue Naturalized Areas

Key Takeaways

• Weeds will always be a challenge in fine fescue naturalized areas. The level of resources required to manage weeds depends on expectations and natural factors like soil type and rainfall.
• Expectations must be clearly defined to develop a weed management program that delivers the desired results.
• Maintaining thin, wispy fine fescue naturalized areas with minimal weed encroachment often requires a significant investment and may cost more per acre than maintained rough.
• Properly timing mowing, collecting clippings, and applying both pre and postemergence herbicides is critical for controlling weeds, but some breakthrough is still going to occur.
• Selective mowing and spot treating weeds can help address problem areas that arise during the season. Some areas will likely require more attention than others based on visibility and proximity to play.
  
   

Mowing

Before taking a deep dive into herbicides used for weed control, it is important to understand the role of mowing. Not only is mowing an effective form of weed control in its own right, most herbicide applications will also be planned around the mowing schedule. Generally speaking, fine fescue naturalized areas are mowed at least once in the spring and once in the fall. However, additional mowing may be necessary depending on conditions.

Investing in equipment that makes it possible to mow these areas and collect clippings is money well spent. Being able to process the clippings improves playability because a dense mat layer does not form, and overly dense turf can be thinned by mowing more aggressively. Collecting clippings also improves postemergence herbicide effectiveness because weeds are not covered by clippings and preemergence herbicides can be moved into the soil more easily to create a barrier against weeds.

Spring mowing will have a significant impact on density and weeds. Mowing later in the spring will reduce density and weed encroachment, but it also decreases the amount of seedheads. If the goal is to have more seedheads for aesthetic reasons, mowing should be completed earlier in the spring, but there will be a trade-off in weed management. It never hurts to set up test plots that are out of sight to evaluate how mowing at different times in the spring impacts seedhead production, density and weed pressure to more accurately determine when mowing should be performed.

Fall mowing begins the process to prepare for next season. Provided weed encroachment was not an issue, there is some flexibility on when mowing can be performed. Enough time should be allowed for all the areas to be mowed and to apply both postemergence grassy weed and broadleaf weed herbicides when conditions are favorable. Every golf season is different and there will certainly be situations where even with the most detailed weed control program, breakthrough occurs. It may be necessary to mow earlier than expected so weed encroachment can be controlled.

It is important to recognize that mowing to control weeds in fine fescue naturalized areas does not have to be an all-or-nothing proposition. Many courses selectively mow certain fine fescue areas at greater frequency depending on weed issues, visibility, and proximity to play. If you start to develop a weed problem in a key area, a mid-season visit with a mower will go a long way. You will lose the remaining seedheads, but you’ll also knock back the weeds and make it easier for golfers to find and play shots.

Controlled burning during the offseason is another strategy that is used at some facilities as a form of “mowing.” Burning helps control weeds and reduces the accumulation of a dense mat layer. In certain environments, controlled burning may promote certain desirable plants while reducing weed pressure. Controlled burns are not permitted everywhere, and it is necessary to work with local authorities to determine if this strategy can be implemented.

Herbicide Selection and Timing

We’ve all heard the saying “An ounce of prevention is worth a pound of cure.” This is certainly the case when it comes to using preemergence herbicides for weed control in fine fescue areas. Prodiamine or pendimethalin are two commonly used preemergence herbicides that are typically applied once in late winter or early spring. These products will help control many broadleaf and grassy weeds. For improved weed control, it is worth considering a late summer or early fall preemergence herbicide application in addition to one in the late winter or spring. For improved broadleaf weed control, a spring application of the preemergence herbicide isoxaben can be included. The specific timing of these applications depends on a golf course’s location and weather conditions.

Preemergence herbicides are certainly a successful weed control program’s foundation, but breakthrough will still occur every year. Postemergence herbicides will be needed to control both grassy and broadleaf weeds that germinate throughout the golf season. Generally speaking, a broad-spectrum combination herbicide will do the trick for controlling most broadleaf weeds in fine fescue naturalized areas. Some of these combination products are also effective against troublesome sedges. 

Applying herbicides for broadleaf weed control in the fall should be a top priority because applications at this time of year provide the most effective control. This application should be made after mowing is completed but before temperatures drop and weeds stop growing. Additionally, a spring application of a broadleaf herbicide should be made to control any weeds that emerge in the late winter or early spring.

In addition to using a traditional combination product for broadleaf weed control, NativeKlean (aminopyralid and 2,4-D) can be applied for extended weed control. Applications can be made in the spring or fall depending on the weeds that are being targeted. Be sure to read the label thoroughly, especially as it relates to use limits and applications in proximity to trees. For grassy weed control, fluazifop and sethoxydim are the go-to products. Pinoxaden is another herbicide that can be useful for grassy weed control, especially if the goal is to suppress older tall fescue varieties, like ‘K-31’. Using both fluazifop and sethoxydim, where one herbicide is applied once in the spring and the other in the fall, will suppress grassy weeds. The key to controlling grassy weeds is to remain committed to the program.

When using the herbicides fluazifop, sethoxydim and pinoxaden, it is important for applications to be precise. If these herbicides are applied to nontarget areas that are not comprised of fine fescue, turf injury or loss will occur. Additionally, it is important to be realistic about what percentage of fine fescue is actually present in your target areas. If large populations of grasses other than fine fescue have gained a foothold, be aware that using these grassy weed herbicides will likely result in bare areas that require seeding. If the goal is to thin out areas and create an opportunity to establish more fine fescue, using these herbicides is a good option.

Be careful about mixing these grassy weed herbicides with herbicides targeting broadleaf weeds. An antagonistic effect will result if any of the three grassy weed herbicides mentioned above are mixed with a broadleaf herbicide containing MCPA or 2,4-D. As with all herbicides, always check the product labels and make separate applications if necessary.

Expectations will be the determining factor for in-season weed control applications. Tactics will vary based on the season and what works at your facility. Some superintendents find that using string trimmers is effective to keep weeds out of sight and out of mind until fall herbicide applications are made. Another approach is to spot treat weeds with backpack sprayers. With spot applications, a nonselective herbicide or herbicides specifically targeting the weeds that have encroached are viable options. Again, it is about figuring out what strategy meets your needs. The products discussed in this article that are used for weed control in fine fescue naturalized areas are summarized in Table 1 and are an important part of a successful strategy.

To cover all the herbicide combinations that could be used for a successful weed control program would be an entire article unto itself. Adjusting application timing and selecting herbicides that control the weeds of greatest concern at your facility is what’s most important.

If you struggle with controlling certain weeds, you are not alone. Some of the weeds that are most problematic in fine fescue naturalized areas include yellow nutsedge, thistles, unwanted turfgrasses, American burnweed, deer-tongue grass and yellow foxtail. For difficult-to-control weeds like reed canary grass and deer-tongue grass, spot treating with a nonselective herbicide is often the best option.

Different Programs for Different Expectations

The expectations that are set will ultimately determine the weed control program needed to be successful. If the goal is to conserve resources in fine fescue naturalized areas, they can be mowed once or twice a year and no herbicides would be applied. Under this kind of program, it is likely that weeds will take over and impact playability and appearance. With that being said, if the goal is to truly conserve resources, the exact plant composition of naturalized areas shouldn’t matter as much. Simply suspending maintenance, other than mowing once or twice a year, and letting the existing turf grow up in the areas that have been identified will achieve resource savings.

Assuming mowing is performed twice a year, clippings are removed, and no herbicides are applied, I estimate typical maintenance costs would be approximately $100 per acre. This is a significant savings when compared to the $1,500 or more per acre typically allocated to maintaining rough.

At most facilities, some amount of weed control beyond mowing is necessary to meet expectations for fine fescue naturalized areas. A program that controls weed encroachment adequately and manages density without requiring frequent maintenance throughout the season would be in the ballpark of what it costs to maintain these areas as rough. This would include mowing and collecting clippings in the spring and fall, preemergence herbicide applications in the late winter or early spring, postemergence herbicide applications for broadleaf and grassy weeds, and some in-season weed control in the form of physical removal or spot herbicide applications.

Producing thin, wispy and playable fine fescue naturalized areas where weed encroachment is minimal and golfers can locate and advance their ball relatively easily will result in higher maintenance costs than the two previously discussed programs. The costs can be highly variable depending on weather, soil types and how much time must be dedicated to maintenance throughout the golf season. It would be necessary to mow and collect clippings twice a year, apply preemergence herbicides in the late winter and/or early spring, apply postemergence herbicides for grassy and broadleaf weeds, and a significant amount of time would need to be dedicated to in-season selective weed control.

Weed control during the golf season – both physical removal and spot herbicide applications – could have to be completed as frequently as every week or every other week to keep weeds at an absolute minimum. Dedicating this level of maintenance to weed control will result in a dramatic increase in costs.

It is possible that delivering thin, wispy and playable fine fescue naturalized areas with minimal weed encroachment will cost more than maintained rough on a per acre basis, especially when soil physical properties are not ideal and frequent rainfall is experienced. Costs can increase even more if there is a need to address infrastructure issues contributing to weed encroachment and excessive turf density, like moving irrigation heads so they don’t throw into the naturalized area. You may conserve resources such as water, fuel and fertilizer – all positive impacts – but the additional cost of labor and herbicides must be recognized.

Additional Considerations

Like any playing surface on a golf course, water management influences conditions in fine fescue naturalized areas. Outside of establishment, these areas should not be irrigated. If irrigation coverage from the rough reaches the fine fescue, sprinklers or mowing lines should be adjusted to address the issue. Failing to control irrigation will increase density and weed encroachment, often in areas that are more likely to come into play because they are alongside the maintained rough. It is not uncommon for fine fescue areas to be overgrown closest to the line of play and progressively thinner as you get farther away. This is usually because of irrigation overspray.

Density and weed encroachment will be a greater challenge in areas where water tends to collect, especially for golf courses that receive modest to abundant rainfall. Installing drainage will create an outlet to remove excess water and reduce the likelihood of weed encroachment and overly dense turf.

Insects, mainly chinch bugs and white grubs, can also be a nuisance in fine fescue naturalized areas. Thinning caused by insect feeding can create an increased opportunity for weed encroachment and in severe situations reestablishment may be necessary. If insect feeding is an issue, treating with insecticides like imidacloprid, clothianidin or chlorantraniliprole will help address the problem. With imidacloprid and clothianidin both being Group 4A insecticides, it would be prudent to explore options in other classifications as well to help manage resistance and improve control.

Establishing plants like milkweed to attract monarch butterflies or wildflowers like aster to attract pollinators is often incorporated into fine fescue naturalized areas for the environmental benefit. If this decision is made, these areas will have to be treated differently from a weed control standpoint. It is best for these areas to be established in out-of-play areas, so a separate program can be put in place and playability is not impacted. The Green Section Record article, “Practical Pollinator Programs”, is a good place to get started if this is being discussed at your facility.

Summary

Weed control is a major component of successful management in fine fescue naturalized areas and must be tailored to the needs of your particular golf course. Timing mowing and herbicide applications to optimize weed management and selecting herbicides to control specific weeds of concern are key to delivering conditions that meet expectations. And remember, the label is always the law when it comes to making these applications.

Even with the most detailed management program, some weed breakthrough will occur every year. Ultimately, Mother Nature will determine what level of breakthrough is experienced and having clearly defined expectations will determine what maintenance practices are required. Every year is going to be different, but a few golfers grumbling about fine fescue naturalized areas is to be expected. When these situations arise, it’s important to bring the conversation back to expectations, costs and the natural factors that are beyond anyone’s control. Most courses are better off focusing their resources on primary playing areas rather than fine fescue areas at the margins, but that can be hard for golfers to remember after missing a fairway by 40 yards.