Oak Wilt - What to do

Jon Ipema • June 16, 2023

Our majestic oaks are under attack!

Oak wilt is a fungal disease, not like the invasive bugs like the infamous emerald ash borer. This fungus was first noted in the 1940's, and has since spread to many areas across the United States. The fungus effects the uptake of water and nutrients to the canopy of the tree, effectively killing it in a very short amount of time.

Oak wilt can be transported by several insects, but it isn't the insect that is doing the damage. Instead, it is simply transporting the fungal spores to other trees. From there, the fungus can spread through root grafts (tree roots of separate trees that are interconnected). This is why it is not uncommon to see trees infected in groups. The two major groups of oaks are red and white. Red oaks form the fungal mat (pictured above), which insects are attracted to, feed on, and pick up the fungal spores. They then go to other oaks spreading the infection. Red oaks can die very quickly once infected often within weeks of infection. White oaks do not form the fungal mat, allowing them to survive longer. This has given the misperception that white oaks are resistant to this disease, they are not. Symptoms on white oaks include large portions of the trees dying without notice, eventually the entire tree will succumb to the fungal disease.

Symptoms of oak wilt include: wilting of leaves (hence the name), leaves turning fall colors unseasonably, half dead leaves with a distinct line between live and dead, and die back in the canopy. Red oaks may also show signs of the fungal mat, typically this is found underneath loose bark.

The best action is to be proactive. Prevention is far more effective than therapeutic treatment. The treatment consists of a fungicide injected into the tree. Healthy trees will uptake and spread the fungicide far better than infected trees. Once symptoms show, the likelihood of successful treatment diminishes rapidly. If you have oak trees that you cherish or don't want to pay the high cost of removal, it is best to act sooner than later.

The Green Advantage's ISA certified arborists can help with this and all ornamental diseases. We are here to answer your questions, find solutions, and make honest assessments on how to move forward. We look forward to hearing from you.

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The Cycle

By Jon Ipema • September 12, 2025

The goal of this article is not to berate other professionals, instead it is to get a better understanding of how to get desired results while avoiding counterproductive measures that often impede progress, increase maintenance, and are detrimental to the goals of plant cultivation and land management. Often attention is applied strictly to climate and aesthetics. The decisions are typically made based on whether a plant is known to survive in a particular zone and results from successful cultivation (often photos of established plants). Although these are important issues, the results are often compromised by disregard to soil type, soil quality, maintenance requirements, desired results, and specific strengths and weaknesses of individual species and subspecies. Proper consideration to the process and costs of achieving desired outcomes can be oversimplified to the detriment of that outcome. Observing this time and again, a cycle has been noticed that seems to repeat itself. Analyzing this cycle has given insight on how to avoid this cycle and the frustration that goes along with it. Signs of this cycle are increases in maintenance, costs, and frustration while experiencing decreased aesthetics, plant health, and recurring issues. Here is an example: 1. A lawn does not appeal to its owner and steps are taken to improve the situation. 2. The first step is often to incorporate a fertilization program. 3. A generalized fertilization program is implemented, with the primary focus being macro-nutrients for turf and weed control. 4. Initially this seems productive and seems to be leading to satisfactory results especially in the beginning of the season, when temperatures are lower and natural irrigation is sufficient. 5. As the season progresses and temperatures increase the results seem to diminish. The color of the lawn appears fair at best, weeds become more of an issue, and general satisfaction declines. Watering is increased, chemical applications to control weeds are rendered, and some choose to increase fertilization to achieve what seemed to be improving results earlier in the season. 6. During midseason, temperatures are at extremes, and the focus gets shifted to irrigation, with some increase to the length of time for irrigation but mostly on the frequency. 7. As the end of summer approaches, nighttime temperatures decrease, while temperatures during the day still feel extreme. Turf appears to be recovering and looking better. Weeds continue to be an issue and additional weed control measures are often taken, usually spot treating as even selective herbicides can damage turf in the heat of the day. At this point fungal issues appear and many opt to apply fungicides to control the matter. 8. Some satisfaction with weed control seems to take place although grassy weeds remain persistent and fungal issues come and go. Overall, the turf seems better than previous seasons and staying on the course seems to be the correct action for the next season. 9. Year 2. In spring pre-emergent weed control is applied to keep grassy weeds controlled (primarily crabgrass). Patches of inconsistent turf seem to be taking hold, and the turf color continues to decline. Spring is often when other fungal issues are noticed, especially cold season fungal issues that take place throughout the winter (snow molds). 10. Increases in fertilizer are often recommended to return color to turf while weed control becomes a larger issue. Irrigation is more frequent, as it seemed to help the stressed turf during the previous season. 11. Although recommendations are followed, by midseason it is apparent that turf quality is not improving, there may be a noticeable “boost” to aesthetics for a short period after fertilization, but not much further. 12. When evening temperatures begin dropping but daytime temperatures are still high, fungal issues return. It may be recommended to add fungicidal applications to the fertilization program annually to “get ahead” of the problem. 13. Turf doesn’t seem to improve any further and is often declining at this point. During the 3rd season some owners begin looking at other options, but some stay on this course and continue, many of these individuals simply get accustomed to a subpar lawn. Others contemplate discontinuing service, as the programs appear to be a gimmick. 14. By the fourth season many have had enough. Many companies will continue to offer more services claiming that they will solve the issues. By this point the customers usually have had enough, even more convinced that their lawn will just never look the way they would like. This pattern is not absolute and some lawns with this type of program do have success. My experience is that these results vary from lawn to lawn, are not replicable, and lack consistency. This brings us to the main point of this article…How do we stop the cycle, get the results we want, without constantly increasing the need for more maintenance. Lets start at the same point as we did earlier. 1. A lawn does not appeal to its owner and steps are taken to improve the situation. 2. Soil tests are taken to provide information as to what is going on currently, how to adjust, and what type of grasses fit the purpose of the lawn. 3. Soil amendments are made to correct micro-nutrient deficiencies and correct soil chemistry. Aeration is completed to aid the microbial processes in the soil, reduce compaction, and maintain the thatch layer. Lawn is overseed with turfgrass that fits the desired outcome, thrives in the climate, and resists disease. 4. Fertilizer program is implemented to address macronutrients and help maintain chemical adjustments performed in previous step. At the beginning of this process, pre-emergent weed controls should be avoided and only implemented in the future if annual weeds are an issue. Even then I personally am not a proponent of preemergent weed control in turf, unless absolutely necessary as this hinders seed germination and causes issues with overseeding. 5. Instructions are given on maintenance information. Turfgrass needs to be maintained at a certain height and cut at regular intervals to maintain that height. Sharp blades and maintained equipment are important for turf grass health. This thick grass not only for aesthetic purposes, but also for weed control. 6. In spring when conditions are optimum for turf grass growth, the desired grass species will begin to take hold. As temps increase and are less favorable to the other grasses, this will become the dominant. With the corrections in the soil chemistry and condition this species will thrive, not allowing area for weeds to encroach. This is not to say weed control is not necessary, but it is drastically minimized. 7. Aeration needs to be performed on a regular basis, 1 to 2 times a year minimum, based on grass species, soil conditions, thatch conditions, and activities on the turf. 8. As the heat of the summer stresses the turf grass, correct watering is pertinent. Root systems of all plants require water, but they also require oxygen. A flooded root system will kill plants. Less frequent, deep watering is what plants including turf need. Turf grass varieties that are more tolerant of temperature extremes are the best solution to this issue. As these grasses grow and begin to dominate the turf ecosystem, other non-desirable plants will not have room to get a foot hold, limiting the need for weed control. Short frequent irrigation creates the environment for fungal disease. Without fungal disease the use of fungicide would be minimal if not irrelevant, avoiding the damage to mycorrhizae. These beneficial fungi aid in oxygen and nutrient transfer in root systems. 9. Year 2. Turf appearance drastically improves as does the health of the grasses. Soil amendments are not necessary unless problems exist. Soil test should be done regularly (I recommend every 3 years, unless issues are present). Aeration and overseed are recommended in spring and fall, continue to feed (general purpose fertilizer, 4 application slow release sulfur coated urea), and continue maintenance as described above. 10. Lastly, enjoy. Healthy plants resist disease. Working with nature, controlling what we can, and mitigating what we can’t is the answer to all turf and landscaping. Overall maintenance will be far less chaotic as the days of chasing symptoms will come to a close. Any issues that arise can be dealt with systematically.