“The All-Consuming Fire”
Oak wilt and fire have many commonalities. As long as there is a continuous source of fuel – both fire and oak wilt continue to consume and destroy. The utter devastation of this pathogen haunts me. I see myself as a firefighter – I won’t permit this scourge to continue without a fight. What we have done to date has helped – but too little, a drop in the bucket at most. What is needed is a fresh view in order to gain new insights to better know this enemy and find ways to win this war. Surrender is not in the blood and history of this state. Texans do not surrender when faced by a powerful adversary, rather they cry, “remember the Alamo”!
As with the other sections, I will focus on the aspects not spoken of as much or at all, as well as directly take on the errors and deficiencies found in the other available oak wilt primer materials previously or currently available.
This fungal pathogen has two main means of spreading: by means of an insect vector carrying spores from a fungal mat to a fresh wound, and through connected root systems. While root spread enlarges an existing oak wilt mortality center, the vector method of spread is de facto the beginning of a completely new oak wilt mortality center. Numerous northern experts have opined that this disease is very inefficient and precarious in its means to maintain its existence – but the reality of the Texas situation does not reflect that at all. Our losses are catastrophic and the situation is becoming even more dire. It is unreasonable to expect different results if we maintain the status quo.
Overland Spread of Oak Wilt (Long Distance)
Spanish Red Oak "on fire" with Oak Wilt
Mycelial mats or more often called fungal mats, spore mats or pressure or cushion pads, is the reproductive or saprophytic phase of this fungus. I concur with the Texas Forest Service that here in Texas the sporulation phase occurs only in the red oak species. An as-yet unspoken qualification must be proposed though: the Bur Oak up north, according to Jennifer Juzwik, often forms viable spore mats. Will the Bur Oaks planted here also produce fungal pads? This must be studied intentionally through deliberate, controlled, inoculations. One thing I don’t agree with the Texas Forest Service regarding spread is the position that, “fungal mats form…in spring…for only a few weeks” (www.texasoakwilt.tfs.tamu.edu). The original version of the TFS website actually recognizes the formation of fungal mats in the fall as well. (Click on screenshot link below)
Why do I disagree? This is just another example of over-generalizations that, without a doubt are pedagogically damaging. What would be true is that in Texas a SP may form staggered fungal mats from fall, through winter as well as in the spring, which may stagger into the Summer. I do acknowledge that beetle activity is highest during spring, but there is a Nitidulid study that confirms they do not “fly north for the summer or south for the winter.” This study shows that beetle activity goes up and down but does not cease. What would appear to be a contradiction in position vs. protocol - one of the strong recommendations by the TFS is to paint all oak wounds and to do so all year long!
Further, they say not to prune between February 1st and June 30th – but if we followed that and completely abstained from pruning during that time frame, then we would be past spring and the proposed TFS “few weeks” deadline of viable fungal mat season – so why paint at all!?! What is actually true is that fungal mats can and do form all year long – thus the need to always paint. Summer mats are the least likely to occur and remain viable the briefest time period because of three principle reasons: heat, lack of water, and maybe most especially, that hypoxylon canker often wins the battle over sporulation territory during that season (here is one instance where the inefficiencies and weaknesses pointed out by northern experts and alluded to above is evidenced). Active summer mats will most likely be found much lower on the trunks while Spring mats can begin much higher (6” or greater DBH tree parts to the ground level). Inactive mats can be found by an experienced pressure pad hunter years after the fact.
Northern Fungal Mats
In this image, you can see where one fungal mat ages to black and another new fresh white one forms. The Oak Wilt Fungus is a virulent sporator. Prolonged, staggered mat activity is the norm.
Above images and videos are courtesy of Phillip Kurzeja
Texas Fungal Mats
WINTER Fungal Mats
FALL Fungal Mats
SPRING Fungal Mats
SUMMER Fungal Mats
Here is a very interesting quote from the USDA Forest Service Northern Division (in a peer-reviewed and re-printed 2017 guide intended for a national audience):
Spore mats can form only within a year after tree death and only when air temperature and wood moisture are within a certain range. In the Northern United States, this combination of wood moisture and temperature commonly occurs in the spring of the year after the tree dies, or sometimes in autumn of the year the tree dies. As latitude decreases, the period of time during which mats form increases. In Texas, mats form at any time during the year, but most commonly in late fall and winter when the weather is cooler and wetter. In addition, spore mats are formed only on [red oak species] and never on Live Oaks…Spore mats usually do not form on trees smaller than [6” DBH]…Across the range of oak wilt, most spore mats are produced on trees in the red oak group, but mats can also develop on the Bur Oak. Mats do not form on other trees in the white oak group.”
I would love to hear the TFS response to the information contained both in this quote and my experience and position stated prior to.
Nitidulidae Beetle
The Nitidulid or “picnic beetle” is a sap-feeder. The aroma or volatile or pheromones released by the fungal mats is strong enough for us to smell (some describe as: fermenting apple cider, juicy fruit gum, rotting melons, and good vanilla ale) – for a beetle, it is like an extremely loud dinner bell. After carousing all over the pressure pad, the beetle, covered in virulent spores, heads off to find its next buffet and unknowing deposits “death to beech” in a yet uncured and un-painted wound on a member of the Beech family. How do I know the wound is unpainted? Fact: Nitidulid beetles do NOT find the smell of latex paint in any way shape or form appealing. They will undoubtedly steer clear of the over-powering and noxious smell. Color has nothing to do with it either. Clear or amber sap-colored paint will work just as good. Whether it is dripping thick coverage or a light dusting isn’t of consequence either – it is NOT the barrier component of paint that wards away the beetle – it’s the smell.
Most painted wounds will cure in enough time for both the smell duration and the curing time frame to coincide. The paint barrier after the wood is cured (or if the wood “wound” was deadwood to begin with) IS OF NO VALUE. Communication of infection is always, 100% impossible if wound tissue is dead/cured. Studies show beetle activity is higher in the spring. Studies ALSO show that the beetle does not hibernate like a bear in Texas between June through January. They are even active in 30-40 Fahrenheit weather in central Texas. The Nitidulid beetles unintentionally effect new oak wilt centers all year long. One of the most serious hindrances to more effective control of new oak wilt centers occurring from human activity is the public message campaigns that more often than not lead property owners to a false sense of safety outside of spring months. These beetles do not fly far. They are tiny. You need a magnifying glass to see their anatomy. They can and do land on moving objects like animals or vehicles and travel far that way. By long-distance spread though, we are mostly referencing spread by red oak group ONLY infected logs or firewood traveling long distances with developed viable spore pads or spore mats in process of formation.
Oak Wounds
Finally, we have fungal mats and a vector but we need a wounded oak. The TFS points out that there is a direct correlation between human population density and new oak wilt centers. That is spot-on accurate. We are a major impetus to wounds on oaks. BUT, there are many natural kinds of wounds that ALSO occur frequently and combined together – I believe accounts for as much or more total wounds on oaks than those caused by humans. For example:
- Animal damage (deer, porcupine, squirrel, horses, etc.)
- Branch breaks/trees falling over (wind or “sudden limb failure”)
- Rubbing branches
- Lightning damage
- Freeze/ice damage (yes, and BTW winter wounds take a considerably longer time to cure than the other 3 seasons)
Oak wounds, contrary to what many may think, often cure within hours. Except for major trunks fracturing or splintering, which may take a day or two to fully cure – the time of infection is not long. That is why wounds must be painted promptly. Natural tree curing and wound response is best and fastest in the springtime, with summer second, Fall third and the worst response time and healing capacity is from winter wounding.
Underland Spread of Oak Wilt (Local Spread)
In Texas, tree for tree – annual numbers of trees infected from spore transfer vs. tree to tree via root transference, are nowhere near equivocal. Root transfer in my professional assessment is likely responsible for 90-95% of new infections. My percentage is higher than the TFS estimates because they do not have an accurate, real-world understanding quite yet of the normative inter-species (between species) transfers occurring and the acknowledgement of the large-scale mortality of white oak species occurring as a result of oak wilt, which they are wrongly attributing to drought, hypoxolon canker, or unknown causes. The TFS makes a distinction between interconnected roots vs. grafted roots, which interconnected roots are associated with oak species that often expand the mott through root sprouts that grow into trees and characterized by a long-established foundation of roots. The TFS rightly says that this is the normative existence of the Live Oak species but then says the Shin and Lacey Oaks only “sometimes” form similar root systems. This is grossly incorrect.
The Shin and Lacey Oaks are genetically geared to form the exact same kind of mott expansion through roots sprouts off interconnected root systems as do Live Oaks. The other root connections the TFS calls grafted roots, where they make the very unfortunate and erroneous statement that these grafts between species are: only “occasional”, slower to transfer, and only over shorter distances. I have compiled a significant number of videos (see my YouTube link at bottom of the page for full collection – some of which are on the website) that show the exact opposite. These videos represent what I see every day at my jobs where I manage oak wilt over thousands of acres across central Texas and what I see on tens of thousands of acres in my drives to and from those jobs. They are not cherry-picked videos, they accurately show what I see ad nauseum. At most – rarely are these grafted root transfers slower, less numerous, and shorter. REGARDLESS, THE RESULTS ARE THE SAME – TRANSFERENCE AND LIKELY FULL MORTALITY WILL OCCUR (one exception: though I have reasons to believe the Post Oak often survives infection – I am unsure if they graft with each other or with other oaks as frequently as the other oak species do - I hope more research will occur to determine that).
Case in point - I am a member of the International Oak Society, and in their Newsletter (Oak News & Notes, summer edition, 2009, pgs. 1, 6), there was a story about oak wilt transference from a hybridized red oak species to two non-indigenous white oak species at the Starhill Forest Arboretum – known for its amazing and invaluable array of oak species from all over the world. In Mr. Guy Sternberg’s document titled: “Managing Oak Wilt” (International Oaks, Issue No. 30, 2019 ISSSN 1941-2061, pps. 209-216), he provides an excellent more in-depth reprisal than the newsletter referenced above of both what they experienced during the two separate infection events as well as a perfect exposition of prompt, precise and effective eradication of the offending pathogen. Of particular note, he adds to what we learned from the European white oak species susceptibility study showing high mortality rates when assumed otherwise, that there is a high likelihood of mature oaks forming root connections regardless of species. He recounts in the first 2008 infection, with numerous species - taxonomically two subgenera and three sections (Lobatae, Cerris, Quercus) were included in the root transference – species represented: a hybrid Northern Pin/Red Oak, Southern Red Oak (both Lobotae red oak species), a Chinese Cork Oak (Cerris) and Mongolian Oak (Quercus). In the 2012 infection, he identifies the Strandzha Oak (Quercus), Spanish Red Oak (Lobatae), Persian Oak (Quercus), Liaotung Oak (Quercus), Jolcham Oak (Quercus), and a hybrid Sessile/English Oak (Quercus) as all exchanging the fungus via root grafts (again a very surprising spectrum of subgenera and sections of oaks from numerous continents). I am even more convinced that we must abandon our prior erroneous assumptions for the conviction that, regardless of species oaks will likely give and acquire the disease from one another if within typical root system expanse of each other.
The devastation of this disease – the reason it is has reached epidemic levels in Texas is also due to human activity. All of central Texas is in most cases completely connected by oak roots because we have disallowed natural and intentional fire-restoration to occur and have failed to provide a substitute means to obtain the effects of mott separation, which fire regularly provided. There is a way to accomplish this. We will look into that more in the management section that will be forthcoming. Finally, a word to re-grafting of severed roots. The genetic makeup of oaks is clearly to function as a community. When their roots are temporarily severed – say through a barrier trench, the response of oaks is to re-unify in haste. I often see new oak root sprouts form like a cornrow in trenches in less than 6 months, where the new sprout is hastily feeding the regrowth of the damaged roots with the end goal of reunification.
We will discuss this further in management, but I will close out this section with a quote from Dan Wilson with the US Forest Service Southern Research Station, taken from his presentation during the 2007 Second National Oak Wilt Symposium:
Most oak wilt specialists acknowledge that the formation of new root grafts across an oak wilt suppression trench may eventually occur, leading to a breakout some years after a trench is installed. In the author’s opinion, this phenomenon is not only common, but increasingly prevalent three years after trenching, even in dry sites, especially for Live Oaks that have such a strong propensity to form root grafts in the shallow soils of central Texas. Oak roots in this region on the Edwards Plateau commonly grow through layers of limestone permeated by pockets of soil. Soil usually fills holes in the rock formed by the percolation of groundwater through the limestone. Nevertheless, the limestone rock bed layer tends to restrict and concentrate oak root growth above it, increasing the chances for root graft formation between the roots. In this situation, trenches alone are not intended to provide long term protection against root transmission because new root grafts are expected to form over time between these concentrated roots that grow within trench backfill soil” (pgs. 211-12).
View the inter-species grafting videos below or watch the full playlist on Youtube.
