Symptoms of Oak Wilt in the Red Oak Family

Spanish Red Oak Symptoms

Quercus buckleyi

Many of the native Red Oaks in the hill country are a mostly-pure Spanish Red Oak strain. I sometimes see some traces of Texana in them and more curiously – I often see Black Jack cross-pollination (or vice versa) when these two in close proximity to each other. The Spanish Red Oak is without a doubt the second most prevalent native oak species.

It is very unfortunate that more effort is not being made to help train property owners to find and destroy red oaks with wilt. Beetles and paint is a moot point if sporulation of the red oaks isn’t allowed to occur due to a pro-active response. I believe that significant effort in this one specific task would have one of the most powerful impacts on disease management and must become a major focus of efforts from here on out.

In many cases there are not many fungal mats at any given time on any given 1000 acres, rather more likely 10-20, which is a manageable task to monitor and remedy. Further, studies done in other states give us a reasonable belief that either the use of fungicide or herbicide can prevent sporulation without labor-intensive tree removal and destruction (burn, mulch). Red Oak routinely pass the fungus to trees within grafting distance. They are often grafted with other oaks.

Oak Wilt Pictures: Spanish Red Oak

Spanish Red Oak Wilt Symptoms in the Central Texas Region 2

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Shumard Red Oak Symptoms

Quercus shumardii

Another non-native red oak – this one is actually one of my favorite oaks to plant if conditions are appropriate. Its quite a challenge for even a BCMA to find a pure specimen in most of these nurseries – more often than not it too is a “mutt tree” most often with texana genes mixed in.

When planted in oak wilt mortality centers – expect grafting once they have an established root system (6-8” DBH or more). I see it regularly. One property in particular – a 14” Mexican White Oak (AKA Monterrey Oak) contracted oak wilt and died not far from the Shumard. In my estimation, it was most probably that the Shumard acquired the disease by grafting and most probably from the Mexican White Oak. These two trees are more often than not grouped together in landscape installations…

Oak Wilt on a Shumard Red Oak in the Central Texas Region

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Black Jack Oak Symptoms

Quercus marilandica

The good tree with the cute duck feet-shaped leaves. The bad tree that possibly forms pressure pad fungal mats more consistently that Red Oaks. The ugly in that they are rare and many people are unaware how to identify them and therefore unable to proactively monitor them for possible contagion.

Northern Red Oak Symptoms

Quercus rubra

THE oak wilt oak - The one most studied in regards to oak wilt. The vast majority of losses in the Non-Texas states belong to this species.

Not only does regular root-grafting or (underland spread) occur but this species also forms fungal mats regularly and new infections by spore-carrying vectors occur often (overland spread). Mortality is very swift and frightening to those who lose numerous trees seemingly overnight. Often plowing or trenching isn’t an option for various reasons. The good news – herbicide containment works! More on that later…