Oak Wilt
For me, it is a case of too much of a good thing. I’m guilty. Over the years, I have planted, encouraged the planting, and recommended the planting of too many Live Oaks and Red Oaks. And you ask, “What can be wrong with planting too many Oaks?”
Oak wilt. That’s what is wrong with planting too many Live Oaks and Red Oaks. In my own small way, I have contributed to a local environment that fosters the spread and devastation that is oak wilt.
For many years, oaks have been the staple tree for local residential, commercial, and public landscapes—and for good reason. Live Oaks and Red Oaks are both native to north central Texas. Both are well adapted to our soils. They are tolerant of our weather extremes. Live Oaks provide us with green foliage throughout the gray days of winter and signal that spring is finally here when bright, new foliage emerges. Red Oaks, both the Shumard and Texas species, provide the bulk of our fall color. Their abundance of acorns supplies food for wildlife, and gives us something to complain about. Once established, both withstand our hottest summers and relentless droughts. And, they have relatively few serious insect or disease problems, until now.
Oak wilt changes everything. The arboreal bliss experienced by standing under one of these majestic trees is cut short by the concern of ever-pending oak wilt. I now look at existing landscapes with a different eye. A small inner voice that speaks to me says, “What would this place be without all the oaks?” I don’t like the answer.
Based on the research at Texas A&M University, nature spreads oak wilt to healthy trees two different ways. A small insect, the nitidulid beetle, transports fungal spores from an infected tree to a wound on a healthy tree; and, trees transport the fungus through grafted root systems. It is an attack by two fronts—by air and by land.
The attack by air is limited. The production of spores and their transmittal from one tree to another is limited by seasonal conditions. The broad window is simple to remember: Valentine’s Day until Independence Day. The more specific window for north central Texas is late February to early June. However, the real window is very weather dependent, and each year varies.
The attack by land takes place throughout the year. While root grafting may not be fully understood, it is real. Research is telling us that a tree’s root system may extend beyond its canopy more than twice what was once thought, making grafting root systems a common occurrence.
While to date, none of the oaks I am responsible for planting has oak wilt. I am fighting the odds. It is likely that will not always be the case.
Now that I know the reality of the day, what is my recommendation for planting Live Oaks and Red Oak? No more than one tree of three. That is enough. For me, that is enough of a good thing.