NORFOLK, Neb. — It’s almost all bad news for trees in the Arbor Day state.
That was the key message delivered to a capacity crowd of tree lovers, professional arborists and nursery enthusiasts at the Lifelong Learning Center in Norfolk on Thursday.
Presenters from the Nebraska Forest Service and University of Nebraska Extension tried to lay the groundwork for mitigating some of the deadly ills facing trees in Nebraska.
Unprecedented drought conditions last year coupled with above-average temperatures means that the drier soil surrounding tree roots often is pulling moisture from the trees instead of the other way around, said tree scientist Graham Herbst.
When trees are stressed by drought and heat, especially the non-native varieties or ones that were improperly planted, they become much more susceptible to deadly pests and diseases such as pine wilt, which is devastating area conifers.
“I’d hate to be a tree in Nebraska,” quipped forester Justin Evertson.
He also engaged in some dark “tree-hugger humor” when he said there may be a silver lining to the drought: It’s about the only thing that has been able to kill invasive red cedars.
Tree loss also takes a human toll, said area forester Steve Rasmussen. He cited a recent study in a respected medical journal that correlated increases in human mortality rates due to cardiovascular and respiratory tract illnesses in U.S. counties where the emerald ash borer has killed a significant number of trees.
That emerald ash borer is poised to cross the Nebraska border from Kansas.
The stately green ash trees that dominate much of the urban landscape in Nebraska will go the way of American elm trees that fell victim to disease in the last century. It’s only a matter of time. Efforts to save the ash with pesticides will be prohibitively expensive in most cases, the tree experts said.
Citing state statistics that show a $35 billion negative impact on the state’s economy because of the drought, Herbst said the conditions are right for the loss of millions more trees if deep-soil moisture doesn’t improve. The danger is most serious for evergreens and non-native species.
So what should tree-loving Nebraska property owners do?
First, the foresters said, get expert advice from a certified arborist, forester or nursery professional. Conditions vary, and the wrong interventions can cause more harm than good.
For instance, they said, frequent shallow watering that benefits lawns is generally unhealthy for trees. Trees need deep-root moisture — more than 12 inches down — to survive drought. Shallow watering to keep lawns green means the trees develop shallower root systems.
Fertilizing is not recommended, especially for drought-stressed trees.
The most urgent action for all Nebraskans is probably to get busy planting new trees to replace those already lost.
But the foresters warned that only native varieties that are disease- and pest-resistant as well as drought-tolerant should be considered. They must be properly planted and nurtured in the first few years after planting. That means deep watering and professional advice even for do-it-yourselfers.