Ailments Plaguing Oak Trees

Aug 23, 2019

Although oak trees are uniquely suited to the Iowa climate and landscape, many suffer from a variety of ailments stemming from insects, fungal problems, and disease. 

On this Horticulture Day edition of Talk of Iowa, the director of the Insect and Plant Diagnostic Clinic at Iowa State University, Laura Iles, explains common effects of insects on oak trees. She says that after dry weather lace bugs can contribute to the yellowing of leaves. Lace bugs can be identified as black spots underneath yellow leaves, but Iles says it isn't a major concern and recommends not worrying.

Lina Rodriguez Salamanca, a plant pathologist and diagnotician at the Plant and Insect Diagnostic Clinic, discusses fungal problems affecting oak trees. She says she has seen a lot of Botryosphaeria Cankers, which cause the ends of branches to turn brown. According to Salamanca, there isn't much to do besides properly mulching and pruning the tree.

However, Salamanca recomends waiting until winter to cut branches to avoid the potentially fatal oak wilt disease.

"Beetles can move this disease and when you make a cut on an oak, beetle will be attracted to it," Salamanca says. "And so this beetle may have spores of a fungi on its body and will bring these spores to the tree."

Later on, Iowa State University Horticulture Specialist Richard Jauron answers questions from callers about the issues facing plants and trees in their lives.