Current Pests & Diseases
Emerald Ash Borer
Emerald Ash Borer (EAB) is an exotic invasive beetle from eastern Russia and northeastern Asia that likely was brought to the U.S. in infested packing material. This beetle threatens our urban and riparian forests by killing North American ash species (Fraxinus sp.) and their cultivars. Over 25 million ash trees have been destroyed due to EAB. Adults are usually present during the summer months (May-August) depending on the weather patterns. A few weeks after eggs are deposited in crevices in the bark they hatch and the larvae begin to chew through the outer bark to the phloem. When feeding they begin forming S-shaped galleries (July-October) that expand as they grow. This feeding disrupts the transport of water and nutrients within the tree. The larvae overwinter as prepupae in the sapwood and in the spring after a few weeks pupate and emerge as adults (May-June) creating a D-shaped exit hole. As adult beetles, they feed on the foliage during their 3-6 week lifespan, mate, and then the process begins again each year. Weather is a key player on timing for the beetle. For example: if it is a warmer than usual year then emergence and flight will occur earlier.
The disease pine wilt is caused by the pinewood nematode, Bursaphelenchus xylophilus, but unlike its counterparts is transmitted from tree to tree by an insect vector, the pine sawyer beetle, Monochamus carolinensis (a long-horn beetle). In Japan, pine wilt has caused severe mortality in the red and black pine forests. This disease occurs in the U.S. east of the Rocky Mountains, where known hosts grow. It was discovered in southeast Kansas in 1979. It is very common in the eastern half of the state and is slowly spreading westward.
Oak wilt is a lethal systemic disease caused by a fungal pathogen. This disease is found throughout the eastern and central U.S. as far as Texas. It is responsible for killing many landscape and forest trees. In the 1940’s it was first identified in Wisconsin. Since then, the number of incidences has fluctuated but it is still a slow and sporadic threat to local populations of oak trees. This disease is found more commonly in the eastern third of the state.
Dutch Elm Disease
At one time, American elm was the most planted tree in America because it was well suited for the urban environment as it is long-lived, fast growing, and tolerant of compacted soils and air pollution. Dutch Elm Disease (DED) entered the U.S. accidentally on elm logs shipped from France to Cleveland, Ohio, in 1931 and by the mid-1930’s the pathogen started killing many planted and native elm trees in Ohio. It was not until 1957 that the disease made its way to Kansas. Today DED has been reported throughout the state and has destroyed virtually all the large old growth native elms.
There are many reasons oaks decline. This has occurred throughout the range of oak in both forest and urban situations (*picture of range). It is not limited to any one species or species group. Incidences have been most frequent and severe among red, pin, and black oak in the red oak group and among white, bur, and chestnut oak in the white oak group. This is most notable in the central and eastern regions of the state. Oaks face many challenges in this state and this is a complex issue that has many factors such as biological and environmental, that creates unfavorable situations for oaks.