• Ash trees (Fraxinus), belonging to the olive family, make useful shade and ornamental trees for your landscape. They have a minor littering problem, as both the leaves and the seeds, shaped like small wings, rain down from the tree and necessitate regular clean up. Your ash trees can also have more serious problems, however, including a number of different tree diseases and a particular moth.
  
  

Anthracnose

• Anthracnose is a very common problem for ash trees; the green ash species is especially affected by this fungal ailment. Anthracnose infects various parts of the tree, including the twigs and buds. This typically occurs in the springtime, aided by rains that spread the disease from one part of the ash to another. Symptoms of anthracnose include necrosis of the leaves and distortion of foliage, with odd-shaped brown blotches breaking out on their surfaces. The ash tree may suffer from defoliation in extreme cases of anthracnose. North Dakota State University advises landowners to rake up ash leaves in autumn so that the fungus responsible for anthracnose is not present in the spring. You may need to apply a fungicide if infections occur repeatedly.
  
  

Ash Rust

• Ash rust is problematic for ash trees in the sense that it takes away from the tree's normal appearance. The disease causes brilliant orange-colored fruiting bodies to grow on the tree, with the leaves and stems showing deformities. Ash rust, brought about by the fungus known as Puccinia sparganioodes, does not harm the tree but it will infect a type of grass, cordgrass, which frequently grows near ashes. The fungi will create spores in autumn that will then result in the disease on the ash trees the next spring.
  
  

Ash Yellows

• Ash yellows creates symptoms such as very slow growth, with the leaves often turning yellowish well before they should. Other indicators of this ash tree problem include dieback of the branches and twigs along with the development of groupings of short branches. Ash yellows can kill an ash tree in a span of two to 10 years. Ash yellows affects species such as white ash and green ash, which both range over most of the eastern half of the United States. The organism that causes ash yellows most likely gains access to the ash tree via insects, according to the North Dakota State University.
  
  

Clearwing Borer

• A type of moth called the clearwing borer can damage ash trees, although the adult moth does not hurt the tree. In its larval stages, this moth will bore into and devour the sapwood of an ash tree and then spend the winter in the tree before advancing to the pupae stage in the spring. The tender tree tissue that serves to conduct nutrients and water to other parts of the tree may suffer damage, harming the overall health of the specimen. The tree may weaken and become susceptible to other pests and diseases. In some instances, severe infestations of the clearwing borer can eventually kill an ash tree, notes the University of Minnesota.