Wet weather creates disease issues for trees in the area

I am getting lots of calls on trees. Leaves are turning brown, curling, and dropping from ash, oak, maple and other trees. Nobody likes to see their tree shed leaves in the summer. Here are a few key points:

This outbreak was caused by the moist weather we had this spring. In general, diseases thrive in wet weather. When tree leaves pop out of their buds in early spring, they are very susceptible to disease. Their tissues are very succulent and their waxy cuticle layer of protection is not yet developed. In most cases, these diseases do not directly affect any permanent part (trunk, roots, and branches) of the tree. Keep in mind that the purpose of leaves is to use their green tissue (chlorophyll) to produce food for the tree. Look at the sick tree. There is still plenty of green tissue producing food for the tree. The tree will be fine. Leaf diseases only cause major harm to a tree when they occur on a regular basis.

Nobody likes to see their trees shed leaves in summer, but this by itself is no cause for worry. A tree can shed 10 percent of its leaves and not be harmed. There is still a lot of green tissue producing plenty of food for the tree.

Sanitation is the key. Rake the leaves as they drop and get the disease out of the area. This will prevent re-infection later this year and next year. Regular pruning can increase air movement within a tree and reduce leaf disease problems.

Don’t confuse these problems with those caused by any borer. Borers destroy the veins of the tree. The first symptom of borer damage is dying back at the top of the tree. This is because the top of the tree is farthest away from the roots and least likely to get the water it needs.

On the other hand, the top of the tree is usually healthy when a tree gets a leaf disease. That is because the top of the tree get lots of sun and wind movement. You will see a crown of healthy foliage on the top of the tree. With leaf diseases, we usually see the worst damage in the shady area of the tree (towards the bottom and the inner portion of the canopy).

(Lance Brower is the community, leadership and economic development extension agent, Stutsman County office, NDSU Extension Service. Contact him at 252-9030 or email lance.brower@ndsu.edu.)

Tags: life, home, trees, garden