Have you noticed that your trees are looking a little sad lately? Do they have drooping branches or curled and browning leaves? If so, this could be caused by something as simple as over or under-watering. It could, however, also be caused by a tree condition known as verticillium wilt. Read on to learn about this common condition that affects many trees and is highly prevalent in the Phoenix area. Suppose you discover that your trees might be infected. In that case, it is paramount that you call an arborist to inspect your trees immediately.
A soil-borne fungus, "Verticillium dahliae," causes Verticillium wilt. Verticillium is a prominent disease affecting over 300 plant species, including trees, vegetables, berries, and flowers. Unfortunately, once a plant gets infected, it becomes tough to remove; that's why preventative measures are necessary. The only way to ensure your plants will not get verticillium wilt is to have a trained arborist inspect your yard at least twice a year. This way, a problem can be caught and managed before it gets out of control.
Fungus is the leading cause of verticillium wilt. The fungus lives in the xylem (veins that carry water through the tree.) These tubes block water flow, causing the plant to wilt and die back. Unfortunately, the fungus also poisons the plant with toxins. The disease can occur acutely or develop into a complete chronic condition, which means it will continue to grow and return year after year. In acute(one-time) infections, a tree branch or section will wilt and brown very quickly. Other branches will soon follow until all of the branches are affected. Leaves may also be yellow between the veins and will drop prematurely. Branches may die back. Acute infections occur when the fungus lives in the newest wood.
If your tree suffers from a chronic condition, the leaves will be smaller than usual and brown on the edges. As a result, the tree may grow poorly and produce abnormal, inconsistent seeds. However, the tree will not wilt or die quickly but will decline slowly over time. Chronic infections occur when the fungus lives in the older parts of the tree.
The fungus that causes verticillium wilt lives in the soil. It gets into the plants through its roots, often entering through wounds that are normal with growth. Such as wounds that occur as the roots push through hard soil. The Verticillium fungus is abundant in many types of soils. It has yet to be determined how it can lay dormant for years before suddenly attacking a tree. However, it is possible that stress on the tree, such as a drought or poor soil, can make it more likely to suffer from an infection. Arborists know this as the "disease triangle," which explains that three factors need to be present for a tree to get sick. The disease or fungus must be present, the tree must be susceptible to the condition, and the environment must be suitable for the disease to develop.
No treatments can remove the fungus from the soil where it survives. Therefore, keeping the trees in full health and having them routinely inspected is the best way to prevent this terrible condition. Trees are great at compartmentalizing diseases; if the tree is healthy, it will have a much higher chance of warding off the problem. You will not need to remove trees that have been infected, as the fungus lives in the soil it will not spread through the air. However, you will have to remove infected or dead branches to keep chronically ill trees looking as healthy as possible. At the same time, you treat the real cause of the condition in the soil.
Because the fungus lives in the soil, if you have a tree that dies from verticillium wilt, you should replace the tree with a different type of tree resistant to the condition. Luckily, many plants are unaffected by Verticillium wilt. These include conifers, crabapple, beech, hawthorn, hickory, white oak, and poplar. So when a tree dies from Verticillium wilt, replacing it with one of these resistant species can help to ensure a steady source of summer shade.
How did this happen to my tree?
The fungus that causes verticillium wilt can survive in the soil for up to 10 years, even through the coldest winters. If you plant a potential host near the fungus, the roots of that plant stimulate it to germinate and produce spores. Then, they infect the plant, entering through its roots. The fungus moves upwards through the plant and plugs the plant's vascular system responsible for transporting water. The plugging of the vascular system causes the tell-tale wilt and eventually kills the tree.
How to help my tree:
There is no fungicide treatment to eliminate verticillium wilt. However, actions can be taken to help the tree live longer and maintain its aesthetic value. Managing verticillium wilt includes proper pruning, watering, and fertilizing. Suppose very little of the crown is affected. In this case, you can remove the infected areas from their primary connection where there is no sign of the disease. If too much of the tree needs to be removed, it may be more beneficial to remove the entire tree and start over with one of the more resistant species. Water during dry periods, mainly if they occur in summer or fall. Fertilize if needed with low nitrogen, high potassium fertilizer. Excessive fertilization increases problems with this disease. Promptly remove plants that have been killed by verticillium wilt, and also remove the root system. Throw away infected plant material in a sealed trash can. A professional, such as a tree removal service, should be called if an entire tree needs to be removed.
Hopefully, your trees are looking healthy, or if they are a little sad looking, hopefully, it is just from lack of water. If, after reading this, you think verticillium wilt might be the issue, call an arborist and have them inspect your trees as soon as possible. This could save you time, money, and your trees!