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Verticillium Wilt, often called Maple wilt, is a very common disease that attacks a large number of trees. It is caused by a soil-inhabiting fungus called Verticillium. The disease fungus can be spread by many methods including from plant-to-plant, through the soil, groundwater and often by infected pruning equipment that has not been properly sanitized. The disease normally enters the tree through the soil, but can also be introduced into a tree through a wound. Once in the tree, the fungus begins to spread throughout the tree’s vascular system. As the fungus level increases, the tree’s vascular system becomes blocked preventing the tree from adequately moving water and nutrients throughout the tree.
The first signs that a tree has a Verticillium Wilt infection is the yellowing and then browning of leaves at the ends of some branches. Initially the yellowing and browning of the leaves is spotty throughout the tree and does not follow a uniform pattern. As the fungus begins to block the vascular system, the browning of leaves becomes more acute and more wide-spread. New leaves generally are either non-existent, undersized or yellowed.
As the disease spreads, the infected tree may slowly die branch by branch over several seasons. The symptoms and severity of Verticillium wilt are much more harsh during droughts when the tree’s vascular system is already stressed.
There is no chemical control for Verticillium Wilt, but there are several steps that can be taken to help control the spread of the disease, as well as to enhance a tree’s ability to control or even contain the disease. These include pruning, fertilizing and watering.
Prune and remove all dead wood. The pruning should be a few inches below the diseased area, so as to remove as many of the fungal concentrations as possible. When pruning do not remove branches that have recently wilted as they may reflush again in a few weeks or the following spring. When pruning be sure to properly sanitize the pruning tools after each cut.
Give the tree a very good fertilization with a slow release nitrogen blend. Apply the TreeHelp Annual Care Kit, as this treatment contains an appropriate fertilizer, as well as a mycorrhizal treatment and biostimulant to assist the tree in taking up and metabolizing moisture and nutrients.
It is important to give a tree suffering from verticillium wilt a deep root watering at least twice or three times a week. The objective of a deep root watering is to ensure that the water penetrates deep into the soil, to a depth of at least 24 to 36 inches so that the entire root zone is hydrated. The easiest way to give a large tree a deep root watering is to place either a sprinkler or a soaker hose over the tree's drip line and let it run for about 2 hours, ensuring lots of water penetrates the soil. A deep root watering is much better than frequent shallow waterings, which do not get moisture to the lower roots. During periods of extreme drought you may also want to consider spraying the soil around the tree's root zone with Hydretain Root Zone Moisture Manager. Hydretain is a unique and advanced product specifically designed to assist a tree in dealing with drought stress. It works like a natural magnet to hold water near the tree's root zone and keep the root zone hydrated during periods of drought stress.