Fungus on Mimosa Trees
- The wilt diseases of mimosa trees are caused by the fungus Fusarium oxysporum forma specialis perniciosum. The fungus enters the tree through wounds, such as those from pruning or damage to the trunk from lawn mowers or other lawncare equipment. The fungus then spreads through the tissues in the tree responsible for carrying water and sap, which are like the blood of the tree. When the sap and water stop flowing, the tree does not get enough moisture and nutrition to survive.
- The earliest symptoms of fungal infection in mimosas go largely unnoticed. These include brown streaks in the wood directly under the bark, but because you rarely have cause to remove the bark of the tree, you probably won't notice these streaks. As the fungus spreads, the leaves grow smaller than usual, and often yellow or wilt as soon as summer heat kicks in. Later in the season, the trees drop leaves far too early for normal fall leaf drop.
- Fungal wilt infection in mimosa almost always results in the death of the tree. As the fungus progresses, the bark cracks, white liquid seeps from the cracks and the tree smells rotten. Death occurs as early as one month after infection; some trees can survive into the next season, producing stunted and ill leaves before dying. Sometimes the roots survive and sprout again, which sometimes succeeds at sprouting a new tree, but the new growth may suffer from the same disease and quickly die.
- There is no sure-fire cure for the deadly fungal wilt. Surface fungicides cannot get to the inner disease, and systemic fungicides do not work quickly enough to save the tree. Regular watering and application with balanced or low-nitrogen fertilizers help to boost the tree's resistance to the fungus, but this often only extends the tree's life for a little while. Instead, remove infected mimosa trees before they spread the infection to others nearby. Some cultivars, including the Charlotte mimosa, Tyron mimosa and Union mimosa, have a natural resistance to the fungus.
