- Wilting symptoms of shade trees can occur for a variety of reasons including winter injury, canker diseases, transplanting and establishment, drought, and salt damage.
- Is a common disease problem occurring on maples caused by the common soil fungus Verticillium spp. Other commonly grown trees that are susceptible to Verticillium Wilt include ash, black locust, catalpa, cherries, and other stone fruits, elm, golden rain tree, horse chestnut, magnolia, redbud, serviceberry, smoke tree, tulip tree, and tupelo.
- Early symptoms usually start as a yellowing or off-color of scattered branches in the canopy. These symptoms are usually followed by wilting and sudden dieback of infected limbs especially during drought or in the heat of summer.
- Eventually, the entire plant may wilt and die, however, established trees may live for years with dieback symptoms before succumbing.
- Sunken cankers with bark splitting may develop on infected limbs.
- A partial list of resistant trees includes all gymnosperms (pine, spruce, fir, etc.), crabapple, beech, birch, dogwood, sweetgum, hawthorn, hornbeam, hickory, katsura tree, linden, honey locust, oak, sycamore, walnut, and willow.
- Is the most common cause of death of the mimosa or silk tree (Albizia sp.) in Maryland.
- It is caused by the soil fungus, Fusarium spp.
- Early symptoms usually start as described above. Wilted and dead leaves may remain hanging on diseased twigs and branches. Pink spores may also be visible on the bark of infected trees.
- A partial list of resistant trees includes A. polyphylla, and the cultivars such as Charlotte, Tyron, and Union.
Dutch elm disease
- Is the most destructive wilt disease of elms in Maryland. This disease is spread by several species of bark beetles (elm bark beetle galleries).
- Early symptoms usually start as described above. Wilted and dead leaves may remain hanging on diseased twigs and branches.
- A partial list of resistant elms includes all Chinese, and Siberian elms, and cultivars such as Dynasty, Liberty, Frontier, Homestead, New Horizon, Pathfinder, Regal, Patriot, Sapporo Autumn Gold, and Urban.
Since these wilt fungi can live for many years in the soil replanting susceptible plants in the same soil is not an option. Prompt pruning of symptomatic limbs well below the last visible leaf symptoms can slow down disease spread. The most effective controls for homeowners are to use resistant tree species and adopt cultural practices that promote plant vigor such as watering during drought, pruning out all wilted or dead branches, proper fertilization, and the use of mulches to conserve soil moisture.
Laboratory culture of these fungi is the only positive way to identify Verticillium wilt, Dutch Elm disease, or Mimosa wilt from other fungal problems. However, a diagnostic feature of these diseases is a dark greenish-brown streaking of the sapwood under the bark of infected branches or twigs. This symptom can best be seen by cutting into the bark at the base of freshly wilting branches in the summer.
Systemic chemical options are expensive and should probably be reserved for old specimen plants. Chemical controls are not available to homeowners and have to be applied by a licensed tree care professional. Once the plant is infected, disease control is limited and probably will not give satisfactory results on severely diseased trees.