Platanus spp.
Wilt (fungus – Cephalosporium diospyri): This fungus has been found repeatedly in large sycamores. The fungus, when introduced into seedlings, produces symptoms including sudden wilting and browning of leaves, sudden blighting of twigs forming “shepherd’s crooks”, yellow discoloration, and defoliation. How widespread this fungus is in Texas sycamores is not known.
Botryodiplodia Canker (fungus – Botryodiplodia theobromae): This fungus is known generally as a weak or facultative parasite with a wide host range. However, in Texas it has caused a rapid death of sycamores. The fungus produces cankers on branches and the main stem. It is favored by high temperatures and drought stress conditions. Trees weakened by the Cephalosporium wilt fungus are more vulnerable to attack. Broken terminals in twigs are the best places for the fungus to enter. It has been a common problem in sycamores. Prune out dead and dying branches below the cankers. Sterilize pruning tools with 10 percent bleach solution between cuts. Spraying for anthracnose with benomyl will also help to control Botryodiplodia.
Sycamore Anthracnose (fungus – Gnomonia plantani): Sometimes called blight and scorch. A single attack seldom causes harm but if the tree is infected several years in succession it will weaken a tree, making it susceptible to borer attack and winter injury. The first symptoms, sudden browning of single leaves or clusters, may be confused with late frost injury. Later dead areas appear along or between the veins, usually starting at the leaf edge. Leaves fall prematurely when heavily infected and trees often remain bare until late summer, when new leaves form. Infection of small twigs causes sunken areas, called cankers, and slightly raised margins. When the canker completely girdles the twig, killing it, this is called the shoot blight stage. The fungus can overwinter in fallen infected leaves and in twig cankers. In southern Texas it can pass the winter in the spore stage on dormant buds. Severity of attack depends on weather conditions during the two week period following leaf emergence. Frequent rains and cool temperatures favor rapid spread. Below 55oF. injury will be severe and above 60oF, little or no injury. Control: Prune out dead twigs in fall. Burn all dead twigs and fallen leaves. Spray with recommended fungicide when leaves unfurl, when leaves are half-grown, and when leaves are fully grown. Trees repeatedly attacked should be well fertilized in spring to increase their vigor.
Leaf Spot (fungi – Mycosphaerella platanifolia, Phyllosticta plantani, and Septoria platanifolia): Several fungi cause disease of minor importance that can be controlled by the spray schedule suggested for control of anthracnose. Phloeospora multimaculans:known mainly in Texas. Irregular, dark brown to purple spots one-eighth to one-fourth inch in diameter on the upper leaf surface. Often with a brown center. Spots are brown with darker border on lower surface. Spots may coalesce to produce a dirty-brown colored leaf. Defoliation may occur.
Powdery Mildew (fungi – Microsphaera alni and Phyllactinia guttata): Makes appearance mainly in late summer. May be present on older growth but usually most severe on new growth, which may be distorted, stunted, and covered with a white growth and white spores.
Canker-Stain Disease (fungi – Ceratocystis fimbriata f. sp. plantani): It can be lethal to sycamore, but is much more important as a killing disease of London plane (Platanus acerifolia): Since it is spread almost entirely by man, through pruning, it is essentially a shade tree disease. Leaves are dwarfed and sparse in part or all of the tree top. The staining cankers occur on trunks or branches. The first symptom on the yellow or green bark is a brown to black lens-shaped discoloration. Cankers may become 20 to 40 inches long in one year, but usually only two inches wide. Cankers widen each year, and often coalesce, girdling the tree or branch. Older cankers shed their darkened, dead bark exposing the wood, which dries, cracks, and turns black. The reddish-brown or bluish-black discoloration of the wood, in cross section behind the cankers, is the most distinctive symptom. Stain patterns are radial, generally reaching the pith. The fungus sporulates abundantly on newly-killed wood in wet weather from May until October. It produces two kinds of asexual spores; one, long and clear; the other, short and brownish. It also produces a long-necked, pear-shaped, sexual fruiting structure. Avoid injuring the tree. Prune out dead limbs during winter. Be sure to dip the pruning tool in 10 percent bleach solution before each cut to avoid spreading the fungus. Treat cankers with protective paint.
Sooty Blotch (fungus – Gloeodes pomigena): Sometimes forms on shoots of sycamore. The dark surface mycelium can usually be rubbed off with the fingers.
Mistletoe (parasitic plant – Phoradendron serotinum): A seed-producing higher plant that parasitizes sycamore in the south.
Shoestring Root Rot (fungus – Armillaria mellea): Two forms of the fungus can usually be found under the bark at ground level. These are black “shoestring like” rhizomorphs and a white fan-shaped fungus growth. (See section on Mushroom Root Rot)
Cotton Root Rot (fungus – Phymatotrichum omnivorum): (See section on Cotton Root Rot)
Trunk Rots (fungi – Hydnum erinaceus, Fomes sp., Ganoderma sp.): Heart rot fungi can hollow out the entire central cylinder of a tree. The tree declines in general and the presence of the fungus is known when it fruits on the side of the tree. The annual fruiting structure is a white, rounded, spongy mass with long, slender white teeth on the bottom. There is no control – only prevention, by avoiding wounding the tree. (Fomes applanatus): This fungus enters wounds and causes a white, mottled trunk rot. The tree declines in general and the presence of the fungus is known when it produces a fruiting structure from a wound. This hard, woody, shelf-like perennial structure may attain a width of two or more feet. The upper surface is smooth, zoned, and grayish or grayish black, whereas the undersurface is white when fresh, but becomes yellowish with age. The undersurface turns brown when bruised and is a favorite medium for artists. There is no control – only prevention, by avoiding wounding of the tree.
