Acremonium Wilt, Acremonium (=Cephalosporium) diospyri (Crandall) W. Gams

Leininger, T.D; Solomon, J.D.; Wilson, A. Dan; Schiff, N.M. 1999. A Guide to Major Insects, Diseases, Air Pollution Injury, and Chemical Injury of Sycamore. Gen. Tech. Rep. SRS-28. Asheville, NC: USDA Forest Service, Southern Research Station. 44 p.

Fungus.-Initial infections by conidia likely occur through bark wounds made by insects, animals, or storms.

Injury-Brown leaves appear on one to several branches in spring. The disease develops progressively causing twig dieback, defoliation, and pale-yellow, stunted foliar regrowth (fig. 26). Acremonium wilt is favored by hot weather (> 30º C). Wilted sycamores are susceptible to infection by B. rhodina.

Figure 26. - Sycamore tree with Acremonium wilt.

Control.-Acremonium wilt is mainly a problem in urban areas of east Texas. It has been controlled experimentally by spraying leaves and trunks with fungicides.

Sycamore Decline and Dieback, various causal agents

Importance.-Sycamore decline, sometimes called dieback, has been reported since the 1950’s across the Southen United States. The recurrence of this problem has led some companies to curtail or halt commercial plantations.

Identifying the Disease.-Sycamore decline typically appears as foliar necrosis and branch dieback in tree crowns throughout a plantation (fig. 27a). Individual crown symptoms include sparse foliage, dead branches, and scorched leaves (fig. 27b, c). Similar symptoms can be caused by canker fungi such as C. fimbriata f. platani, B. rhodina, and P scabra, or the bacterium X. fastidiosa, which often is associated with sycamore decline.

Figure 27a Photo by Theodor D. Leininger, USDA Forest Service

Figure 27a. - Sycamore decline, expressed as leaf scorching, thin crowns, and branch dieback, in a 5-year-old plantation in southern Alabama in August. Xylella fastidiosa and Botryosphaeria cankers were present in this stand.

Identifying the Causal Agents.-The combination of environmental and biological agents contributing to sycamore decline may vary. Soil type, seed source, weather (temperature and precipitation extremes), time of planting, and plant culture can affect or trigger decline events. Specific pathogens and insects that attack declining trees are described elsewhere in this guide.

Biology.-Sycamore decline results from a combination of environmental and biological stresses and subsequent attacks by opportunistic pests. An abiotic factor, e.g., soil type or drought, will predispose a tree or stand of trees; and another abiotic or biotic factor, e.g., freezing temperatures or insect defoliation, will trigger a decline that results in mortality from various diseases and insects.

Figure 27b

Figure 27c

Figure 27 - (b.) Tress inside the stand in (a) showing branch dieback and sparsely foliated crowns; (c) dieback and epicormic branching in a 4-year-old plantation. Note the exposed, inactive canker, likely Botryospaeria on the tree at center.

Control.-There is much to learn about sycamore decline. Planting clones with some disease resistance on sites that are well suited for sycamore and avoiding unnecessary wounding may be the best way to prevent sycamore decline.