Liquidambar Styraciflua - Infection On Liquidambar Styraciflua

Infection On Liquidambar Styraciflua

The imperfect fungus Tubakia dryina Sutton is a leaf parasite reported to occur on a wide range of host plants, including species of Sweet Gum (Liquidambar styraciflua L.). Limber and Cash reported that leaf spots produced by this pathogen on several different genera of forest trees were 2-5mm diam(eter) with regular margins. During the summer of 1994 in the Nacogdoches County area of Texas, a prominent leaf spot on Sweet Gum was widespread. Infected leaves had numerous necrotic lesions, each surrounded by a reddish halo. The lesions tended to merge resulting in large areas of dead tissue. Infection and fungal development of Tubakia dryina were investigated on leaves of sweet gum using a combination of microscopic techniques. T. dryina infection on Sweet Gum has been associated with the disease red leaf spot. Results of this investigation indicate that T. dryina can penetrate leaf tissue directly, thus having the ability to initiate infection on both upper and lower leaf surfaces. In other regions of the U.S., Sweet Gum populations may not be as susceptible to local populations of this fungus. Environmental stress factors may also be involved, as reports have indicated that herbicide application and chlorosis caused by iron deficiency may increase susceptibility of T. dryina. Tannins (a type of biomolecule found in trees to protect it from fire, insects, and bacteria) have been reported to occur in healthy tissue of a variety of plants including sweet gum. They may prevent pathogen invasion by inhibiting fungal enzyme activity. Although cells of healthy sweet gum tissue appear rich in tannins, these materials apparently were not effective in preventing fungal colonization by T. dryina.