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Title: REACTIVATION OF BENTGRASS DEAD SPOT AND GROWTH, PSEUDOTHECIA PRODUCTION AND ASCOSPORE GERMINATION OF OPHIOSPHAERELLA AGROSTIS

Author
item KAMINSKI, J - UNIV OF MD COLLEGE PK MD
item DERNOEDEN, P - UNIV OF MD COLLEGE PK MD
item MOMEN, B - UNIV OF MD COLLEGE PK MD
item ONEILL, NICHOLE

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/30/2002
Publication Date: N/A
Citation: N/A

Interpretive Summary: The causal agent of a newly described disease of bentgrass is the fungus Ophiosphaerella agrostis. Little is known about the biology of the fungus or the development of the disease it causes, bentgrass dead spot. The disease has now been found in 12 states, causing unsightly dead patches in three species of grass. The patches do not recover and turf managers are currently testing various fungicides to attempt to control the disease. In the present research, we determined some basic biological properties of the fungal pathogen, including growth rate, growth temperature optima, and light and temperature requirements for spore production. In studies of reactivation of the disease after winter dormancy, we found that the fungus resumed disease-causing activity over a wide range of temperatures but grew best at warmer temperatures. The information reported in this study will enable scientists and turf specialists to better understand and predict the onset and development of bentgrass dead spot.

Technical Abstract: Ophiospaerella agrostis incites bentgrass dead spot (BDS) of creeping bentgrass. Little is known about the biology of O. agrostis. The primary goal of this study was to determine some basic biological properties of the pathogen and epidemiological components of the disease. Previously infected, winter-dormant creeping bentgrass field samples were incubated at temperatures ranging from 15 to 30 C. Between 12 and 28 days of incubation, BDS reactivation occurred at temperatures >20 C, but the greatest increase in BDS patch diameter occurred at 25 and 30 C. The optimum growth rate for O. agrostis isolates was 25 to 30 C, and the slowest growth rate occurred at 35 C. Pseudothecia were produced in vitro on a tall fescue seed and wheat bran mix infested with O. agrostis. Pseudothecia developed under constant light on a benchtop growth hood (13 to 28 C) or in an incubator (25 C), but no pseudothecia developed in darkness. Pseudothecia began to appear in 4 days, with maximum production occurring between 28 and 31 days. Ascospores incubated at 25 C began germinating in 2 h. Germ tubes generally emerged from the terminal ends rather than interior cells of the ascospores. Germination during the first 4 h of incubation was enhanced by both light and the presence of bentgrass leaves or roots. After 18 h of incubation, however, there were few differences in ascospore germination percentages among light and dark treatments or the presence or absence of plant tissue.