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theses

Anthracnose, caused by the fungus Colletotrichum cereale Manns sensu lato Crouch, Clarke, and Hillman, is a devastating disease of annual bluegrass [Poa annua L. forma reptans (Hausskn.) T. Koyama] (ABG) putting green turf. Four field trials were conducted from 2009 to 2011 to examine the effects of sand topdressing and midseason cultivation on anthracnose severity of ABG turf mowed at 3.2-mm. Increased rate of spring (0, 1.2 and 2.4 L m-2) and summer (0, 0.075, 0.15, 0.3 and 0.6 L m-2) topdressing reduced disease severity linearly throughout most of 2009 and 2010. However, increased summer topdressing rate produced a quadratic decrease in disease severity by mid-2010; increased spring topdressing rate reduced the amount (rate) of summer topdressing needed to reduce disease. Sand topdressing during the onset of disease (approximately 10% of the plot area infested with C. cereale) in 2009 and 2010 caused a 9 to 14% increase in disease severity 16- to 18-d after treatments were initiated. However, these disease increases lasted only 6- to 9-d and continued sand topdressing reduced disease severity 13 to 20% by the end of each growing season. Verticutting, scarifying and solid-tining increased disease severity up to 18, 10 and 5%, respectively, when performed when symptoms were present (11 to 20% disease severity). These cultivation treatments reduced disease severity relative to the control before treatments were initiated again in 2010 (second trial-year); however, verticutting, scarifying and solid-tining increased disease once again by late-2010. Weekly grooming reduced disease severity up to 9% relative to the control during both trial-years. Cultivation typically did not affect disease severity when curative fungicide was also being applied. Deep vertical cutting (7.6-mm) increased disease 4% relative to the control and 5% relative to shallow vertical cutting (1.3-mm) on 6% of rating dates. Shallow vertical cutting produced small, marginally significant reductions in disease severity compared to the control on 16% of rating dates. Spring topdressing is a strategy for anthracnose suppression that may also reduce the rate of summer topdressing needed to reduce disease severity. Additionally, cultivation practices that only affect leaves, such as grooming, may slightly reduce anthracnose severity.

ETD_5145

M.S.

Includes bibliographical references

Includes vita

by James Warren Hempfling

doi:10.7282/T3PR7T1X

ETD graduate

The author owns the copyright to this work.