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Brown Ring Patch - BRS Update


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More Info
									Brown Ring Patch
J.E. Kaminski, Department of Plant Science & F.P. Wong, Department of Plant
Pathology, University of California

                                                                                                          Pat Gradoville, Palos Verdes Golf Club
                                                         Figure 1

     Brown ring patch, also known as Waitea patch,
 is a “new” disease of annual bluegrass putting
 greens that has recently appeared in the western,
 Midwestern and northeastern United States. The
 disease is caused by a species closely related to
 Rhizoctonia oryzae and R. zeae, which are known
 to cause sheath and leaf spot or high-temperature
 brown patch in the United States. The formal name
 of the pathogen (named after its observed sexual
 state) is Waitea circinata var. circinata (Wcc).
                                                         Figure 2
     The disease has been reported in numerous
 locations across the country, including California,
 Connecticut, Illinois, Indiana, Massachusetts,
 Nevada, New York, Ohio, Oregon, Rhode Island
 and Washington.

     Initial symptoms on greens begin as diffuse, thin
 yellow rings or crescents (a few inches to a foot in
 diameter) that can turn golden-brown under hot or
 wet conditions (Fig. 1). Often, the rings will be
 uneven and have a “scalloped” appearance (Fig. 2).
 On low fertility greens, sometimes a green halo can     Figure 3
 be seen surrounding or inside of the yellow rings
 (Fig. 3). Symptoms can be confused with those of                                        Eric Ullrich, Lakeside Golf Club
 yellow patch, fairy ring or necrotic ring spot.

              CAUSAL AGENT
     Abundant mycelia can be seen on the foliage,
 down in the crowns, stolons and in the thatch when
 the soil is moist (Fig. 4). The pathogen tends to
 colonize both the above-ground parts of the plant
 and the thatch, which can result in sunken rings
 where the thatch has broken down. The mycelia can

                                                                                                                                                                             TURFGRASS DISEASE
                                                                                       Brown Ring Patch
be rather fluffy and extensive under wet conditions.                                     suppressed mycelium growth. Like its closely
                                                                                         related relative, R. zeae, Wcc appears to be
    The disease has been observed at daytime                                             naturally resistant to the benzimidazole fungicides.
temperatures ranging from 50ºF to 90ºF, with optimal
temperatures of 70ºF to 85ºF. Because it can actively                                         Superintendents have reported mixed results for
colonize thatch, the disease may be more severe on                                       Wcc control with fungicides; ProStar, Heritage,
putting greens with excessive organic matter                                             Medallion and Endorse fungicides seem to
accumulation.                                                                            consistently provide the greatest level of control.
                                                                                         Since Wcc is often in the thatch layer, adequate
    During the spring and early summer months,                                           application volume (≥ 2 gallons of water per 1000
disease symptoms appear as yellow rings ranging                                          ft2) and/or watering-in materials into the upper
from a few inches up to a foot in diameter. Although                                     thatch layer is important. If the disease is already
infected annual bluegrass generally does not entirely                                    well established in the thatch or turf, multiple
collapse, turfgrass thinning and/or plant death can                                      applications may be needed to completely stop the
occur. Under hot and dry conditions, disease                                             pathogen. In severe cases, recovery from damage
symptoms generally disappear. The disease,                                               is slow due to the amount of crown damage and
however, may recur as temperatures favoring growth                                       thatch degradation. Preventive or early curative
of the pathogen develop in the autumn months. The                                        control is likely most effective.
disease symptoms remained visible until treated with
an effective fungicide.
                                                                                           Figure 4

     Recommendations for control are based on in
vitro testing of fungicides in the lab, a limited field
study in California, and anecdotal evidence and
reports from superintendents.

   In the lab, a number of isolates of the pathogen
were screened on Petri plates against Chipco 26 GT®,
Banner MAXX®, Cleary’s 3336®, Heritage® and
ProStar® fungicides. With the exception of Cleary’s
3336®, all fungicides evaluated in this study effectively

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or approval is intended. All agrochemicals/pesticides listed are registered for suggested uses in accordance with federal and Connecticut state laws and regulations
as of the date of printing. Read and follow all instructions and safety precautions on labels. The user of this information assumes all risks for personal injury or prop-
erty damage. The Connecticut Cooperative Extension System offers its programs to persons regardless of race, color, national origin, sex, age or disability and is an
equal opportunity employer.

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