Department of Soil&Crop Sciences

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Brown Patch

Rhizoctonia solani (Main fungus listed)
Rhizoctonia oryzae
Rhizoctonia zea
Rhizoctonia cerealis (yellow patch)

DISEASE SYMPTOMS:

Circular or irregular shaped patches of light brown, thinned grass; turfgrass can be yellowish and may have a smoke-ring on outside edge - especially in the morning hours on cool season grasses; turf in the center of the ring may recover, leaving a ring effect; spreads rapidly; patches up to several yards in diameter; leaf sheaths become rotted and a gentle tug on the leaf blade easily separates from the runner; usually does not discolor roots; fungus attacks the base of the leaf sheath; get a water soaked , dark grass that soon wilts and turns brown.

HOST GRASSES:

Major Hosts: St. Augustinegrass, Zoysiagrass, American buffalograss, Annual bluegrass, Creeping bentgrass, Colonial bentgrass, Tall fescue, Perennial ryegrass.

Others: Bermudagrass, Centipedegrass, Bahiagrass, Fine fescues, Kentucky bluegrass.

DISEASE CYCLE:

Disease develops rapidly when air temperatures are between 75 and 85 degrees and wet conditions are present-Spring, Fall and sometimes mild Winter conditions; generally subsides when air temperatures exceed 90 degrees; foliar attacking fungus; occurs following extended leaf wetness for 10 hours per day for 2 to 5 days; leaves, stems, crowns and roots may be infected.

FACTORS THAT MAY PROMOTE DISEASE DEVELOPMENT:

Cool, wet or moist conditions; leaf blades with dew or free water on them for extended periods; excessive nitrogen and irrigation; lack of air movement; poor soil drainage; excessive thatch; compacted soils-lack of aerification; presence of active fungi; vigorous growth of turfgrass.

CULTURAL CONTROL:

Improve soil drainage; remove dew in early morning by mowing or watering or whipping; cultivate by coring or slicing; avoid excessive nitrogen and irrigation; reduce shading; improve air movement.

CHEMICAL CONTROL:

Most fungicides will do an effective job if used on a preventative basis-hard to destroy the fungus once it is established on the turfgrass. Many fungicides labeled to treat Brown Patch-only those which seem to be most effective are listed below.

Specific Fungicide Recommendations
Fungicide
(chemical name)
Efficacy Application Interval Example of Products
(trade names)
Azoxystrobin Good to excellent 14 to 28 days Heritage
Triadimefon Fair to good 30 days Bayleton
Myclobutinil Good to excellent 14 days Eagle, Immunox
PCNB Good to excellent 21 to 28 days Terraclor, Turfcide
Mancozeb Fair to good 7 days Fore, Dithane, Protect, Penncozeb
Fenarimol Fiar 7 to 14 days Rubigan, Patchwork

REFERENCES:

  • Duble, R. L. 2001. Turfgrasses-Their Management and Use in the Southern Zone. Second Edition. Texas A&M University. College Station, Texas.
  • Emmons, R. D. 2000. Turfgrass Science and Management. Third Edition. Delmar Thomson Learning. Albany, New York.
  • Turgeon, A. J. 2002. Turfgrass Management. Sixth Edition. Prentice Hall. Upper Saddle River, New Jersey.
  • Beard, J. B. 2002. Turfgrass Management for Golf Courses. Second Edition. Ann Harbor Press. Chelsea, Michigan.
  • Taylor, G. R. - Editor. 2000. Turfgrass Pesticide Recommendations 1999-2000. Extension Publication SCS-1991-01. Texas A&M University. College Station, Texas.

Texas Plant Disease Handbook

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