TURFGRASS DISEASE IDENTIFICATION (P9)
Brown Ring Patch
Causal Agent: Waitea circinata var. circinata/Chrysorhiza circinata (formerly Rhizoctonia circinata)
Susceptible Turfgrass: Annual bluegrass (Poa annua), Roughstalk Bluegrass (Poa trivialis), and creeping Bentgrass
Symptoms: Yellow regular to irregular rings that may become necrotic from a few inches to a foot or more in diameter. Rings are more often brown versus yellow on creeping Bentgrass. Infection can occur within a temperature range of 60 to 85°F with an optimal range of 75 to 80°F. Continuing infection can degrade thatch resulting in sunken rings. Greenish color can be greater inside the affected yellow rings similar to fairy ring. Can be easily confused with yellow patch (cool weather brown patch), but is more tolerant of higher temperatures. Recovery following curative fungicide applications can be slow. The pathogen can colonize the upper root zone and soil in addition to the thatch similar to fairy ring. Can cause thinning or irregular establishment of creeping Bentgrass and Poa trivialis in situations of overseeding of bermudagrass or other warm-season turfgrasses.
Conditions Favoring Disease: Moderate temperatures for extended periods within 60 to 85°F range. Use of some fungicides, such as thiophanatemethyl (TM) have no effect on brown ring patch, so disease may persist with slow recovery following fungicide applications of TM. Infection is more common under dry conditions when compared to the brown patch disease which is more prevalent under wet, water-logged conditions. Also, unlike brown patch, elevated nitrogen fertility does not increase brown ring patch severity, but can help alleviate disease symptoms. As such, brown ring patch is more common in low-nitrogen fertility situations.
- Raise mower height.
- Reduce soil compaction through aerification and use of lightweight equipment.
- Maintain adequate nitrogen and a balanced fertility.
- Avoid drought stress.
- Top-dress and aerate turf, as needed.
- Thatch management—avoid thatch accumulation.
- Avoid use of thiophanate-methyl or other benzimidazoles.
- Apply systemic fungicides on a preventive basis only.
Occurs in: CA, NV, WA, OR, OH, VA, FL, ID, UT, MI, ME, NY, PA, NH, CT, and other states.
Leaf & Sheath Spot/Mini Ring
Causal Agent: Waitea circinata var. zeae/Chrysorhiza zeae (formerly Rhizoctonia zeae) and/or Waitea circinata var. oryzae/Chrysorhiza oryzae
Susceptible Turfgrass: All species of warm- and cool-season turfgrass
Symptoms: The symptoms of leaf and sheath spot can vary dramatically depending on the grass cultivar, climatic and atmospheric conditions, soil, and intensity of the turfgrass management. This disease typically causes thinned areas resembling scalped areas or semi-circular thinned rings in warm-season turfgrass and can be commonly confused with fairy ring or hydrophobic areas. In cool-season turfgrass, small patches of blighted turfgrass that measure 5 inches or more in diameter may exist in conjunction with brown patch. The disease can often have a darker red/orange hue to the infected turfgrass. Leaf spots may, but oftentimes do not, occur. These thin areas can also be slower to respond to fungicides as the disease is most active at high temperatures which can impede turfgrass re-growth.
Conditions Favoring Disease: Symptoms of leaf and sheath spot do not occur as fast as with brown patch or large patch (R. solani), nor do they occur in the same conditions. Infection is most f avored by high canopy temperatures of 83°–97°F. This disease can be quite active in the heat of the summer when temperatures in the turfgrass canopy exceed the 100°F range. Turfgrass that is stressed from drought and over-reliance on irrigation with poor quality water high in carbonates and salinity is more subject to infection. This can be a seemingly hot, dry weather disease as humidity or moisture within the crown is all that is necessary for infection.
- Maintain or apply nitrogen if levels are low.
- Increase the height of cut on greens, especially during drought conditions.
- Increase the air circulation.
- Irrigate turf early in the day.
- Manage or leach salts periodically with heavy irrigation events.
- Reduce thatch.
- Use fans when practical to improve air flow and lower canopy temperatures.
- For best results, use contact or systemic fungicides to prevent brown patch.
- For curative control, use systemic fungicides at water volumes no less than 2 gal/1,000 ft2.
Frequently occurs in: All states.