Lawn Insect Recognition Guide for 2026

Credit: Lane Tredway: Pyriculria grisea: fescues, kikuyugrass, ryegrasses, St. Augustinegrass: irregular blighted patches of grass with bleached spots with dark margins on leaves; ryegrass establishes a fishhook look: daytime temperature levels of 8595F; high humidity or rainfall; overwatered and overfertilized grass: irrigate correctly; don't overfertilize; lower shading; increase air motion: fungicides are offered, however cultural controls are more useful Fusarium spot damage to bentgrass grass.

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McCain: Microdochium nivale: annual bluegrass, bluegrasses, fescues, ryegrasses, zoysiagrass: circular spots of 12 inches that can increase the size of to 12 inches; leaves first appear watersoaked, then reddish brown, and finally bleached; minute, gelatinous spore masses sometimes seen on dead leaves; white or pinkish fungal threads might be seen in early morning; more prevalent in Central and Northern California: consistently cool temperatures (4065F) and damp conditions; high nitrogen applications in fall; neutral or alkaline soil pH; pathogen survives in grass residues: minimize shade and improve soil aeration and water drain; water appropriate length of time; prevent excess nitrogen, particularly in fall; maintain soil pH in between 6.56.7.

Credit: M. Ali Harivandi: Bipolaris spp. and Helminthosporium spp.: bermudagrass, bluegrasses, fescues, kikuyugrass, ryegrasses, zoysiagrasses: circular to elongated brownish spots with brown centers and dark brown or purple verge on leaf blades, sheaths, and stems; crowns and roots frequently have a dark brown rot; crown-infected plants might pass away in hot, windy weather, leaving thinned locations throughout the turf; spores are windborne: warm temperatures (7090F) for bluegrasses, ryegrasses, and fescues; cool temperatures (6070F) for bermudagrass and zoysiagrass; high humidity; low clipped turfgrass; most severe with excess nitrogen fertilization or deficiency: decrease shade; improve soil aeration and water drainage; avoid dry spots and excessive nitrogen fertilizer; maintain as high a cutting height as possible: fungicides readily available but typically not warranted Pythium blight (grease area), caused by Pythium sp., on a ryegrass and bluegrass yard.

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Ali Harivandi: Pythium spp.: all grasses: little, circular areas (26 inches) that run together; blackened leaf blades rapidly wither, turn reddish brown, lie flat, stick together, and appear greasy; roots may be brown; in damp conditions, masses of fungal mycelium might appear: low areas that remain damp; warm temperatures (8095F daytime, > 68F night time); survives as spores in soil for long durations: decrease shading; enhance soil aeration and water drainage; water proper length of time; avoid trimming wet yard and using high levels of nitrogen throughout hot, damp weather condition: fungicides readily available but mostly avoided by cultural practices in California Patches of high fescue turfgrass infected with Rhizoctonia blight.

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Credit: Arthur H. McCain: Rhizoctonia solani AG 2-2LP: bermudagrasses, kikuyugrass, St. Augustine grass, zoysiagrass: first appears as little, irregular brown spots or rings that can enlarge to lots of feet in size; centers may recover resulting in rings of infected grass; leaves and sheaths become watersoaked, wilt, turn light brown, and die; plants take out quickly from soil with rotten stolons, in light problems, roots typically not contaminated and plants typically recover; soil-inhabiting fungi that forms fine, fungal threads in soil or on turfgrass: excess thatch and mat together with cool temperatures (6070F); damp soil conditions: minimize shading and improve soil aeration and water drainage; water appropriate length of time to a depth of 46 inches; prevent excess nitrogen in the fall; preserve thatch less than 1/2 inch: fungicide helpful if illness serious in past Red thread damage to grass foliage.

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McCain: Laetisaria fuciformis: bentgrasses, bermudagrasses bluegrasses, fescues, ryegrasses: red thread may kill turfgrass in spots that are 28 inches in diameter, or the illness may happen over big locations without killing the plants; pink web of fungal threads bind the leaves together; look for pink, gelatinous fungal crusts predicting from the leaves to help determine this disease: typical under conditions of mild air temperature levels (6075F) and extended periods of leaf moisture; frequently appears on plants deficient in nitrogen throughout periods of cool or warm temperature levels if there is adequate moisture (e.g., excess watering or rainfall): appropriate irrigation and fertilization can lower the occurrence; appropriate nitrogen usually can avoid this illness from occurring; avoid drought tension by irrigating turfgrass based upon evapotranspiration requirements of the turfgrass; supply appropriate air blood circulation; reduce shading: fungicides seldom required other than in serious cases Rust damage to bluegrass foliage.