Managing Armyworms in Your Grass Quickly

Credit: Lane Tredway: Pyriculria grisea: fescues, kikuyugrass, ryegrasses, St. Augustinegrass: irregular blighted patches of grass with bleached areas with dark margins on leaves; ryegrass establishes a fishhook look: daytime temperature levels of 8595F; high humidity or rains; overwatered and overfertilized turf: irrigate appropriately; do not overfertilize; decrease shading; boost air movement: fungicides are available, but cultural controls are more useful Fusarium spot damage to bentgrass turf.

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McCain: Microdochium nivale: yearly bluegrass, bluegrasses, fescues, ryegrasses, zoysiagrass: circular spots of 12 inches that can expand to 12 inches; leaves first appear watersoaked, then reddish brown, and lastly bleached; minute, gelatinous spore masses often seen on dead leaves; white or pinkish fungal threads might be seen in early morning; more widespread in Central and Northern California: consistently cool temperatures (4065F) and wet conditions; high nitrogen applications in fall; neutral or alkaline soil pH; pathogen survives in lawn residues: reduce shade and improve soil aeration and water drain; water suitable length of time; avoid excess nitrogen, especially in fall; keep soil pH in between 6.56.7.

Credit: M. Ali Harivandi: Bipolaris spp. and Helminthosporium spp.: bermudagrass, bluegrasses, fescues, kikuyugrass, ryegrasses, zoysiagrasses: circular to extended brownish spots with brown centers and dark brown or purple verge on leaf blades, sheaths, and stems; crowns and roots often have a dark brown rot; crown-infected plants might pass away in hot, windy weather condition, leaving thinned areas throughout the grass; spores are windborne: warm temperatures (7090F) for bluegrasses, ryegrasses, and fescues; cool temperature levels (6070F) for bermudagrass and zoysiagrass; high humidity; low clipped turfgrass; most serious with excess nitrogen fertilization or deficiency: minimize shade; improve soil aeration and water drain; prevent dry areas and excessive nitrogen fertilizer; keep as high a cutting height as possible: fungicides readily available however often 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 turfs: little, circular areas (26 inches) that run together; blackened leaf blades quickly wither, turn reddish brown, lie flat, stick, and appear greasy; roots may be brown; in humid conditions, masses of fungal mycelium may appear: low spots that stay damp; warm temperature levels (8095F daytime, > 68F night time); endures as spores in soil for long periods: minimize shading; enhance soil aeration and water drainage; water appropriate length of time; avoid cutting wet grass and applying high levels of nitrogen throughout hot, humid weather: fungicides readily available but mainly prevented by cultural practices in California Patches of high fescue turfgrass contaminated with Rhizoctonia blight.

Garden Insect Recognition Guide for 2026

Credit: Arthur H. McCain: Rhizoctonia solani AG 2-2LP: bermudagrasses, kikuyugrass, St. Augustine yard, zoysiagrass: first appears as small, irregular brown patches or rings that can increase the size of to many feet in size; centers may recuperate resulting in rings of infected lawn; leaves and sheaths become watersoaked, wilt, turn light brown, and pass away; plants take out easily from soil with rotten stolons, in light infestations, roots typically not infected and plants frequently recuperate; 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: reduce shading and enhance soil aeration and water drainage; water proper length of time to a depth of 46 inches; prevent excess nitrogen in the fall; keep thatch less than 1/2 inch: fungicide useful 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 might kill turfgrass in patches that are 28 inches in size, or the disease might happen over large locations without eliminating the plants; pink web of fungal threads bind the leaves together; search for pink, gelatinous fungal crusts forecasting from the leaves to help identify this disease: typical under conditions of moderate air temperatures (6075F) and extended durations of leaf wetness; frequently appears on plants lacking in nitrogen throughout periods of cool or warm temperature levels if there is adequate wetness (e.g., excess irrigation or rains): proper irrigation and fertilization can decrease the incidence; appropriate nitrogen typically can avoid this illness from occurring; prevent drought tension by irrigating turfgrass based on evapotranspiration requirements of the turfgrass; provide sufficient air blood circulation; decrease shading: fungicides rarely required other than in serious cases Rust damage to bluegrass foliage.