Spring dead spot

What is spring dead spot?

Spring dead spot is caused by soil fungi in the genus Ophiosphaerella. Missouri Extension lists O. herpotricha, O. korrae and O. narmari. UC IPM notes O. korrae was formerly called Leptosphaeria korrae. The same O. korrae causes necrotic ring spot on Kentucky bluegrass, but on bermudagrass it causes this disease.

The fungi attack roots, stolons and crowns in late summer, fall and winter. NC State says they do not kill the grass outright but make it more likely to suffer freezing injury. That is why the disease is worst near the northern edge of bermudagrass country and after very cold winters. The damage only shows when the lawn tries to green up in spring.

Intensely managed bermudagrass, like sports fields, golf courses and heavily fed lawns, is hit hardest. Missouri Extension says it usually appears three to four years after a lawn is planted. In summer, bermuda slowly creeps back into the dead patches, but weeds often move in too.

Symptoms and signs

• Round or arc-shaped patches of bleached, straw-colored grass that stay dead when the rest of the lawn greens up in spring
• Patches from about 6 inches to several feet across, often slightly sunken
• Roots, stolons and rhizomes dark brown to black and rotted
• Patches come back in the same spots each spring and get bigger
• Weeds or bermuda fill the centers in summer, giving a ring look

Spring dead spot identification: what to look for

• Symptoms: Round, slightly sunken, bleached straw-colored patches at spring green-up. UC IPM gives 6 to 12 inches; NC State and Missouri Extension say up to several feet. Patches can merge into arcs.
• Symptoms: Roots, stolons and rhizomes are dark brown to black, rotted and brittle, most visible at the patch edge.
• Signs: UC IPM notes dark, oval resting bodies (sclerotia) can sometimes be seen on stolons.
• Timing: Infection in late summer and fall. UC IPM says new infections start when air temperatures are about 70 to 75°F and continue as bermuda goes dormant. Symptoms show in early spring.

Disease cycle

The fungi survive in old thatch, roots and stolons as fungal threads and small resting bodies. In late summer and fall, they colonize roots, stolons and crowns, and keep working as the bermudagrass goes dormant. The weakened plants are more easily killed by winter cold. In spring, the dead patches show up at green-up. Bermuda slowly grows back in over summer, and the cycle repeats in the same spots the next fall. It spreads on infested sod and infected plant parts.

When to look: Look in early spring as bermudagrass greens up. Prevention steps happen in late summer and fall, when the fungus is infecting roots.

Spring dead spot look-alikes

A few things get mixed up with it:

• Winterkill: Missouri Extension says spring dead spot is often confused with winterkill. Spring dead spot comes back as round patches in the same spots each year, with black, rotted roots and stolons.
• Large patch (Rhizoctonia solani): Large patch also shows at spring green-up, but mostly on zoysia, with orange patch edges and rotted leaf sheaths rather than black roots.
• Take-all root rot (Gaeumannomyces graminis): Another root rot of warm-season grass. It makes irregular yellow patches rather than sharp round dead circles at green-up.

How to manage spring dead spot

Cultural control

• Do not fertilize bermudagrass within about 6 weeks of winter dormancy, as NC State advises.
• Avoid heavy summer nitrogen. Missouri Extension says too much nitrogen in summer makes symptoms worse the next spring.
• UC IPM and Texas A&M suggest ammonium-based nitrogen, but NC State research found the best nitrogen form depends on which fungus is present.
• Keep thatch under 1/2 inch with yearly dethatching and core aeration.
• Improve drainage and avoid overwatering, but water enough in summer to prevent drought stress.
• Raise mowing height in late summer and early fall.
• In spring, spike or aerate dead patches to help bermuda spread back in. NC State warns some pre-emergent weed killers (dinitroanilines) slow that recovery.

Chemical control

Fungicides give mixed results. UC IPM calls the disease difficult to manage with fungicides, and Missouri Extension does not currently recommend them in the Midwest. Where they are used, they go on preventively in late summer or early fall, with enough water to reach the roots; NC State ties timing to soil temperatures of 60 to 80°F. UC IPM lists azoxystrobin and DMI fungicides. Mapping patches in spring lets fall treatments target only problem areas. Use only products labeled for this use; the label is the law.

Use only products labeled for this disease and this site; the label is the law. For trees, work with an ISA Certified Arborist. If you hire someone to apply pesticides, make sure they hold your state’s pesticide applicator license; the rules for each state are in our pesticide applicator license guide.

Prevention

• Plant clean sod from fields without the disease.
• Choose bermudagrass cultivars Missouri Extension lists as more resistant, such as 'Midlawn', 'Patriot' or 'Yukon'.
• Avoid cultivars Missouri Extension lists as susceptible, such as 'Tifway' and Arizona common.
• Keep turf vigorous but not overly lush going into fall.

When to call a pro

If dead patches return every spring on a bermudagrass lawn or sports field, have roots checked by a plant disease lab, then talk to a licensed pesticide applicator about fall timing. See our pesticide applicator license guide. Fixing poor drainage helps too.

Related guides: Weed identification guide · All pests and diseases

Questions about spring dead spot

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