Kentucky Bluegrass Disease Management
SUMMER PATCH is the #1 disease threat to KBG. Caused by Magnaporthe poae, it attacks roots when soil temps exceed 65°F and symptoms appear as circular dead patches in mid-summer heat. Prevention: apply a DMI fungicide (propiconazole) as a soil drench in late May when soil temps hit 65°F — this is PREVENTIVE, not curative. Once symptoms show, the roots are already dead. Brown patch (Rhizoctonia) appears in hot humid weather with excessive nitrogen — reduce N inputs and improve air circulation. Dollar spot shows tan spots the size of a silver dollar — indicates low nitrogen, so a light fertilizer application can help. Leaf spot (Drechslera/Bipolaris) hits in cool wet springs — raise mowing height and avoid evening irrigation. KBG is more disease-prone than tall fescue overall. Choose disease-resistant cultivars when seeding.
Frequently Asked Questions
What is summer patch?
Summer patch (Magnaporthe poae) attacks KBG roots in hot soil, killing grass in circular to crescent-shaped patches. Symptoms appear in mid-summer but infection starts in late spring when soil hits 65°F.
How do I prevent summer patch?
Apply preventive fungicide (azoxystrobin or propiconazole) when soil temps reach 65°F in late spring. Reduce nitrogen, raise mowing height, and water deeply but infrequently in summer.
Does KBG get brown patch too?
Yes, especially in warm humid weather. KBG is susceptible to both brown patch and dollar spot. This higher disease pressure compared to fescue is the tradeoff for KBG's self-repairing ability.
Will KBG recover from disease damage?
Often yes, thanks to rhizomes. KBG can regrow into diseased areas from the edges via underground runners. This self-repair ability is its biggest advantage over fescue for disease recovery.
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