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Brown Patch

Brown Patch. Knowledge Requirements. What are the best diagnostic signs and symptoms of brown patch? Is the pathogen a spore-former or a non-spore-former? How does the pathogen survive adverse conditions? How does the pathogen infect turfgrass plants?

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Brown Patch

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  1. Brown Patch

  2. Knowledge Requirements • What are the best diagnostic signs and symptoms of brown patch? • Is the pathogen a spore-former or a non-spore-former? • How does the pathogen survive adverse conditions? • How does the pathogen infect turfgrass plants? • What species of turfgrasses are susceptible? • How does mowing height affect the signs and symptoms of brown patch? • What effects do nutrients such as N, P & K have on the disease? • What environmental conditions are required for brown patch to develop? • 9. What species of turfgrass are resistant or immune to brown patch? • 10. What turf nutrients suppress brown patch? • 11. In what ways can the environment be manipulated to suppress • brown patch? • 12. Name a contact and penetrant fungicide that will control brown patch. • 13. During what season(s) are preventive applications of brown patch • fungicides applied in GA?

  3. The disease once known as Brown Patch is now considered as 3 distinct diseases. BROWN PATCH Yellow Patch of Cool Season Grasses caused by: Rhizoctonia cerealis Brown Patch of Cool Season Grasses caused by: Rhizoctonia solani (strains AG 1 and AG 2-2IIIB) Rhizoctonia Large Patch of Warm Season Grasses caused by: Rhizoctonia solani (strain AG 2-2 LP)

  4. First we will discuss the disease Brown Patch BROWN PATCH (a.k.a. Rhizoctonia blight) caused by: Rhizoctonia solani (strains AG 1 and AG 2-2 IIIB) Brown Patch affects only cool-season turfgrasses!!!

  5. Rhizoctonia solani (strains AG 1 and AG 2-2 IIIB) • Nonspore-forming fungus. • Survives as sclerotia or dormant mycelium • in thatch, soil or dead tissue. • Initial infection occurs on leaf sheaths and • leaves when night temps are >60°F and leaves • have been wet for more than 10 hrs.

  6. BROWN PATCH Susceptible grasses -All cool season grasses are susceptible.

  7. BROWN PATCH Favorable environment • Night temperatures >60°F (16°C). • More than 10 hrs. of leaf wetness per day for • several days. • - Disease severe at soil pH<6 and on turf subjected • to drought stress.

  8. Morning shade from tree prevents turf from drying = more brown patch. No morning shade. Less brown patch.

  9. BROWN PATCH SYMPTOMS Symptoms of brown patch differ on grasses mowed at low mowing heights (<1 inch) compared to grasses mowed at heights >1 inch.

  10. Among grasses usually mowed at > 1 inch height, tall fescue is the most susceptible to Rhizoctoniasolani in the southeast U.S.

  11. Brown patch on tall fescue – Patches a few inches to 2 or more feet in diameter. Patches often coalesce resulting in large blighted areas To diagnose Brown Patch, look for lesions on leaves at the edges of patches

  12. Lesion caused by R. solani on fescue leaves Hyphae growing between leaf blades Lesions caused by R. solani on fescue leaves. Lesions are gray to brown, irregular in shape, and have a thin brown border. These lesions are the best diagnostic symptom of brown patch on tall fescue.

  13. Brown patch lesion Dollar spot lesion The brown patch fungus and the dollar spot fungus produce irregular foliar lesions with thin brown borders. Note the difference in color of the lesions.

  14. Management of Brown Patch on Tall Fescue

  15. Resistant Cultivars Tall fescue cultivars differ in susceptibility to brown patch

  16. Some cultivars of tall fescue that have exhibited reduced brown patch and high turf quality in the southeast U.S. Reserve Anthem II Crossfire II Safari Apache II Scorpio Coronado Gold Arid 3 Bonsai 2000 Mustang II Helix Wolfpack Tar Heel Jaguar 3 Dominion Genesis

  17. Cultural Control (Environmental Manipulation) leading to suppression of brown patch of tall fescue

  18. Cultural practices that limit severity of brown patch on tall fescue lawns • Maintain mowing height between 2 and 3 inches. • Lower mowing enhances disease. • 2. Avoid nitrogen applications from mid-May to • mid September. Summer N enhances disease. • 3. Decrease shade and increase air circulation. Long • periods of leaf wetness enhance disease. • 4. Avoid irrigation from approximately 2:00 pm • to midnight or later. Turfgrass foliage must be • allowed to dry before nightfall.

  19. Chemical Control of Brown Patch on Tall Fescue

  20. Although there are many fungicides that will provide 2 to 4 weeks control of brown patch on susceptible grasses, lawn care companies can’t afford to return to most properties more frequently than every 5 to 6 weeks. There is no fungicide currently on the market that will consistently provide 6 weeks control of brown patch. However, two fungicides provide acceptable control for 5 weeks…

  21. Fungicides that provide >90% control of brown patch when applied on a 5-week interval Heritage 50WDG 0.2 or 0.4 oz./1000 sq.ft. (azoxystrobin) Prostar 70WP 3.0 oz./1000 sq.ft. (flutolanil)

  22. Fescue lawn in Georgia treated with Heritage (azoxystrobin) at 5-wk-intervals throughout the summer.

  23. Next we will discuss Brown Patch on turf that is usually mowed at a height <1 inch. Creeping bentgrass, perennial ryegrass and annual bluegrass are the most susceptible grasses in this category.

  24. Brown Patch on a bentgrass golf green. Note dark “Smoke-Ring” caused by R. solani mycelium.

  25. The smoke ring, which is visible in the a.m. when the turf is wet, is a good diagnostic sign of brown patch on cool season grasses mowed at a height of <1 inch. Smoke-ring

  26. Smoke-rings may desiccate and disappear when moisture dries from leaf surface.

  27. Occasionally, a smoke-ring may not form, even in the morning. In this case, a sample taken from the edge of a patch, moistened and placed in a plastic bag, may reveal dark gray mycelium after 12-24 hrs of incubation.

  28. Symptoms of brown patch may mimic other diseases or disorders (eg. Take-All patch, dry spots). The ‘plastic bag trick’ can be used to make a positive diagnosis.

  29. Management of Brown Patch on Bentgrass Resistant Species and Cultivars • Creeping bentgrass is more resistant than • colonial bentgrass. • Not much difference in resistance among quality • creeping bentgrass cultivars.

  30. Management of Brown Patch on Bentgrass Cultural Control • Decrease shade and increase air circulation. Use • fans, trim or remove trees and schrubs. • Avoid irrigation in late afternoon and in evening • before midnight. • - Decrease N fertility on high risk areas.

  31. Management of Brown Patch on Bentgrass Chemical Control Contact fungicides – chlorothalonil, mancozeb, thiram, polyoxin – 10 to 14 days control. Localized penetrants – iprodione, vinclozolin, trifloxystrobin, pyraclostrobin – 14 to 21 days control Acropetal penetrants – azoxystrobin, flutolanil, thiophanate-methyl, propiconazole, triadimefon, fenarimol, tetraconazole, triticonazole – 21 to 28 days control

  32. Management of Brown Patch on Bentgrass Chemical Control Preventive fungicide applications for brown patch should begin when night temperatures exceed 60°F for 3-4 consecutive nights. In Georgia, this usually sometime during late May or early June.

  33. Management of Brown Patch on Bentgrass Chemical Control To date, no fungicide resistant strains of R. solani have been detected on turf or other crops. However, it is still a good idea to follow fungicide application practices that will limit the probability of selecting fungicide resistant strains. See Dollar Spot section for review of these practices.

  34. End of Brown Patch Section

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