''Magnaporthe poae'' is an

ascomycete Ascomycota is a phylum of the kingdom Fungi that, together with the Basidiomycota, forms the subkingdom Dikarya. Its members are commonly known as the sac fungi or ascomycetes. It is the largest phylum of Fungi, with over 64,000 species. The defi ...

fungus which causes the turfgrass disease commonly known as summer patch, or Poa patch. Cornell University Fact Sheet
/ref> The disease occurs mostly on

Kentucky bluegrass ''Poa pratensis'', commonly known as Kentucky bluegrass (or blue grass), smooth meadow-grass, or common meadow-grass, is a perennial species of grass native to practically all of Europe, North Asia and the mountains of Algeria and Morocco. Altho ...

''(Poa pratensis)'',

Fescues ''Festuca'' (fescue) is a genus of flowering plants belonging to the grass family Poaceae (subfamily Pooideae). They are evergreen or herbaceous perennial tufted grasses with a height range of and a cosmopolitan distribution, occurring on every ...

''(Festuca sp.),'' and on Annual bluegrass ''(Poa annua).''Penn State Turfgrass
/ref>

Bentgrass ''Agrostis'' (bent or bentgrass) is a large and very nearly cosmopolitan genus of plants in the grass family, found in nearly all the countries in the world. It has been bred as a GMO creeping bent grass. Species * '' Agrostis aequivalvi'' ...

(Agrostis sp.) may also become infected but shows very few symptoms and quickly recovers. Summer Patch will usually become noticeable between June and September, although small signs can appear at any time but are not noticeable because the turfgrass can recover quickly.

Symptoms

Symptoms of summer patch appear very similar to necrotic ring spot. This makes it very difficult to identify; if correct diagnosis is critical contact a local cooperative extension program or a qualified commercial lab. Although it is difficult to identify alone, if one takes into account grass species and cultural practices a trained eye can diagnose summer patch. Summer patch will appear as irregular patches, rings (less than 10 inches in diameter), and crescents. The "frog eye" appearance is often from the ''Poa annua'' being killed by the fungus while the middle living grass is Bentgrass. On lower cut turf, typically lower than 1.4 inches, summer patch is much easier to identify. A tug test can be performed and look for blackened roots. Yellowing and decline is often found on ''Poa annua'' in a mixed bentgrass area.

Disease cycle

Summer patch is usually caused by an interaction of environmental factors (stress) and a root or crown rot caused by ''Magnaporthe poae''. The fungus ''Magnaporthe poae'' is consistently found in grass roots but does not become noticeable until conditions are favorable. Favorable conditions include extended periods of humid weather and daytime high temperatures usually (greater than 82 °F) in midsummer. Other causes include: poor air circulation, high soil moisture (sometimes caused by frequent irrigation), soil compaction (heavy traffic), and poor drainage. The disease does not appear noticeable during the cool weather of spring and fall. Summer patch seems to favor soil with a pH higher than 6.

Cultural control

The best way to prevent and minimize summer patch damage is by using disease-resistant turfgrass species/cultivars. To find these new cultivars one can visit turfgrass seed distributors, extension specialists, or visit the National Turfgrass Evaluation Program website at: http://www.ntep.org. Ohio State Fact Sheet
If incorporating disease resistant varieties of turfgrass is not an option, then focus on better management practices. These practices should help promote adequate drainage, reduce soil compaction, and a balanced fertility program. Install an internal drainage system if you have severe drainage problems. An adequate aeration program will relieve compaction and improve drainage.

Aeration Aeration (also called aerification or aeriation) is the Systems engineering process, process by which air is circulated through, mixed with or solvation, dissolved in a liquid or other substances that act as a fluid (such as soil). Aeration proces ...

should annually disrupt between 15–20% of the total surface area. Avoid using quick-release fertilizers; try using slow-release ammonium sources. If the soil pH is above 6, then use

ammonium sulfate Ammonium sulfate (American English and international scientific usage; ammonium sulphate in British English); (NH4)2SO4, is an inorganic salt with a number of commercial uses. The most common use is as a soil fertilizer. It contains 21% nitrogen a ...

, which will acidify the soil. Turfgrass has been shown to be most resistant to summer patch when soil pH is between 5.5 and 6. Most balanced fertility programs for Kentucky Bluegrass lawns will consist of applying two to five lbs of nitrogen/1000 sq.ft. a year. Promote root growth by watering heavy and infrequently. Since low mowing heights are conducive to shallow rooting, raising the height of cut can possibly result in less summer patch injury.

Chemical control

If severe enough or on high valued turf (golf greens) summer patch can be controlled with the use of

fungicides Fungicides are biocidal chemical compounds or biological organisms used to kill parasitic fungi or their spores. A fungistatic inhibits their growth. Fungi can cause serious damage in agriculture, resulting in critical losses of yield, quality, ...

. Applications are made on a preventive basis and usually applied 3–4 weeks before symptoms appear. High water amounts should be used, about 5–10 gallons per . Effective fungicides include: *Benzimidazoles: Cleary 3336, Fungo 50, T Storm *DMIs: Banner, Bayleton, Eagle, Rubigan, Lynx, Spectator, Trinity *Strobilurins: Compass, Disarm, Heritage, Insignia

References

{{DEFAULTSORT:Summer Patch Fungi described in 1989 Fungi of North America Magnaporthales Turfgrass diseases