Today is June 23, 2010.  The temperatures have been in the mid 90’s for about 2 weeks and it has been raining in the afternoon around the city with the hit or miss thunderstorms that are typical in this region in early summer.  In May it was in the mid 80’s with even more rain.  It is hot and humid, a very typical southern summer.  Last year and the year before, we were in a level 4 and level 5 drought in Atlanta, Georgia.  This year, thankfully, the drought is over.

The Brown Patch Fungus Is Always Present

I give you these details to help explain why the fescue lawns, in Atlanta this year, are suffering from brown patch fungus.  The conditions are ideal right now for brown patch fungus in tall fescue lawns.  When we were in a drought the fescue lawns went into a semi-dormant state.  There was less moisture in the air to allow the disease to spread.  The fungus that causes brown patch is constantly present in the lawn.  It can not be eliminated.  When conditions are right and your turf is weak the fungus takes off. 

Why Does The Brown Patch Show Up Now?

Your fescue is weak during the summer.  Why?  Because it is a cool season grass and when it is in the 80’s and 90’s it is stressed from the heat.   The best thing you can do is not water during the evening and mow at the highest setting.  Actually when it is this hot out, it is best to limit watering to one or two times a week for about 15 minutes each at 5a.m. – 6a.m.   This is just to try to keep some water on the lawn so it does not dry out entirely but if the weather persists and gets to a drought type pattern it is best to just shut down watering all together.  We are still in some watering restrictions and probably always will be and watering is not going to produce good results anyway so save your money. 

Can It Be Treated 

Walter Reeves talks about Brown Patch

Walter Reeves is a well known expert in lawn and shrub care for the Southeast.  He has a very detailed article about the specifics of brown patch fungus in Tall Fescue.

Fungicide treatments can be effective on minimizing Brown Patch Fungus but they need to be applied at an interval of about 2 week periods.  This can be costly.  The fungicides can cost about $20 per 1000 square feet.  For a typical lawn size of 5000 square feet that is about $100 every 2 weeks. 

We actually use a product that costs a bit less then the numbers that Walter Reeves was quoting.  It is very effective at controlling brown patch but it does need to be applied every 2 weeks when conditions are favorable for the disease. 

You can purchase this product here.

Cultural Practices To Minimize Brown Patch Fungus In Tall Fescue

Cultural practices play a big role on the development of brown patch.  Nitrogen fertilization, irrigation, and mowing are the most important factors to consider. For best results, tall fescue should be mowed at heights between 2.5 and 3.5 inches. Brown patch activity can be encouraged when mowing heights are either too low or too high. Mowing heights below 2.5" increase brown patch development by reducing the tall fescue plant’s ability to produce energy.  Mowing heights higher than 3.5" create a turf canopy that is dense, matted, and holds moisture for extended periods of time

How Our Service Handles Brown Patch Fungus

Obviously brown patch is a difficult problem to deal with in the southern heat on fescue lawns.  When conditions are right, everyone gets it at the same time.  

We do treat with a fungicide that will minimize the fungus for about 2 weeks.  Just as Walter Reeves has discussed.  We will charge an extra application fee for this treatment.  So whatever your application fee is for your lawn will be the charge of the fungicide treatment.  You tell us how many you would like to have and we will put you into our special fungicide route for treatments.  This fee will usually be much less then Walter Reeves has suggested as a treatment pricing for fungicide treatments. 

The good news is the brown patch is only active during high humid periods when temperatures are in the high 80’s – low 90’s.  Once temps get up into the high 90’s the fescue actually goes into a more dormant state. 

Fall seeding is a must to replenish what fescue is lost during the summer heat stress.  Call the office to get put on the fall seeding schedule now so you don’t have to worry about it later.

Figure 1: Leaf lesions caused by Rhizoctonia sp. (provided by Dr. Eric B. Nelson, Cornell University)

Figure 2: Microscopic view of Rhizoctonia sp. mycelium. (provided by Dr. Eric B. Nelson, Cornell University)

Symptoms

The pattern of symptoms depends largely on cool vs. warm season grasses, mowing practices, and moisture levels. On cool season grasses the symptoms produced by a Rhizoctonia sp. infection may vary depending on the maintenance practices. Under close mowing conditions, cool season grasses that are kept very wet produce small to 50 cm blighted patches that appear quickly during optimum conditions. The patches may contain the diagnostic feature of a purplish-gray border that is referred to as a "smoke-ring". The smoke-ring is commonly missing from the symptomatic region but if present is most often observed during hot-humid weather and is most easily seen when a dew is present. Cool season grasses that are cut higher produce small light brown patches up to 15 cm in diameter that may or may not contain that diagnostic smoke-ring symptom. Cool season grasses that are cut high and kept dry may produce patches up to 30 cm in diameter. These patches may produce a symptomatic patch known as a "frogeye". Frogeye patches have apparently healthy green grass surrounded by a ring of necrotic grass that appears very flat and sunken into the ground.

Individual leaf lesions may be small, round to irregularly shaped, and tan in color with a distinctive dark brown margin (Fig. 1). As the fungus grows, the hyphae produce a characteristic branching pattern of 90° angles that are easily recognized microscopically. The width of the hypha decreases at the junction of a branch giving it a pinched appearance (Fig. 2).

Disease Cycle
Rhizoctonia spp. produce structures referred to as "bulbils" to survive unfavorable conditions such as freezing temperatures or drought. The optimum temperature range for germination of the fungus is from 21°C to 32^°C (70°F to 90^°F). The pathogen mainly infects leaves and sheaths of the turfgrass plant.

Brown patch disease cycle.
(image from The Compendium of Turfgrass Diseases, APS Press)