It usually begins and appears as small patches in your lawn, about 10”-18” in diameter, turning from green to yellow, then to brown. “Brown patch” (Rhizoctonia blight ) takes on a straw colored appearance as the blades of affected grass die.
From now through May homeowners and property managers should be on the look-out for “brown patch”. It is commonly observed from the end of fall, through the winter months and typically fading away by spring. It can affect all warm season turf grasses, two of which happen to be the most popular in South Florida, St. Augustine and Zoysia grass.
There are over 100,000 species of fungi in our world and more than 8000 of them are found to cause disease in plants and grasses. Many fungi are not harmful and in fact necessary and beneficial. Beneficial soil based fungi are what help our plants and trees to grow. They aid in the uptake of nutrients and minerals through root systems and are critically important to the process of decomposing dead organic matter, including plant, tree and palm residue.
Rhizoctonia is a soil based fungus that becomes active regardless of how well you maintain your lawn and landscaping. Infection this time of year is triggered by the combination of cool temperatures (below 80F), extended exposure to high humidity and/or rainfall, as well as, overwatering from irrigation systems. The management of how often your sprinklers run and how long they run for is extremely important and requires coordination between a homeowner and those who provide lawn and landscaping care services.
Homeowners should keep in mind, the evaluation and diagnosis of sprinkler system problems is not something included in most lawn/landscaping healthcare programs. Irrigation systems should be inspected and maintained at least twice per year by a professional. The time of day, the length of running time and the frequency will need to change throughout the year. All are dependent upon the specific needs of each property (type of soil, type of plants/trees), current weather and considerations of County imposed watering restrictions.
Many lawn/landscaping care providers have also been accused of “burning” the lawn with weed killer or fertilizer. This is almost never the case. If an herbicide (weed killer) is the cause it will generally affect much more than one small patch of lawn and only turns the blades brown, it does not “rot” the leaf base. Plus, if the cause is fungal the leaf base will omit a distinct rotten odor. This does not occur from herbicide. Most professional lawn and landscaping healthcare providers use slow release fertilizers which are incapable of burning a single spot within a lawn surface.
Cultural conditions and water management are the important considerations in triggering this disease. Being familiar with the signs and symptoms and early intervention are the best ammunition for dealing with an outbreak. Specific fungicides can be applied to the affected area and are very effective, however, since this disease is active in the time of year when our grass is in its slowest growth phase, recovery is an extremely slow process. Fungicide only stops the disease from spreading, it does not and cannot promote new grass growth. The brown patch will only disappear after the dead turf decomposes and is slowly replaced by new growth. That can take weeks at best and sometimes months.
So as not to upset the balance between beneficial fungi and potentially harmful fungi, preventative application of fungicide is not recommended unless the disease has been a routine occurrence, in a specific location.
Don’t be tempted to play the blame game. Fungus happens!
Rick Barocas is a Certified Arborist and Manager of the Tree Division at One Two Tree/Pest Free.