Jennifer Pelham
Extension Services

It seems like a few months ago we were hoping for rain, but now we just hope that it will stop – at least for a day or two.  The plants in our landscape need water in order to survive, but there is a limit.  Too much rain can be detrimental.  With all the rain we have had the past few weeks, many plants are suffering.  One plant that is definitely showing its distress is the lawn.
Too much water in the lawn can lead to many problems.  It causes it to become stressed because it is no longer growing under ideal conditions.  Trying to adapt to environmental stresses, weakens the lawn, making it susceptible to pests, such as insects, weeds and diseases.  With too much water, diseases are one of the main pests that invade the lawn.
Diseases can be difficult to understand.  They are caused by biological pathogens that are rarely seen.  An interaction between the plant and pathogen, diseases disrupt the normal growth habit and appearance of the plant.  Most of the diseases that attack the lawn are caused by fungi.  The fungi are always in the soil.  They lay dormant until they are given the right environment, such as soggy soils and wet leaves, to multiply.  
The excessive rainfall we have been experiencing in Central Florida is causing our lawns to become stressed and susceptible to attacks from the dormant fungi.  The perfect environment is being created for disease infestations.  Unfortunately we cannot monitor diseases, like insects or weeds, until we see the symptoms.  
The symptoms will appear in two common patterns on the lawn, either in a circular patch of browning turf or as spots on the leaves.  Remember, though, that many lawn problems have similar symptoms, so a positive identification of the problem is needed in order to achieve a successful control.
Once a disease is identified, it should be controlled to prevent it from spreading.  The first step is to find out why the disease has attacked the lawn in the first place.  What caused the lawn to be weakened?  It could be nutritional deficiencies, cold weather, drought, or excessive rainfall.  If you are experiencing disease in your lawn now, it is probably due to the latter – excessive rainfall.  
Correcting the cultural requirements, what caused the weakened plant, should be the next step, although sometimes that is not possible.  We have no control over the amount of rain we’ve been getting the past few weeks.  However, with proper cultural practices disease in lawns can be controlled and prevented.  This includes mowing with a sharp blade, mowing at the correct height (3-4 inches), using proper fertilization rates, and managing the water requirements of the lawn.
If correcting the cultural requirements of the lawn is not possible at the time, chemical control will be required.  A fungicide will need to be applied.  Fungicides will not eliminate or kill the pathogens in the lawn, but will suppress and slow down the growth and reproduction of the fungus.  Hence, the fungicide will cause the fungus to go dormant again until the right environment comes along again.  Therefore, once the fungus is suppressed, corrections need to be made to the cultural requirements of the lawn in order to prevent the fungus from attacking again.
It is important to only use fungicides when absolutely necessary.  The overuse of any pesticide can cause the development of pesticide-resistant pests.  Spot treatment, only applying the fungicide in the affected area, is best.  If the disease is located on one site, it does not mean that the disease will occur in other areas.  Many small “microenvironments”, influenced by trees, buildings, and elevation can be located on one single lot.
Always follow the directions on the label of any pesticide you use.  Using more of the recommended rate will not increase the effectiveness of the product.  It will just waste your money and add additional pollutants into the environment.  Use pesticides safely and wisely.  
Keep an eye out in your lawn for disease problems and correct them before they spread.  If you are unsure that a fungus is causing your lawn problem, please contact the Osceola County Extension for proper identification before applying any pesticides.
If you would like more information on lawn diseases or have other plant questions, the Osceola County Master Gardeners are available to take your calls on Monday thru Friday from 9 a.m. to 3 p.m.  Call 321-697-3000.
Jennifer Pelham is a horticulture agent with the University of Florida/IFAS Osceola County Extension office.