Lethal Viral Necrosis in Florida Home Lawns

Many Florida home lawns are experiencing an outbreak of a viral turfgrass disease that can destroy entire lawns and sometimes those surrounding it within three years of infection or less. This is especially prevalent in Floratam St. Augustine home lawns, which is the most popular grass type found throughout South Florida yards. The disease was first verified in Palm Beach County in 2014. However, it has now spread throughout South Florida and continues to expand into other regions of the state. After genome (genetic) testing, researchers have found the problem is a viral condition that causes the decline in turfgrass health and eventually death called Lethal Viral Necrosis (LVN).

It’s important to note that LVN outbreaks starts from a disease: mosaic disease caused by Sugarcane Mosaic Virus (SCMV). SCMV has the capability to infect various grass types including but not limited to St. Augustine, zoysia and bermuda grass cultivars. SCMV also has the capability to infect some paspalum varieties, certain breeds of crabgrass, crop grasses or maize, but so far it only progresses to Lethal Viral Necrosis (LVN) in Floratam St. Augustine. Other grass types like the ones listed can be infected by SCMV but do not develop LVN.

Preparing yourself by understanding SCMV and LVN are the first steps for keeping the viral disease away from your home lawn. After that, you can begin coming up with prevention and treatment strategies (for SCMV specifically). Treatment strategies will only be applicable to lawns with mosaic as lawns with LVN cannot be treated. LVN will kill lawns 100 percent of the time, but SCMV only causes Lethal Viral Necrosis (LVN) in Floratam St. Augustine. This disease cannot be treated with any fungicide or pesticide. Prevention with proper sanitation and the overall replacement with other turfgrasses are currently the only ways of dealing with LVN in residential and commercial landscapes. 

Currently, researchers and turfgrass experts alike recommend Palmetto® St. Augustine as a St. Augustine grass replacement cultivar for Floratam lawns and commercial landscapes impacted by LVN. CitraBlue® St. Augustine is another turfgrass option introduced by the University of Florida. Although CitraBlue is in its final stages of evaluation, it’s not yet ready to be recommended as resistant to LVN. Bitterblue St. Augustine is an older cultivar and is no longer recommended due to its uncertain cultivar genetic makeup, which may include Floratam.

What is Lethal Viral Necrosis?

LVN is a systemic viral condition that infects the leaves and roots in Floratam St. Augustine. Symptoms include the yellowing of grass blades that create a mosaic-like pattern and become necrotic over time. According to the University of Florida’s Institute of Food and Agricultural Sciences, LVN symptoms look like “blotchy and streaky patterns of yellow and green color. In fact, turfgrass tends to have broken yellow streaks running between the veins on an otherwise green blade.” These symptoms will eventually cause Floratam St. Augustine grass blades to turn brown, spread and lead to the early death of the turfgrass.

What’s the difference between Lethal Viral Necrosis and Mosaic Disease?

LVN and mosaic disease are both caused by SCMV as SCMV is the causal pathogen, however, turfgrass cultivars other than Floratam develop mosaic disease without ever progressing to LVN. In Floratam, mosaic typically progresses to LVN and lawns die. SCMV also makes grass more susceptible to other diseases and stressors. When SCMV infects turfgrass and leads to death of the turfgrass, this is always caused by LVN—not mosaic—and every confirmed case of LVN also tests positive for SCMV, but not every SCMV infection results in death of turf.

Both LVN and mosaic disease are initiated by a virus, so typical fungicide applications for fungal diseases don’t have the capability to treat it. With that being said, viral diseases are not all that common in comparison to fungal diseases like dollar spot, large or brown patch, fairy ring, etc. Below are two images demonstrating what mosaic disease looks like compared to LVN. LVN always starts out with mosaic symptoms: blotchy and streaky patterns of yellow and green color. Overtime, mosaic typically progresses to LVN in Floratam as grass blades turn brown and die, or become necrotic, while other varieties continue to have mild mosaic symptoms.

Pictured above: Mosaic disease in St. Augustine grass.

Pictured above: Lethal Viral Necrosis (LVN) in Floratam St. Augustine grass.

Where has the virus been spotted?

Currently, SCMV in particular has been identified in home lawns and commercial landscapes located in the state of Florida and spreading. SCMV has a patchy distribution around Florida as seen in the map below, however, most of it has been spotted around the southern areas of the state. SCMV was initially spotted in Pinellas County throughout hundreds of affected lawns that started to die in 2013. An outbreak then occurred in Palm Beach County and then spread to neighboring counties around it. Most of the LVN sightings are located throughout the southern part of the state.

How does LVN spread?

The virus is able to multiply only once it is inside the system of a plant, however, LVN spreads through exposed grass sap. This mostly occurs when grass is freshly mowed and the blade is left open. Wheels from equipment like lawn mowers transmit the disease across lawns and pass the disease into other exposed grass blades. Trimmers not only increase the damage to the grass and release sap, but transmit the virus as well. Moving any newly mowed plant material transmits the virus to different locations.

When lawns are wet, it increases the likelihood of the disease transmitting. The virus is less likely to be transmitted when grass is dry and it doesn’t stay alive long when it’s located outside of the plant’s system, in a dead plant or in dried out plant parts. It does not affect ornamentals, pets, people, wildlife or palms—only Floratam St. Augustine. LVN can not be spread by soil or the air. Irrigation and aphids can spread it, but they are not likely to do so.

How do I identify LVN?

Mosaic disease can be spotted with symptoms including general chlorosis with yellow streaks along the blades. When it becomes necrotic in early winter as temperatures drop below 64 degrees Fahrenheit, the disease has progressed to LVN as seen in the previous image comparison of mosaic disease and LVN. LVN is often mistaken for herbicide damage, take-all root rot or chinch bugs. Below is what an LVN-affected lawn may look like from a distance.

It typically takes about three years or less for LVN infected Floratam to die. The first detection of LVN can take place in year one with localized patches of brown grass. In year two, the patches begin to expand, become more numerous and weeds start to invade as there’s less competition with living grass for sunlight or other nutrients. The widespread loss of Floratam in the first infected lawns tends to occur during year three.

Pictured above: A Floratam St. Augustine lawn affected by LVN in Florida.

The best way to accurately identify LVN is by getting a correct diagnosis and sending in a sample to your local extension agency or land grant university. So far, LVN has only been spotted in the state of Florida, so samples can be sent as a sod plug that’s at least four or five inches across and a couple of inches deep into the affected turfgrass. It should be noted that when sending a sample, the grass needs to be affected, but not dead. Ship an over-night sample in a sandwich bag to one of the two locations:

Be sure to shake the soil off of the samples as much as possible before sending. Sending samples earlier in the week will prevent them from sitting over the weekend. The specimen submittal form is available at: https://trec.ifas.ufl.edu/media/trecifasufledu/highlights-icons-100×80/TREC-CLINIC-ENGLISHFORM-2018.pdf. Attached photos are welcome and encouraged. Samples can also be sent to the Rapid Turf Diagnostic Service in Gainesville. Be sure to contact your local extension office if you have a suspected site.

How do I prevent LVN?

As previously noted, LVN spreads through exposed plant sap, which is why recently trimmed or mowed grass promotes the spread of the virus. Wheels from equipment like lawn mowers, or even trimmers transmit the disease across lawns. When lawns are wet, it increases the likelihood of the disease transmitting. The virus is no longer transmitted when grass is dry. Consider not mowing the lawn when the grass is wet or after rainfall if you’ve noticed lawns that look like they’ve been affected by LVN in your area. SCMV only progresses to LVN in Floratam St. Augustine lawns.

If you use your neighbor’s mower or let a neighbor use your mower, allow sap to dry on equipment. This tip can also be applied if you have a lawn care specialist mowing your lawn. It’s recommended you sanitize mowers and other equipment with sanitizers like Virkon S at 2 percent, GreenShield, PineSol, various alcohols, Physan 20 or Lysol. Household bleach will also kill the virus, but it can corrode any metal equipment. If you notice disease in your lawn, refrain from mowing it until you can accurately identify the disease.

Lower temperatures trigger the transition from mosaic disease to LVN. Manage it as best as you can to help delay damage, but the delay won’t last much longer than three years afterwards. It will die 95 percent of the time. It’ll show signs of infection in summer and weeds will become a big problem.

How do I treat Lethal Viral Necrosis?

You don’t. Once you have a confirmed LVN diagnosis, your Floratam lawn will eventually die, leaving behind weeds and any other non-Floratam grasses.

What are the next steps after confirming LVN in my lawn?

If you have sent a sample in to your local land grant university or had a professional diagnose your Floratam lawn with LVN, it will eventually die. LVN is a viral disease that can’t be treated with fungicides.

The biggest recommendation is to refrain from re-sodding your lawn with Floratam St. Augustine again. Install a grass that has been recognized as a LVN resistant variety such as Palmetto St. Augustine. See the next section below for recommendations on new grass types.

With that being said, you don’t get the opportunity to re-do your lawn very often, so do it right. Before installation takes place, strip the old grass completely and start fresh with a sod cutter. Don’t grade the lawn with soil. The soil in an LVN infected lawn is not infected—only the grass is infected. There is no need to remove the current soil. Collect and submit a soil analysis to find out which nutrients are currently in your soil and which ones are not so that you can promote a new, healthy lawn. Afterwards, use glyphosate or a non-selective alternative to glyphosate to kill any currently living grass or weeds. It should be noted that non-selective herbicides like glyphosate will affect the soil pH. Collect and submit a soil analysis before the use of other chemicals. Add compost if there isn’t enough organic matter and rake it into your soil.

Once the grass has been installed, conduct a simple irrigation audit to make sure your lawn is receiving the right amount of water in all the different areas of your yard. These practices will ensure you start your new lawn off on the right foot. Learn more in our sod installation guide.

What are the best replacement grasses for a lawn that was killed by Lethal Viral Necrosis?

LVN infected Floratam St. Augustine that’s later replaced with new Floratam sod will become reinfected and die again. Newly laid Floratam tends to die within just a few months after installation—a much faster rate than LVN infected established Floratam. A lot of homeowners want to completely deviate from St. Augustine after this experience and choose to install zoysia grass instead. EMPIRE® Zoysia is a chinch bug resistant option that truly thrives in Florida. Floratam was highly sought after in the state of Florida because of its original resistance to chinch bugs, which are insects that can also completely ruin a lawn. Unfortunately, they are a huge nuisance in Florida and they also happen to love feeding on St. Augustine grass. Overtime, Floratam’s resistance to the chinch bug declined.

Bitterblue, Seville, Raleigh, Classic, CitraBlue and Palmetto are options that serve as suitable replacements for Floratam in LVN sites, however, the University of Florida only recommends Palmetto St. Augustine and CitraBlue St. Augustine at this time. Palmetto® St. Augustine has been recognized by the University of Florida as the only LVN resistant turfgrass. Palmetto is also an established variety that’s sold over two billion sq. ft. and has been found to have genetic purity. Lawns that have been re-sodded with Palmetto after an LVN outbreak are surviving. Although they can become infected, mosaic symptoms are mild. Sod Solutions has launched the Genuine Palmetto campaign to help homeowners impacted by LVN. When purchasing Palmetto, you will need to be wary of unscrupulous parties selling other St. Augustine grasses and representing it as Palmetto. If you would like to be sure you are getting the real thing, visit GenuinePalmetto.com.

A newly released St. Augustine, CitraBlue®, is still undergoing testing and research, but shows promising results of demonstrating resistance to LVN after four years of research in LVN infected sites.

It’s recommended that when making the choice to install new sod, you select a managed, proprietary turfgrass that maintains genetic purity. This ensures you’re installing what you pay for and don’t go through another LVN outbreak. Bitterblue, for example, is not a managed, proprietary turfgrass. A lot of homeowners may purchase Bitterblue, but due to contamination, there’s not a real way of knowing if you are in fact installing a genetically pure variety of Bitterblue. Find a genetically pure, proprietary turfgrass at GenuinePalmetto.com.

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Pictured above from left to right: A before shot of a Floratam St. Augustine lawn in Florida that was affected by LVN and an after shot of the same lawn once it was re-sodded with CitraBlue St. Augustine.

Sources:

• Lethal Viral Necrosis of St. Augustinegrass in Palm Beach County, Florida: https://discover.pbcgov.org/coextension/horticulture/pages/lethal-necrosis.aspx
• CitraBlue as a Lethal Viral Necrosis Replacement Turf: Consider This…: https://blogs.ifas.ufl.edu/palmbeachco/2021/01/21/citrablue-as-a-lethal-viral-necrosis-replacement-turf-consider-this/
• Lethal Viral Necrosis of Floratam St. Augustinegrass: Also Called Sugarcane Mosaic Virus: https://blogs.ifas.ufl.edu/palmbeachco/2018/01/19/mosaic-disease-threat-floratam-lawns/
• Lethal Viral Necrosis (associated with Sugarcane Mosaic Virus-SCMV) frequently asked questions: https://blogs.ifas.ufl.edu/miamidadeco/2019/01/14/lethal-viral-necrosis-associated-with-sugarcane-mosaic-virus-scmv-frequently-asked-questions/