02 Jul Lethal Viral Necrosis in Florida Home Lawns
Lethal Viral Necrosis in Florida Home Lawns
An abundance of Florida home lawns are experiencing an outbreak of turfgrass disease with symptoms including yellowing grass blades, brown roots and dying grass. This is especially prevalent in Floratam St. Augustine home lawns, which is one of the most popular grass types found throughout Florida yards. However, LVN can s till affect other St. Augustine grasses. After genome (genetic) testing, researchers have found many samples to contain a viral disease that causes the decline in turfgrass health and eventually death called Lethal Viral Necrosis (LVN).
LVN outbreaks start as another disease: Sugarcane Mosaic Virus (SCMV). SCMV has the capability to infect various grass types including St. Augustine grass, zoysia, bermuda grass, some paspalum varieties, certain breeds of crabgrass, crop grasses or maize, but it only progresses to Lethal Viral Necrosis (LVN) in Floratam St. Augustine, which can be detrimental to an entire lawn. Symptoms of SCMV are a yellow, mosaic-looking pattern.
Preparing yourself ahead of time by understanding what SCMV and LVN are and being able to identify outbreaks are the first steps for keeping it away from you. After that, you can begin coming up with prevention and treatment strategies (for SCMV). Treatment strategies will only be applicable to lawns with SCMV as lawns with LVN cannot be treated. LVN will kill lawns 100 percent of the time, but it only progresses to Lethal Viral Necrosis (LVN) in certain varieties of St. Augustine, which can be detrimental to an entire lawn. Currently, Palmetto is the most widely recommended St. Augustine grass replacement cultivar for lawns and landscapes impacted by LVN.
What is Lethal Viral Necrosis?
LVN is a viral disease that infects the leaves and roots in Floratam St. Augustine. Symptoms include the yellowing of grass blades that create a mosaic-like pattern that becomes 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 spread and lead to the death of turfgrass, which has the potential to destroy an entire front and backyard.
What’s the difference between Lethal Viral Necrosis and Sugarcane Mosaic Virus?
LVN always starts as SCMV as they are both caused by the same virus, however, turfgrass can develop SCMV without ever developing LVN. SCMV makes grass more susceptible to disease, meaning the grass becomes more vulnerable to disease outbreaks once it has been weakened by SCMV; SCMV doesn’t directly cause LVN. When SCMV takes over turfgrass, death of the turfgrass is always caused by LVN—not SCMV—and every confirmed case of LVN also tests positive for SCMV.
Both LVN and SCMV are viral diseases, so typical fungicide applications for fungal diseases don’t have the capability to treat it. 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 SCMV looks like compared to LVN.
Pictured above: Sugarcane Mosaic Virus (SCMV) 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 is spreading across Floratam home lawns 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 2014. 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 a plant, however, LVN spreads through exposed grass sap. This mostly occurs when grass is freshly cut and the blade is left open. Wheels from equipment like lawn mowers, or even trimmers transmit the disease across lawns and grind the disease into other grass blades. 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 can only spread once it is inside a new plant. The virus is no longer 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 irrigation, soil or the air.
How do I identify LVN?
LVN can be spotted with symptoms including general chlorosis with yellow streaks along the blades that becomes necrotic over time as seen in the previous image comparison of SCMV 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.
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 baggie-like bag to:
Plant Clinic – Tropical Research and Education Center
Att. Dr. Romina Gazis
18905 S.W. 280 Street
Homestead, FL 33031
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 Disease Lab in Gainesville: https://turf.ifas.ufl.edu/rapiddiag.shtml. 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 cut 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 is 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.
If you have SCMV that hasn’t quite reached the LVN stage, keep the grass warm and it won’t transition. Lower temperatures trigger the transition from SCMV to LVN. Manage it as best as you can to help delay it, 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 lawn will eventually die.
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. There are a few things you can do to delay the death such as keeping the grass warm and managing it as best as you can with proper maintenance, but it will die as time goes by.
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. 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. Make it weed free prior to sodding. 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. Add compost if there isn’t enough organic matter and rake it into your soil.
What are the best replacement grasses for a lawn that was killed by Lethal Viral Necrosis?
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. They are a huge nuisance in Florida and they love St. Augustine grass. Overtime, Floratam’s resistance to the chinch bug declined. Zoysia is a Floratam replacement, but from a contractor’s perspective, it costs more to maintain that than it does for standard practice for Floratam or other St. Augustine options.
Palmetto® St. Augustine has been recognized by the University of Florida as the only LVN resistant turfgrass. The University of Florida used to also recognize Bitterblue as a LVN resistant turfgrass, but due to a lack of good plant stock, the University of Florida no longer recognizes it. Lawns that have been re-sodded with Palmetto after an LVN outbreak are surviving. 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.
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.
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.
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