by Sheila Dunning | Sep 16, 2015
“We have replaced this grass several times over the past few years; and it’s dying again.” I have heard this complaint too many times this summer. Last summer’s heavy rain, the stress of January’s icy weather, and this year’s extended summer have contributed to widespread outbreaks of Take-All Root Rot, a soil-inhabiting fungus Gaeumannomyces graminis var. graminis.
Symptoms of Take-All-Root-Rot. Photo credit: Sheila Dunning, UF/IFAS.
This disease causes yellow grass patches ranging in diameter from a few inches to more than 15 feet. The symptoms first appear in the spring, but the disease can persist all summer and survive the winter. Over time, the entire area dies as the root system rots away. The pathogen is naturally present on warm-season turfgrass roots. High rainfall and stressed turfgrass trigger the disease.
Since the roots are affected, they are not able to efficiently obtain water or nutrients from the soil, nor are they able to store the products of photosynthesis, which result in the loss of color in the leaves. By the time the leaf symptoms appear, the pathogen has been active on the roots for several weeks, probably longer; the disease has been there potentially for years. If the turfgrass is not stressed, leaf symptoms may never be observed.
This disease is very difficult to control once the aboveground symptoms are observed. Measures that prevent or alleviate stress are the best methods for controlling the disease. Any stress (environmental or manmade) placed on the turf weakens it, making it more susceptible to disease. Remember, that every maintenance practice, fertilizer application, and chemical (especially herbicide), application has an impact on turfgrass health. Cultural practices that impact the level of stress experienced by a lawn include:
- proper turfgrass species selection
- mowing at the correct height
- irrigation timing, frequency and volume
- fertilizer: nitrogen and potassium sources and application quantities
- thatch accumulation, and
- soil compaction
The selection of turfgrass species should be based on existing soil pH, sunlight exposure, use of the area and planned maintenance level.
Mower blades must be sharp to avoid tearing of the leaves. Additionally, turfgrasses that are cut below their optimum height become stressed and more susceptible to diseases, especially root rots. When any disease occurs, raise the cutting height. Scalping the grass damages the growing point. Raising the cutting height increases the green plant tissue available for photosynthesis, resulting in more energy for turfgrass growth and subsequent recovery from disease.
If an area of the lawn has an active fungus, washing or blowing off the mower following use will reduce the spread of the disease to unaffected areas.
The amount of water and the timing of its application can prevent or contribute to disease development. Most fungal pathogens that cause leaf diseases require free water (rainfall, irrigation, dew) on the leaf to initiate the infection process. Irrigating every day for a few minutes is not beneficial for the turfgrass because it does not provide enough water to the root zone, but it is beneficial for turfgrass pathogens. It is always best to irrigate when dew is already present, usually between 2 and 8 a.m., and then only apply enough water to wet the root zone of the turfgrass.
Excessively high nitrogen fertility contributes to turfgrass diseases. The minimum amount required for the grass species should be applied. Potassium (K) is an important component in the prevention of diseases, because it prevents plant stress. Application of equal amounts of nitrogen and potassium is recommended for turfgrass health. When turfgrass roots are damaged from disease, it is beneficial to apply nutrients in a liquid solution. However, nitrate-nitrogen increases the severity of diseases, so their use should be avoided when possible. Ammonium-containing fertilizers are the preferred nitrogen sources.
Heavy liming has also been linked to increases in Take-All Root Rot. Since most turfgrasses can tolerate a range of pH, maintaining soil at 5.5 to 6.0 can suppress the development of the pathogen. When the disease is active, frequent foliar applications of small amounts of nutrients is necessary to keep the turfgrass from declining.
Additional maintenance practices that need to be addressed are thatch removal and reduction of soil compaction. Excessive thatch often causes the mower to sink which can result in scalping and reducing the amount of leaf tissue capable of photosynthesizing. Thatch and compacted soil prevent proper drainage, resulting in areas remaining excessively wet, depriving root systems of oxygen. Since recovery of Take-All-Root-Rot damaged turfgrass is often poor, complete renovation of the lawn may be necessary. Removal of all diseased tissue is advised.
As a native soil-inhabiting pathogen, Take-All-Root-Rot cannot be eliminated. However, suppression of the organism through physical removal followed by proper cultivation of the new sod is critical to the establishment of a new lawn. Turfgrass management practices, not chemicals, offer the best control of the disease.
It is acceptable to use fungicides on a preventative basis while rooting in the sod. Azoxystrobin, fenarimol, myclobutanil, propiconazole, pyraclostrobin, thiophate methyl, and triadimefon are all fungicides that can be utilized to prevent disease development while having to excessively irrigate newly laid sod. Ideally, the turf area should be mowed and irrigated prior to a fungicide application. Unless the product needs to be watered in, do not irrigate for at least 24 hours after a chemical treatment. Do not mow for at least 24 hours, to avoid removal of the product attached to the leaf blades.
With all the stresses that our lawns have experienced, it is very important to continue monitoring the turf and be cautious about the cultural practices being used. Take-All Root Rot is likely to flourish. Do not encourage its development. A pathology test with the University of Florida Laboratory can confirm the presence of the disease causing organism. Before resodding again, have the dying sod tested.
For information and the submission form go to:
Sample Submission Guide
For more information on the disease go to:
Take-All-Root-Rot
by Sheila Dunning | Aug 13, 2015
University of Florida researchers maintain a constant vigilance on the potential for mosquito-borne illness concerns. UF/IFAS Florida Medical Entomology Laboratory in Vero Beach tracks rainfall, groundwater levels, mosquito abundance, wild bird populations and virus transmission to animals including horses and sentinel chickens. When mosquito infection rates reach the levels that can infect humans, alerts are sent out. Through the Florida Department of Health, the Centers for Disease Control and Prevention Health Alert Network issues advisories on a weekly basis to those counties at risk. Such an alert was issued for Gadsden, Polk and Walton Counties for the week of July 19-25, 2015. Unfortunately, the first 2015 confirmed human case of West Nile Virus illness in Florida occurred in Walton County shortly thereafter. It was just another reminder for people to take action to reduce their potential for mosquito development in their landscape.
With all the quick afternoon thunderstorms and frequent irrigation events, now is the time to check out where the water is collecting in your yard. The female Culex nigripalpus mosquitoes lay their eggs in temporary flood water pools; even very small ones such as pet watering bowls, bird baths and upturned Magnolia leaves. Dumping out the collection containers every couple of days can greatly reduce the population.
Becoming infected with West Nile Virus is not easy. Mosquitoes usually obtain the virus by feeding on infected wild birds, many of which have migrated from areas that have ongoing West Nile Virus outbreaks. Once the mosquito has drawn infected blood from the bird, the virus goes through a temperature-dependent incubation period within the mosquito. Then, when the infected mosquito “bites” a human or horse the virus mixed in saliva is released into the blood stream of the second host. West Nile Virus is not transmitted from one human to another. Nor is it transmitted from bird to human or from horse to human.
Thanks to a devoted set of researchers and government public health officials, here in Florida we are able to monitor mosquito-borne illnesses quickly and effectively. Additional partners, such as local veterinaries, sentinel bird stations and the Florida Fish and Wildlife Conservation Commission (FWC) serve as reporters for virus population. Should an individual come across dead birds without an obvious cause, reporting them to the FWC at www.myfwc.com/bird/ is the best thing to do.
As for protecting yourself, here are a few pointers:
Stay indoors at dusk (peak mosquito biting time).
If you must be outside, wear long sleeves and pants and/or mosquito repellents containing the active ingredient DEET.
Repair torn door and window screens.
Remove unnecessary outside water sources.
Flush out water collected in outdoor containers every 3-4 days.
Disturb or remove leaf litter, including roof gutters and covers on outdoor equipment.
For additional information, contact your local Extension office about obtaining a free Florida Resident’s Guide to Mosquito Control.
by Sheila Dunning | Jul 7, 2015
There are more than 100 species of plants and animals living in Florida that are in danger of extinction. These trees, flowers, reptiles, amphibians, birds, fish, mammals and invertebrates are listed as either threatened, endangered or species of special concern. As stewards of the land we must question, “What could the loss of a torreya tree, a lupine, a salamander, a butterfly, a woodstork, a right whale, a manatee, a sea turtle or a black bear do to our environment and our quality of life?”
Biological diversity is the variety and variability of species present in an ecosystem including the complex interactions of the many species. Regardless of their size or apparent significance, each species has a role in the circle of life and the food web. Preservation of all species is important. No one knows which ones hold the answers to the future of human existence on this planet.
Many significant developments in medicine have come from obscure plant and animal species. Modern day research includes a vaccine against leprosy being developed because of the nine-banded armadillo and horseshoe crabs being used in developing laboratory tests and finding remedies for several bacterial diseases. In agriculture, genes from wild species may provide the resistance for plant diseases, insects or even weather extremes that could save us from crop failure or possible starvation. There is an interdependence among living things. The extinction of one species may have a domino-like effect on other species. Stability of an ecosystem depends on bio-diversity.
To protect our future and the future of wildlife, the Endangered Species Act became federal law in 1976. This act is intended to protect and promote recovery of plants and animals that are in danger of becoming extinct as a result of human activity. The Environmental Protection Agency is responsible for ensuring the endangered species are protected from pesticides.
Pesticides can kill endangered plants and animals directly or indirectly. Birds mistaking them for food may eat granules, baits or treated seeds. Water contaminated with pesticides ranging in concentrations of less than 0.1 to 1.0 parts per million (ppm) can kill fish. Animals that eat treated crops, drink or wade in contaminated water or feed on tainted prey can be killed indirectly. Some pesticides can build up to lethal levels as predators consume multiple poisoned prey species.
There are certain things you can do to lessen the harmful effects of pesticides on fish and wildlife. Read all pesticide labels carefully to find out whether the use of the product requires special steps to protect endangered species. Determine if the site is designated as the current habitat of an endangered species. Find out this information by visiting http://www.epa.gov/espp/ and http://myfwc.com. When you have a choice of pesticides to use, choose one that is less or non-toxic to fish and wildlife. Read and follow the “Environmental Hazards” section and use the special precautions and measures to minimize harmful effects. Treat only the areas that need to be treated. Leave a buffer zone (untreated area) between bodies of water and treated areas. It is your legal and moral responsibility to protect endangered species by careful use of pesticides in and around their key habitat areas.
Information for this article was derived from University of Florida publications “Pesticide Effects on Nontarget Organisms” by Frederick Fishel and “Applying Pesticides Correctly” by Thomas Dean and Norman Nesheim.
by Sheila Dunning | Jun 23, 2015
Air potato (Dioscores bulbifera) is a perennial, herbaceous self-twining vine that can grow over 60 feet in length, enabling it to climb over and smother many native plants. The Florida Exotic Plant Pest Council (FLEPPC) lists air potato as a Category 1 invasive plant, which means that it has disrupted natural communities and ecological functions by displacing native plant species.
In 2012, a leaf feeding beetle (Lilioceris cheni) was introduced into South Florida from China for biological control of air potato. Although it is too early to determine any potential long-term impacts, the initial results have been promising. The larvae and adults of the air potato leaf beetle feed on the leaf tissue and occasionally the bulbils. The damage to the growing tips of the plant have dramatically reduced its ability to cover native vegetation. Extensive damage to air potato was evident within three months after the first release. Additionally, testing by scientists at the USDA/ARS Invasive Plant Research Laboratory in Fort Lauderdale concluded that the beetle will not complete development on any other plant found in Florida.
The female air potato leaf beetle lays an average of 1,200 eggs, which develop into larvae in about four days. The young beetles skeletonize the air potato leaves for the next eight days and then pupate into foam-like cocoons. Clumps of cocoons fall to the ground and the adult beetles emerge 13 to 16 days later. There can be a new generation of air potato leaf beetle every month while the weather is warm. For the winter, the adults hide in leaf litter and wait for spring.
The question now is: “How well will they survive through a longer, colder Northwest Florida winter?”. USDA scientists, UF Extension agents and citizen scientists in Bay and Okaloosa County hope to find out. Earlier this month, June 2015, air potato leaf beetles from the Hayslip Biological Control and Research and Containment Laboratory in Ft. Pierce were released into areas containing air potato. They will be monitored over the next year. Look for an update next summer.
by Sheila Dunning | May 22, 2015
Everyone with a landscape can make a difference for pollinators. Simply Having Areas Reserved for the Environment enables homeowners, land managers, farmers, individuals, corporations, schools, roadside managers, and golf courses to increase the number of pollinators in the area by making conscious choices to include plants that provide essential habitat for bees, bats, birds, butterflies, moths, beetles, and hummingbirds. What better time than during National Pollinator Week, June 15-21, 2015.
Initiated and managed by the North American Pollinator Protection Campaign, National Pollinator Week was unanimously approved and designated by the U.S. Senate in 2007. Each year since, the U.S. Secretary of Agriculture has signed the proclamation in an effort to address the urgent issue of declining pollinator populations.
Worldwide there is evidence that pollinating animals have suffered from loss of habitat, pesticide misuse, competition from invasive species, disease, and parasites. Many pollinators are federally “listed species”, meaning that there is documented information confirming the disappearance and/or significant population reduction in natural areas. The United States has lost over 50% of its managed honeybee colonies over the past ten years. The European Union has been so concerned that they invested over $20 million investigating the status of pollinators in Europe.
Pollinator health affects everyone. Worldwide, roughly 1,000 plants grown for food, beverages, fibers, spices, and medicines need to be pollinated by animals in order to produce the goods on which we depend. Food and beverages produced with the help of pollinators include: apples, blueberries, chocolate, coffee, melons, peaches, potatoes, pumpkins, vanilla, almonds, and tequila. In the U.S., pollination by honey bees, native bees, and other insects produces $40 billion worth of products annually.
The native plants that can be identified and preserved or introduced include trees, shrubs, vines and perennials. Some of them include: Eastern Redbud (Cercis canadensis), Highbush Blueberry (Vaccinium spp.), Passionflower (Passiflora spp.), Coreopsis (Coreopsis spp.), Goldenrod (Solidago spp.), Black-eyed Susan (Rudbeckia hirta), and Butterfly Milkweed (Asclepias tuberosa). Simply identifying and avoiding damaging many of the existing native plants will allow anyone to provide important homes and food for many different pollinating animals. During National Pollinator Week S.H.A.R.E. your space.
For additional information:
UF Native Buzz
Gardening for Pollinators
Minimizing Honey Bee Exposure to Pesticides
The Xerces Society
