"With the TC50 cooling mechanism, the temperature can be lowered by about 6 * C". "UV-C light has the ability to alter the DNA of fungal spores, such as the gray leaf spot"
How to prevent gray leaf spot?
The summer of 2020 was a quick one to forget for many. Extreme droughts, extreme temperatures, and a short transition period to the 20/21 season put a lot of stress on the plant (and gardeners). These were conditions in which diseases thrive, creating a situation that keeps us awake at night. But fortunately, there is much we can do to ease our minds and our field. Naturally, some practices vary according to the type of disease. I'd like to start by diving into a fungus that can infect an entire playing surface of turf in 48 hours; the most troublesome and dreaded disease on the list: gray leaf spot. To fully understand how to control it, I would like to tell a little about the disease itself before moving on to prevention and cure. I hope it answers most of your questions, but of course, feel free to contact me for more information at any time.
So what is gray leaf spot?
The gray leaf spot is caused by the fungus Pyricularia grisea, and is a very destructive disease of Lolium perenne (Ray Grass perenne). In addition, it can cause serious damage to the grass species Festuca (Festuca grasses), Cynodon (Bermuda grass), Eremochloa (centipedegrass grass) and Paspalum. The pathogen overwinter as spores and dormant mycelium on the lower leaves of plants and on the thatched roof. When temperatures rise and humidity is high, the fungus produces spores in necrotic tissue. From then on, the disease can spread rapidly. All things considered: a disease that is very difficult to control and that must be prevented, rather than cured.
When and where are you at risk for gray leaf spot?
When there is a combination of a continuous period of leaf wetness and high temperatures, the risk of infection is high. The temperature range in which gray leaf spot can appear is 15 to 39 ° C. At suboptimal temperatures (15-22 ° C or 32-39 ° C), a period of 21 to 36 hours is generally required. leaf moisture for infection. At optimal temperatures (22-32 ° C), the peak of infection can occur with as little as 9 hours of continuous leaf wetting.
Until recently, gray leaf spot was a grass disease found only in southern Europe and other places with hot climates. However, due to global warming and the disease's ability to adapt to new environments, we see that gray leaf spot is also becoming more prevalent in northern Europe. We also see that the disease develops earlier in the year than usual. Where gray leaf spot used to occur from June to August in southern countries, several cases of gray leaf spot in spring were already found in 2020 in the UK and Germany.
How can my lawn get infected?
Initially, fungal spores must be present in the grass in order to infect. The spores often come from previous infections, from water, from machines, and from people. Avoiding fungal spores on your lawn is next to impossible. The spore itself poses no real threat to your lawn at first; the immune system of the plant is the main factor. The immune system of a herbaceous plant can easily be compared to that of a human being, both highly developed. If a person is too cold or too hot, they automatically go into shock and become more susceptible to illness. The same applies to plants. Extremely dry, humid, hot or very cold conditions force the plant to enter "survival mode". As a result, the herb draws nutrients from its defense system to survive and thus becomes more vulnerable. This is also known as "weed stress" and is often part of the cause of the plant infection.
Due to the destructive nature of the disease, it is best to always try to prevent it. With the 11 tips below, you will have a good foundation for a healthy summer camp.
- Maintain a good balance between light, water, temperature, CO2 and nutrition to strengthen the immune system.
- Limit drought - I recommend watering your lawn liberally in the middle of the day rather than several short watering sessions (read why below).
- Limit extended periods of leaf wetness - Watering in the evenings and mornings can spread leaf moisture, which can become lawn stress when temperatures are high. Using the lawn fan on your TC50 / TF50 will dry out the plant and reduce the wet period of the leaves after watering or at times when humidity is relatively high.
- Limit nitrogen applications.
- Limit soil compaction with aeration.
- Reduce the cutting height.
- Reduce the temperature with TC50: With the cooling mechanism of the TC50, the temperature can be lowered approximately 6 ° C. The SGL portal provides calculated cooling tips based on meteorological data, to use the cooling mechanism of the TC50 of the most efficient way possible.
- UV-C light treatment: Preventive UV-C light treatment will reduce the incidence of disease. When biological organisms are exposed to UVC light in the range of 200 nm to 300 nm, the light penetrates through the cell wall and breaks the DNA molecules. The altered DNA cannot be replicated and therefore the fungus dies before it causes any damage to your lawn.
- Track SGL Disease Forecast - Based on weather forecasts and data collected by our monitoring tools, we provide accurate 10-day disease forecasts. Based on this prognosis, the disease pressure for disease is determined so that you can make proactive decisions and act on time.
- Record pasture disease cases. In this way, you can identify pasture disease patterns and anticipate them.
- Renew to keep your lawn's thatch layer as thin as possible.
But what if, despite all your efforts, you think about recognizing the gray spot on the sheet?
First of all: make sure you identify the disease with certainty as soon as possible. Especially since the gray leaf spot can infect a large area of the lawn surface in 1-2 days. Here are the symptoms of gray leaf spot. I would also recommend that a lawn disease specialist review a sample if you are not 100% sure. An incorrect diagnosis can lead to incorrect treatment, with the risk of worsening the situation.
What are the symptoms of gray leaf spot?
On cool-season lawns, symptoms first appear as small, water-soaked lesions, which quickly turn necrotic. Leaf spots can vary considerably in color, size, and shape, but are often:
- Gray to light brown
- Surrounded by purple to dark brown edges
In warm season lawns, small brown lesions on leaves and stems quickly enlarge into round or oblong spots. Larger spots can spread almost all over the leaf. In severe cases, the entire plantation dies, leaving behind resistant grass species or weeds. Leaf spots are tan to gray with purple to brown edges.
In both cool seasons and warm season lawns, the tips of wilted leaves often have a conspicuous twisted or hook-shaped shape and the thick masses of greyish spores can give the leaves a felt appearance. Lesions are also found on leaf sheaths, spikes, and stems. Under a microscope, spores on gray leaf spots are easily recognized, as they have a distinctive pyriform shape and a glassy appearance.
The most effective control method is the use of UVC180. If it turns out that your lawn is infected with the gray leaf spot, curative treatment with UVC180 will help reduce the spread of the disease. As mentioned above, UV-C light has the ability to alter the DNA of fungal spores, such as the gray leaf spot, preventing the fungus from reproducing. Because grass cells are much more resistant to UV-C light than fungal cells, the amount of UV-C light radiated by UVC180 is high enough to kill fungi and fight more breakouts. while the herb plant is not affected. Another option is to slightly reduce the cutting height in the areas where you see the first signs of gray spot on the blade.
Dra. Irene Vroegop
Irene is an Agronomist and Lawn Disease Expert at SGL. Her bachelor's degree in biology with a specialization in Environmental Biology and her Ph.D. in Plant-Microbe Interactions form a deep foundation for her research and advisory role within SGL's department of agronomy.