When the mycelium of fungi spreads in the soil, forming an underground network, it often manifests as distinct circular patterns on the lawn surface. These circular patterns, commonly known as “fairy rings,” are a fascinating yet concerning phenomenon for lawn enthusiasts. There are three typical types of fairy rings:
Three Types of Typical Fairy Rings
- Brown Patch Rings: Characterized by one or more clearly visible rings of dead grass, ranging in color from straw to brown. The width of these rings can vary from a few centimeters to several dozen centimeters. The grass within and outside the rings remains relatively healthy and green.
- Dark Green Rings: These rings feature an unusually dark green color and an exceptionally lush growth of grass, standing out vividly against the surrounding lawn.
- Mushroom Rings: At the edges of dark green or brown patch rings, or sometimes even on seemingly normal lawns, clusters of mushrooms (fruiting bodies) emerge in a circular formation after rain. The appearance of mushroom rings is a telltale sign of fairy ring fungi activity. While mushrooms themselves are harmless to the grass, their presence indicates an active disease threat.
Manage These Diseases
Tackling fairy ring diseases requires patience and a comprehensive approach aimed at breaking the hydrophobic layer and inhibiting fungal activity. Common treatment methods include aeration/puncturing, deep watering, topdressing with sand or soil, and removing mushrooms (a temporary solution). Additionally, proper fertilization, moderate mowing, and improving air circulation and sunlight exposure are crucial. Using natural microbial agents like Trichoderma harzianum and Bacillus velezensis is a safe and effective alternative.
Summer, with its high temperatures and humidity, serves as a breeding ground not only for fairy ring diseases but also for various other lawn ailments. Although these diseases don’t form circular patterns, their destructive power is equally alarming. Environmental factors, including weather conditions, soil quality, and lawn maintenance practices, play a significant role. Among these, temperature, moisture (humidity, rainfall, rainy days, fog, and dew), and sunlight have the most profound impact, affecting both pathogen reproduction, spread, and invasion, as well as the host plants’ disease resistance.
Common Summer Lawn Diseases
Pythium Blight – The “Lightning Killer”
- Characteristics: This disease spreads at an astonishing speed, capable of causing large areas of grass to wither overnight.
- Identification: In the early stages, look for small, dark green, oily patches that feel greasy to the touch. In the morning, white, cottony mycelium is visible, which turns gray as the humidity drops and gradually disappears. The patches quickly expand into large, irregular areas of dead grass, with slimy, collapsed blades and rotting roots.
- Favorable Conditions: Sustained high temperatures and humidity, especially high nighttime temperatures, poor drainage, and excessive nitrogen fertilization.
Brown Spot – The “Smoke Ring Curse”
- Characteristics: It is the most common and destructive summer lawn disease.
- Identification: Circular or irregular yellowish-brown patches are characteristic. In the morning when humidity is high, a dark brown to purplish-brown “smoke ring” (wilted grass) often appears at the edge of the patches. When widespread, the lawn shows various-sized patches of dead grass with green centers and yellow borders, resembling a “frog-eye” pattern.
- Favorable Conditions: High temperatures and humidity (with leaves remaining wet for over 10 hours), high nighttime temperatures, and excessive nitrogen use.
Curvularia Leaf Spot – The “Deceiver After Drought”
- Characteristics: This disease typically erupts after periods of high temperature and drought followed by rain, and its symptoms can be easily confused with other diseases.
- Identification: Look for irregular, slowly expanding chlorotic or yellowish-brown patches. The crowns and roots of infected plants often exhibit reddish-brown to dark brown dry rot, distinguishing it from the wet rot of Pythium blight.
- Favorable Conditions: Rain or irrigation after high temperature and drought, poor and compacted soil, root damage, and insufficient nitrogen.
Keys to Summer Lawn Disease Prevention
When it comes to these summer lawn diseases, prevention is always better than cure. Here are some essential tips:
- Watering Wisely: Water deeply in the early morning, allowing the leaves to dry before nightfall. Avoid watering in the evening or at night. Follow the “see – dry – see – wet” principle and prevent waterlogging.
- Mowing Properly: Adhere to the “one – third rule” (never remove more than one – third of the grass height at a time). Consider raising the mowing height slightly in summer. Keep mower blades sharp and remove clippings promptly during an outbreak.
- Balanced Fertilization: Exercise caution with high – nitrogen fertilizers in summer, as they can encourage disease. Instead, increase potassium fertilization to enhance the grass’s stress resistance. Base fertilization on soil test results.
- Improving Air and Light: Prune lower tree branches to enhance air circulation and sunlight penetration, reducing humidity.
- Aeration and Dethatching: Regularly aerate the lawn to improve drainage and root respiration, and break up soil compaction. This is crucial for preventing and alleviating diseases like fairy rings and brown spot.
- Ensuring Drainage: Make sure the lawn has proper drainage to avoid water accumulation in low – lying areas.
- Selecting Resistant Grass Varieties: When establishing a new lawn or overseeding, choose grass varieties with strong resistance to local prevalent diseases.
- Early Detection and Intervention: Regularly inspect the lawn. Upon discovering small, abnormal patches, diagnose accurately and take targeted measures promptly.