There are many different fungi and diseases that grass and weeds can get. Some are easy to control, while others aren’t. Let’s go through the main ones in Australia, so you know what you are looking at when you come across it.
Fungi
There are about 144,000 known species of fungi worldwide, which includes yeasts, rusts, smuts, mildews, molds and mushrooms. They can live in nearly every habitat, but most live on land mainly in soil on dead plants.
Fungi are neither plants or animals, they are organisms that have their own Kingdom. Fungi doesn’t eat like plants through photosynthesis, or animals through intestinal digestion, they live inside their food and secrete enzymes to dissolve nutrients which they absorb.
Rust
Rusts make grass have spots of red and yellow, just like the plant is rusting. It is actually an orange coloured spore that first appears on the underside of leaves.
Rusts are common on ryegrass, but affects many other species of grass. It occurs through the wetter months, and prefers lower, wetter leaves because it increases infection.
Rusts weaken plants, making it susceptible to other diseases.
Pythium Blight
Pythium Blight first appears as small, irregularly shaped spots with a dark outline and a lighter centre. Spots get larger over time, and usually join together. Diseased patches fade to a light-brown or a grey colour.
High humidity causes the blight to sprout spiderweb-like mold which means the fungus is growing rapidly.
Pythium Blight loves warm, wet weather where the temperatures are between 25-30°C. The disease develops when nitrogen levels are high, and that is when air temperature reaches 30°C. Under low nitrogen levels, the blight will develop slower.
Pythium Blight does not like fertilised ground, especially regularly fertilised.
Black or White Helminthosporium (Black or White Helmo)
This is a common black or white spot disease which is caused by Drechslera, Curvulari, Bipolaris and Exserohilum species of fungi. An attack can occur at any temperature between 3 and 30°C, with optimum temperatures between 15-30°C and loves high humidity.
Powdery Mildew
Makes the grass look like it is covered with white powder. This powder is Mycelium threads being caused by fungus. There are usually light spots on the blades of grass, but these go unnoticed until the mildew appears.
Brown Patch
This is a fungal disease that loves warm, wet conditions. It produces different sized brown patches on a lawn. Leaf blades have thin brown edges and yellow spots and lesions.
Bipolaris
Affects the whole plant, from roots to crown. It leaves brown to grey lesions, and death in patches along the leaf.
Grey Leaf Spot
A pathogen that causes grey lesions with a dark brown ring. It kills the leaf around the outer ring. Usually found in ryegrass and buffalo.
Red Thread
Infected grass has small circles and patches of threadlike pink structures called sclerotia.
Brown Spot
Infected grass has small dark circles caused by insects digging into the leaf matter.
Leaf Miners
Tiny insects scar the leaves leaving white curves paths and round spots with brown centres.
