This is arguably one of the most common and damaging of the cool season diseases. Although an outbreak can occur at any time of the year, it is much more likely to occur during the cool and damp autumn and winter months in the UK.
Fusarium patch is more problematic on closely mown grass, such as golf & bowling greens. Although most types of grass species are susceptible to this disease, annual meadow grass (Poa annua) dominated turf is very susceptible to attack.
Identifying Fusarium Patch
The initial signs of disease infection are small water soaked orange – brown patches between 10 – 20mm in diameter. In favourable conditions the infected patches rapidly increase in size, commonly reaching up to 300mm in diameter.
As the severity of the infection increases the patches often join together, causing extensive damage the the turf. Often, on damp dewy mornings white cobweb like structures can be observed on the infected areas. These white structures are known as mycelium.
If the disease is not controlled then the whole plant may die, leaving unsightly scars in the turf that will not recover until spring time with the onset of growth.
Conditions that favour Fusarium Patch
- Cool and damp soil conditions, typically associated with the autumn and winter periods.
- Excess levels of nitrogen caused by applying high nitrogen feed during the late summer early autumn period will promote lush growth and increase the risk of a disease outbreak.
- All shaded and sheltered areas of turf that lack air movement and sunlight will be more susceptible to attack.
- Areas of turf that contain a high percentage of Annual meadow grass (Poa Annua) will be very susceptible to Fusarium Patch.
- Surface alkalinity (high pH) caused by applying materials such as lime will increase the risk of Fusarium.
- A wet rootzone caused by poor drainage or an excessive thatch layer will only encourage dampness in the base of the sward, thus increasing an outbreak.
Prevention and control of Fusarium Patch
- Avoid applying applications of fertiliser with high nitrogen inputs late in the growing season. Apply a fertiliser with high levels of phosphate and potash. These nutrients (especially potash) are essential for good winter turf hardness and will help prevent disease.
- Regular mechanical operations such as scarifying and aeration will help prevent and control the build up of thatch, relieve soil compaction and encourage a dry surface.
- Removing early morning dew to help promote a dry surface will help reduce the risk of a disease outbreak. Removing or pruning back any tree branches or vegetation will encourage airflow and increase available sunlight to help keep the turf drier.
- If possible reduce the percentage of annual meadow grass in the sward by encouraging grass species such as bent and fescue with good turf management techniques.
- Fungicides are available to turf professionals such as golf greenkeepers for the control of Fusarium patch. However the amateur gardener does not have the luxury of these fungicides, their choice is very limited. Luckily disease problems on a typical lawn are uncommon and rarely warrant the use of a turf fungicide.