Detection of grass diseases VI. Anthracnose

Turfgrass anthracnose is a fungal disease widely recognised for its ability to cause significant damage to golf courses, sports fields and green landscapes. From its discovery in the early 1900s to the present day, turfgrass anthracnose has been the subject of intense research and development of management strategies to mitigate its impact.

Causative agent:

The causal agent of anthracnose of turfgrass is the fungus Colletotrichum cerealeformerly known as Colletotrichum graminicolaalthough in some regions, such as Korea, the fungus Microdochium bolleyi has also been associated with this disease. The fungus can survive over winter as mycelium or conidia associated with previously infected plant tissue. In addition, the fungus can survive as aggregates of pigmented hyphae called appressoria, which attach to plant surfaces and produce infection spikes that penetrate tissues and cause disease.

The LIFE CYCLE of the fungus involves the production of spores on acervuli of diseased plants, which can be transported to non-diseased plants via water, footwear and lawn equipment. Once the spores germinate, the emerging hyphae form appressoria that penetrate plant tissues and cause disease.

Symptoms:

The symptoms of grass anthracnose may vary depending on the species of turfgrass affected and the time of year when the disease occurs. In general, anthracnose can manifest itself as a leaf lesion or a basal rot of the lower stem. In the case of foliar lesionsin agrostis, reddish-brown spots appear, while in poa annua the symptoms include elongated and chlorotic spots containing black, spore-bearing structures. In some cases, older leaves may become completely watery.

On the other hand, the basal rot occurs when the leaf sheaths at the base of the internodes are colonised by the fungus, causing the infected tissue to turn brownish-black. dark brown to blackand the leaves turn orange to yellow in colour without lesions. In addition, the following may be observed clusters of infective mushrooms or infective stromata black spots in the plant tissue, which are spore-producing structures of the fungus.

Most susceptible species:

Grass anthracnose mainly affects grasses in temperate and cool climates. Poa annua and agrostis (Agrostis spp.) the species most susceptible to the disease, however, it can also affect other turfgrass species.

Conditions conducive to infection:

Turfgrass anthracnose tends to develop under conditions of stress to the turf, such as extreme temperatures, drought, excessive traffic, inadequate irrigation, poor fertilisation and wet soils.

• Optimum temperatures for the growth of the fungus causing anthracnose are between 21 - 28°CHowever, disease can occur when soil and air temperatures are significantly lower or higher than this range.
• The disease is associated with soil problemssuch as compaction, layering of different soil textures, use of inferior root zone mixtures and/or inadequate construction practices, which cause restricted drainage and poor root development.
• The wet soils are frequently associated with anthracnose outbreaks; therefore, the disease is more likely to occur after periods of excessive rainfall and high humidity.
• Any condition that slows the drying of turf and soil surfaces, including cloudy periods, shade, poor air circulation and poor drainagetends to exacerbate anthracnose.
• In addition, the nitrogen and potassium deficiency in turf may increase susceptibility to anthracnose.

Cultural control:

Cultural control of anthracnose of turfgrass focuses on reducing stress The disease tends to develop under stressful conditions for turfgrass. Some cultural practices that can help reduce the severity of anthracnose include soil aeration, reduction of organic matter, use of lightweight mowing equipment, increased fertilisation of nitrogen, potassium and sufficient irrigation to prevent drought stress.

In addition, it is important to carry out management practices that alleviate the poor drainage conditions, compaction and wet surfaces, such as aeration, redirection of traffic, reduction of irrigation and pruning or removal of trees.

Small amounts of nitrogen in summer, increased cutting heights and light roller passes to replace mowing are also highly recommended strategies.

Chemical control:

Chemical control of grass anthracnose involves the use of specific fungicides that are registered for the control of this disease. Several types of fungicides are effective for the preventive and curative control of anthracnose. These include contact fungicides such as chlorothalonilPenetrating fungicides, such as trifloxystrobinand systemic fungicides, such as propiconazole.

Resistance has been observed in some cases of Colletotrichum cereale to certain fungicides, such as thiophanate methyl and QoI fungicides (quinone outer quinone inhibitors/estrobilurins), such as azoxystrobin, trifloxystrobin and pyraclostrobin. Therefore, it is advisable to alternate the use of penetrant fungicides in different classes and to mix contact fungicides with penetrant fungicides in a control programme to delay the development of resistance.

Analysis and diagnosis of Anthracnose:

The most effective way to diagnose Anthracnose is always by testing for qPCR fast where we can identify dozens of diseases with a single sample.

Do you need to efficiently diagnose the incidence of Anthracnose or its potential affection? Contact Tiloom at info@tiloom.com and in less than 48 hours you will have the answer through a qPCR diagnostic analysis of the most common grass diseases.

Accurate knowledge of potential diseases affecting your lawn will enable you to act preventively and manage it in the most effective way. sustainable and efficient possible.

Bergstrom, G. C. and R. L. Nicholson. 1999. The biology of corn anthracnose. Plant Disease 83:596-608.

Chaky, J., K. Anderson, M. Moss, and L. Vaillancourt. 2001. Surface hydrophobicity and surface rigidity induce spore germination in Colletotrichum graminicola. Phytopathology 91:558-564.

Horvath, B. J. and J. M. Vargas Jr. 2004. Genetic variation among Colletotrichum graminicola isolates from four hosts using isozyme analysis. Plant Disease 88:402-406.

Vargas, J. M., Jr. and R. Detweiler. 1985. Anthracnose of Poa annua: the pathogenicity of Colletotrichum graminicola. International Turfgrass Society Research Journal 5:637-640.