Paspalum anthracnose

The early symptoms of Paspalum anthracnose appear as irregular, chlorotic patches of turf. The leaves initially turn a yellowish-brown color, which gradually deepens into a dark, necrotic shade as the disease progresses.

A hallmark sign of the infection is the presence of acervuli, which appear as tiny black dots on leaf blades and sheaths. Under magnification, these acervuli display characteristic black setae (stiff hairs), which confirm the identity of the pathogen.

Infected areas often manifest as thin, ragged patches of turf. The roots of the affected plants become discolored and soft due to the basal rot, which is common in advanced stages of the disease.

The turf may lose its vibrant green color and appear stunted. In severe cases, large patches of the lawn can die off, leaving bare spots that are prone to colonization by invasive weeds.

During humid mornings, a faint fungal growth may be visible on the surface of the dying tissue. This indicator is often followed by the rapid browning of the foliage, leading to visible lawn decline.

The disease is caused by the fungal pathogen Colletotrichum paspali, an imperfect fungus that primarily infects Paspalum species. It is a major concern for golf course managers and turf specialists who maintain highly specialized grass surfaces.

The pathogen survives within infected plant debris and soil during dormant periods. It produces fruiting structures known as acervuli, which house numerous conidia, serving as the primary inoculum for new infections during the growing season.

Transmission occurs through splashing water, wind movement, and mechanical equipment such as lawn mowers. The fungus infects the host through stomata or directly through the cuticle, especially where plant tissue has been damaged.

Inside the plant, the fungus develops an extensive mycelial network, secreting enzymes that degrade cell walls. This internal colonization leads to the disruption of water and nutrient transport systems, causing the plant to wither.

The high specificity of Colletotrichum paspali allows it to thrive in dense, monoculture turf stands. By rapidly depleting the plant's resources, the fungus compromises the entire integrity of the turfgrass system.

Environmental conditions are critical for disease outbreaks. The fungus flourishes in periods of high humidity and warm temperatures, typically ranging from 25°C to 30°C, which are common during the summer months.

Plant stress is a primary driver of the infection. Turfgrass that is subjected to frequent low mowing, improper fertilization, or soil compaction is significantly more susceptible to Colletotrichum paspali.

Excessive moisture on the leaf surface, whether from prolonged dew or over-irrigation, provides the necessary environment for conidia to germinate and penetrate the host tissue effectively.

Poor soil drainage and low oxygen levels in the root zone weaken the grass's immune response. This physiological stress makes it easier for the fungus to establish a strong foothold within the turf stand.

Lack of proper airflow around the turf canopy prevents the foliage from drying out quickly, which is a major factor in the rapid spread of the disease across golf greens and lawns.

Paspalum anthracnose can inflict severe damage on sports surfaces, making them unsuitable for play. The speed at which it destroys the turf is its most destructive characteristic, often causing widespread decline in just days.

Financial losses can be substantial, as management requires intensive fungicide programs and often the total renovation of affected turf areas, including reseeding or sod replacement.

The disease weakens the host plant, leaving it vulnerable to secondary infections from other pathogens. This cumulative damage can significantly shorten the lifespan of a turfgrass area if left untreated.

Root rot reduces the plant's ability to cope with environmental stresses like drought or heatwaves. This makes the lawn extremely difficult to maintain during the peak of the growing season.

Beyond the functional damage, the aesthetic impact is severe. The presence of brown, sparse patches renders a lawn visually unappealing, which is unacceptable in premium landscape management and commercial sports venues.

An effective control program starts with proper cultural management. This includes increasing the mowing height, improving soil aeration, and ensuring balanced nitrogen fertilization to support plant vigor.

To reduce moisture duration on leaves, irrigation should be scheduled during the early morning hours, allowing the grass to dry out quickly during the day, which discourages fungal growth.

Sanitation is essential; mowing equipment must be thoroughly cleaned and disinfected after contact with infested areas to prevent the spread of fungal spores across the entire site.

Chemical control involves the application of systemic fungicides, such as strobilurins or DMI inhibitors. It is critical to rotate between different chemical classes to prevent the fungus from developing resistance.

Regular monitoring of turf health and soil conditions helps in early detection. Implementing these preventative measures significantly reduces the need for heavy chemical intervention later in the season.