Trichoderma tomentosum

The most distinct symptom is the formation of a white, felt-like fungal growth on the surface of seeds or the base of stems. Affected tissues quickly lose their structural integrity and begin to rot.

Seedling blight is a common manifestation, where seeds fail to emerge or collapse shortly after germination. This results in poor stand establishment and noticeable gaps in crop rows.

In older plants, root symptoms include browning and necrosis of the root cortex. Under high humidity, a greenish tinge often appears on the fungal mat, indicating active spore production.

Wilting of the foliage is a secondary effect of root damage. As the vascular system of the root becomes compromised, the plant cannot absorb sufficient water, leading to a loss of turgor pressure.

In greenhouse environments, the infection may appear as patches of collapsed seedlings, with the fungus spreading radially from the initial point of infection through the growing medium.

The causative agent of this disease is the fungus Trichoderma tomentosum. Although many species in the Trichoderma genus are known as beneficial biocontrol agents, this specific species can exhibit parasitic behavior under certain environmental conditions.

This fungus is essentially a soil-dwelling saprotroph that can opportunistically attack plants. It thrives in the upper soil layers, utilizing organic matter before transitioning to plant tissues when the host is stressed.

The fungus is characterized by the production of a dense, felt-like mycelium, which is the primary source of its specific name. This mycelial mass allows the fungus to rapidly colonize the rhizosphere and compete with root microflora.

The pathogen reproduces via conidia, which are highly resilient structures. These spores can persist in the soil for extended periods, remaining viable despite fluctuating weather conditions and low nutrient availability.

The aggressive colonization ability of this species allows it to outcompete other microorganisms in the immediate vicinity of plant roots, often secreting metabolites that are toxic to young, developing plant tissues.

High soil moisture is the primary driver for Trichoderma tomentosum outbreaks. Soil saturation levels above 75-80% significantly increase the risk of rapid colonization.

The pathogen is most active within the temperature range of +18°C to +25°C. These temperatures are often found in greenhouse settings and during late spring in field conditions, favoring the rapid spread of the fungus.

Soil pH levels on the acidic side (pH 5.0–6.0) tend to facilitate the pathogen’s ability to infect plant roots, while neutral or slightly alkaline soils often suppress its activity.

Poor soil aeration and high organic matter content from un-decomposed residues provide an ideal environment for the fungus to establish its population before targeting live plant hosts.

Lack of adequate ventilation in greenhouses and high plant density increase the relative humidity around the plant base, creating the perfect microclimate for the fungus to develop its characteristic felt-like mycelium.

The primary damage caused by this fungus is the significant reduction in crop stand, leading to the necessity of replanting and increased production costs.

Root system injury hinders the plant's nutrient and water uptake, resulting in stunted growth and a considerable decrease in the overall marketable yield of the affected crop.

The fungus facilitates secondary infections. By damaging the integrity of the roots and stems, it creates entry points for other opportunistic pathogens, potentially leading to a synergistic effect of tissue destruction.

The quality of harvested produce is often compromised if the fungus attacks the basal parts of fruits or root vegetables, making them unsuitable for storage and sensitive to post-harvest decay.

Persistent soil contamination by the pathogen limits the choice of future crops, as high inoculum levels can make the ground unsuitable for susceptible species for several seasons.

Effective crop rotation is essential to break the pathogen's life cycle. Avoid planting highly susceptible crops in the same plot more frequently than every three to four years.

Improved soil drainage and irrigation management are critical. Preventing water stagnation is one of the most effective ways to discourage the fungus from colonizing the root zone.

• Use high-quality, fungicide-treated seeds to ensure early protection.
• Amend the soil with lime to raise the pH if the soil is overly acidic.
• Apply systematic fungicides at the onset of disease symptoms to limit the spread.
• Practice thorough sanitation by removing and destroying infected plant debris.

Steam sterilization of soil or the use of approved chemical disinfectants for pots and tools in greenhouses can help keep the pathogen population below the economic threshold.

Promoting a healthy soil microbiome by adding compost and avoiding excessive chemical applications can foster biological competition, making it harder for the pathogen to establish itself.