Fungi Trichoderma harzianum in winter

Trichoderma harzianum is rhizosphere competent. This means that the beneficial fungus can colonize the roots of a tree while they are still developing. The rhizosphere is the space in the soil directly influenced by a living root. From a soil ecological point of view, it is of particular interest because soil, plants and living organisms – especially microorganisms – interact intensively with each other here.

Illustration: Harman et al. 2004

Colonies of Trichoderma harzianum grow relatively fast. At ideal temperatures of 20-25 degrees for the beneficial fungus, it can grow 4-10 centimetres within a few days. It prefers the upper 20-30 cm in the soil and the littler layer, where it finds enough food in the form of dead plant parts, secretions of roots and possible fungal pathogens as well as light.

Rapid growth of Trichoderma harzianum

Without light, the whitish fungal filaments (hpyha) grow without the formation of spores. When exposed to light, the fungal strain produces spores. The hypha are separated and transparent and together form the mycelium. At the conidiophores – the spore carriers – there are bottle-shaped phialids in which the green-pigmented spores (also called conidia) are formed.

The cooler the temperature, the more inactive the beneficial insect becomes. Below 12 °C ground temperature Trichoderma harzianum falls into a kind of hibernation. As soon as it gets warmer again, the activity and growth increases in combination with the available nutrients and the given humidity.