Soil fauna reduce pathogenic fungi and their toxins


Wheat with fusarium headblight (© JKI/Rodemann)

An important step for soil protection is the conversion from conventional to ploughless conservation tillage. Crop residues are no longer incorporated into the topsoil but remain on the soil surface. Such a mulching layer protects the soil against erosion, mitigates the variation of moisture and temperature conditions and promotes soil biodiversity. However, a promotion of soil biodiversity and its activity is not only positive because pest organisms also benefit from straw amendment on the soil surface. A drawback of conservation tillage is the problem of an increasing infection risk with pests like soil-borne phytopathogenic fungi. Such fungi growing on crop residues endanger plant health in the subsequent crop, for instance Fusarium head blight is one of the most important fungal diseases in small grain cereals.

Farmers suffer from quantitative losses of crop yield and a decline in the quality of crop products. Worldwide, Fusarium species are one of the most important phytopathogenic fungi since they are widespread and produce mycotoxins. In the interest of ensuring public health protection, the European Commission has set maximum levels for certain mycotoxins in plant raw material and foodstuffs. In case a threshold is exceeded, crop yield is excluded from commercial use. The trichothecene mycotoxin deoxynivalenol is one of the most abundant mycotoxins in cereals. Good agricultural practice serves to prevent against phytopathogenic fungi by avoiding close crop rotations, by cultivating less susceptible cultivars, and by sustainable application of fungicides. These agricultural measures seem only to be partially successful. For that reason, scientists of the Thünen-Institute and the JKI conduct lab- and field-based experiments. They want to explore the extent to which common soil animals like earthworms, collembolans and fungi feeding nematodes may naturally repress the development of Fusarium species and reduce contamination by their toxins. These ecosystem services are at the focus of their joint research. In the context of soil health and soil protection, knowledge of the potential of antagonistic soil fauna groups and of their promotion by sustainable management measures is economically and ecologically important. Such knowledge enables researchers to find processes which assure safe agricultural production.