Fungal disease control

Control using fungal and bacterial pathogens

Parasitic fungi

Assorted biological agents are available to control fungal diseases. The fungus Ampelomyces quisqualis, which exclusively parasitises mildews, is used in viniculture and greenhouses against mildew on cucumbers. The genera Trichoderma and Gliocladium, which are the basis of assorted plant protection preparations, also belong to the group of parasitic fungi that live on other fungi.

Fungi as space and nutrient competitors

Other biological agents successfully colonise hollows on leaves and fruits of the plants, thereby preventing the growth of harmful fungi. Such agents include yeasts (Aureobasidium pullulans). The fungi create an acidic environment on the treated parts of the plant, and are therefore also used against the bacterial causes of fire blight, which cannot grow in the acidic environment.

The fungus Aureobasidium pullulans has been used since 2005 as an alternative to the antibiotic Streptomycin. In forests, the fungus Phlebiopsis gigantea has been used since the end of the 1980s to prevent red rot fungus from colonising spruces and pines.

Bacteria against fungi

Last but not least, bacteria are also available which serve as fungal control agents. The use of Bacillus species is very widespread. The Bacillus subtilis preparation Serenade(tm) is used especially to protect those parts of the plant that are above ground whereby various substances made from the bacteria suppress fungal growth on the plants. The roots and soil are also treated using bacteria to control fungal diseases. In addition to Bacillus species, Streptomyces and Pseudomonas species are also used; the latter has been used widely in Sweden since 2000 to treat barley and wheat, with increasing use being made in other European countries.

Strengthening the plants defence mechanisms

Plants often have suitable defence mechanisms to survive fungal infections. Various microorganisms are able to trigger this defence mechanism in the plants, although the effect of this induced resistance in plants varies. Often, treating the seed or propagation material is enough to induce resistance. In the case of the bacterium Serratia plymuthica, the effect of the bacterial signalling substance on plant resistance has been proven. Bacillus species or non-pathogenic strains of harmful fungi can also trigger such forms of resistance.

Plant-based ingredients are also used to control fungal diseases. One example is extract of giant knotweed (Reynoutria sachalensis), which induces plants' resistance reaction against mildew diseases and botrytis (grey mould).