Increasingly organic pesticides are also being sought as an alternative.
Some organic pesticides contain live spores of the fungus Trichoderma, which have the ability to suppress other pathogens.
Researchers at the University of Göttingen have now discovered that one Trichoderma species can cause severe rot in cobs of maize.
The massive outbreak of a previously unknown species of Trichoderma on corn cobs in Europe was first detected in Southern Germany in 2018.
In affected plants, grey-green spore layers formed on the grains of corn and between the leaves that form the husks of the cobs.
18 separate Trichoderma strains mainly from maize cobs in Southern Germany and France over two years.
By means of molecular genetic analyses, these spores could be assigned to the relatively new species Trichoderma afroharzianum.
“The species used in organic plant protection products is a close relative, namely Trichoderma harzianum. Strains of this species were not as aggressive in the study, but in the inoculation experiments they also led to a slight infestation on the cob,” says Pfordt.
“Although the investigations carried out so far show that the Trichoderma strains used in organic plant protection products differ from the aggressive forms now found, it is also clear that the risks from the use of living microorganisms in plant protection must be thoroughly investigated,” adds Professor Andreas von Tiedemann, head of the Department of Plant Pathology and Protection at the University of Göttingen.
In vegetable growing, “Trichoderma agents” can be used, for example to control diseases such as Botrytis or Fusarium and to reduce rotting pathogens on the crop products.
Various organic products containing Trichoderma are available on the market.
Trichoderma species belong to the ascomycetes and are found worldwide in the soil, on plant roots, in decaying plant remains and on wood.