Can soilborne diseases be combated with biorationals?

Controlling soilborne diseases, caused by plant pathogens such as Fusarium and Pythium, is becoming increasingly difficult. Partly due to the reduced availability of chemical crop protection products. Alternative strategies are needed to protect the plants from soilborne pathogens. That is why the Business Unit Greenhouse Horticulture and Flower Bulbs of Wageningen University & Research (WUR) is investigating whether biorationals (plant protection products of natural origin) can be used effectively in greenhouse cultivation against soilborn plant pathogens.

Fungi (such as Fusarium and Verticillium) and oomycetes (such as Pythium and Phytophthora) can infect a crop through the roots, causing damage. WUR is investigating whether these infections can be prevented with biorational agents, such as biopesticides. Such agents are increasingly available on the market for use in crops, but their potential remains underused. The question is how these products can protect the plants against soilborne pathogens during the entire lenght of a cultivation cycle.

The research is conducted in two model crops: lisianthus and cucumber. Cultivation of lisianthus is soil-based with a relatively long propagation period (around 12 weeks) and relatively short cultivation in the greenhouse (7-8 weeks), while cucumber cultivation is much longer (up to 4-5 months) and takes place in inert growing medium (stonewool or perlie).

The first results show that the micro-organisms (which are present in the soil or other growing medium and in rhizosphere) are important in combating the infections of pathogens such as Fusarium. Application of some biorational products can influence the composition of the natural, microbial community in the soil or the growing medium in such a way that the pathogens present have less chance of infecting the plants. However, optimization of the applications is needed, so that maximum protection of the plants can be achieved during the entire cultivation cycle.