Greenhouse growers are faced with a variety of plant pathogens and pests when cultivating crops in the soil. Some examples include: root knot nematodes, Pythium, Fusarium, Rhizoctonia and Verticillium. In organic vegetable cultivation in the Netherlands, root knot nematodes are one of the major problems.
The problems with root knot nematodes also increasing in other soil based cultivation systems, such as chrysanthemum or other ornamental crops production. The numbers of available and effective chemical control products against soilborne diseases and pests are limited.
In addition, the combination of different pathogens can be a problem in soil-based cultivation. The presence of root knot nematodes, for example, can increase the sensitivity to Verticillium or Fusarium.
Disease supressive soil
An alternative is a disease suppressive soil. Disease suppression in soil is a result of various factors and therefore requires a system approach. In addition, combining different measures can increase soil disease resilience through synergistic effect.
At Wageningen University & Research, BU Greenhouse Horticulture in Bleiswijk and Louis Bolk Institute in Bunnik, a research project is currently underway into possibility of increasing soil suppression against root knot nematode (Meloidogyne sp.), Pythium ultimum and Verticillium dahlia.
This can be achieved through the use of different management strategies such as increasing soil organic matter and biodiversity through compost addition or through intercropping, with plants that produce secondary metabilites, which adversly influence nematode population.
The effects of compost
Each commercial cultivation company has to deal with different soil type and infection rate of root knot nematodes. It is therefore important that proposed measures are broadly applicable to different soil types.
Research at Wageningen Plant Research, with tomato and chrysanthemum, shows that adding compost to the soil can result in a significant reduction of root knot nematode infestation. There is also clear synergistic effect of compost addition together with beneficial microorganisms. This effect was observable in soils of different origins (biota cultivation or conventional cultivation) and on different soil types.
This research is funded by Chrysanthem NL, growers of organic vegetables, Foundation Program Fund for Greenhouse Horticulture and Top Sector Agri & Food.