Cover crops for plant protection : Cover crops for control of root pathogenic Plasmodiophora brassicae and the root parasitic nematodes Pratylenchus penetransand Meloidogyne hapla

Sammanfattning: Root pathogens and parasites are an increasing problem in agricultural and horticultural production. The soil borne pathogen Plasmodiophora brassicae is one of the major pathogens in oilseed rape production and the plant parasitic nematodes (PPNs), Pratylenchus penetrans and Meloidogyne hapla infest important crops such as carrot, potato and strawberry. In common, both of the nematodes and Plasmodiophora brassicae strongly depend on host plants for reproduction, and are difficult to control. There is a need for clever integration of multi-tactic strategies to prevent their dissemination. In the present study, cover crops were examined in bioassays for their potential to decrease the population density of both nematodes and infection level of Plasmodiophora brassicae. The examined cover crops in the Plasmodiophora brassicae trial Lolium perenne and Lupinus angustifolius, revealed medium high disease severity indices (DSIs) on the indicator plant Brassica napus. However, no significant decrease was found in comparison to plant free soil (fallow). In the PPN trials, the cover crop species Avena strigosa and Lupinus angustifolius were investigated. Promising results were obtained for A. strigosa indicating high resistance to M. hapla and very efficient suppression of Pratylenchus penetrans in infested soil. Lupinus angustifolius was found to be susceptible to M. hapla and to be a poor host species for Pratylenchus penetrans. Potentially A. strigosa could be recommended in crop rotation where both nematode species are challenging the production of susceptible cultivars. Lupinus angustifolius should be avoided in crop rotation where M. hapla is present but may be used in crop rotation where Pratylenchus penetrans is present to prevent excessive multiplication. Further studies are needed to determine the potential of Lupinus angustifolius, as contradictory results have been reported from experiments with different varieties of the cover crop.