The potato cyst nematode, Globodera rostochiensis, is a quarantine organism. Environmentally benign control measures for this economically important pest are needed. Green manures, in particular plants from the Brassicaceae, suppress some plant-parasitic nematodes and have potential as control agents. This study examined if growing and incorporating cover crops from the Brassicaceae family influenced hatching of G. rostochiensis. The effect of root diffusates and plant extracts, as well as soil incorporation of plant material from three commonly used species of green manures, was studied in in vitro bioassays and pot tests. The results showed that brassica diffusates and plant extracts were not nematicidal. In addition, although they did not cause hatch by themselves, pretreatment with these solutions enhanced subsequent hatch in host root diffusates. The results are discussed in the context of the hatching response of G. rostochiensis and the likely influence on field usage of these green manures.