The root-knot nematode (RKN) (Meloidogyne incognita) is one of the most important pathogens on
greenhouse-cultivated cucumber in northern China, and chemical nematicides are neither ecofriendly
nor cost-effective. Thus, more benign and acceptable biological control measures for this destructive
pathogen are required. Thein vitro ovicidal and larvicidal activities ofSyncephalastrum racemosum,
Paecilomyces lilacinusandBacillus cereuswere tested on cucumber, and their combined effects against
M. incognitawere evaluated in pot and greenhouse experiments. The chemical nematicide fosthiazate
was evaluated for comparison. All the bioagents displayed nematicidal potentialviatheir ovicidal and larvicidal action, except theB. cereusbioagent at a concentration of 2%. The highest ovicidal activity was
recorded for the combination ofS. racemosumandP. lilacinusat a concentration of 50%, which resulted
in an approximately 70% reduction in egg hatching compared to the control. The best larvicidal activity
was observed in theS. racemosumtreatment at a concentration of 50%, which caused a 96.7% mortality
rate. Under the pot conditions, compared to the untreated control, the application ofS. racemosumcombined withP. lilacinussignificantly stimulated the root length, shoot length and plant weight of cucumber
plants, and significantly fewer galls and nematodes were observed. Under the greenhouse conditions, the
combination ofS. racemosumandP. lilacinusnot only decreased the nematode severity but also increased
the cucumber yield compared to the untreated control. Among all the treatments, the combined application ofS. racemosumandP. lilacinuswas more effective at controllingM. incognitathan other treatments,
except for the fosthiazate treatment. The results indicate that the combined use ofS. racemosumandP.
lilacinusrepresents a new biocontrol strategy against parasitic nematodes in protected agricultural areas