Abstract:In order to understand the antifungal and nematicidal activities of five volatile compounds as soil fumigants, trans-2-hexen-1-al, citronellal, linalool, 1-octen-3-ol, and 1-penten-3-ol, were tested for their activities against seven soil-borne pathogenic fungi and two nematodes, Meloidogyne incognita and Heterodera avenae in sealed dishes. Trans-2-hexen-1-al and citronellal showed relatively higher biological activities than linalool, 1-octen-3-ol, and 1-penten-3-ol. Trans-2-hexen-1-al could completely inhibit mycelium growth of pathogens at the concentration of 21.0 μL/L. Both of trans-2-hexen-1-al and citronellal with 10.5 μL/L could significantly inhibit the spores formation of Aspergillus niger and the pigment formation of Verticillium dahlliae, and at 42.0 μL/L they could completely inhibit the sclerotium germination of Sclerotina sclerotiorum. Trans-2-hexen-1-al (2.62 μL/L) induced a mortality of 100% to the 2nd instar larvae of both M.incognita and H.avenae when applied over 24 h, while citronellal (2.62 μL/L) induced a mortality of 95.4% and 89.5%, in contrast to the 2.5% and 3.0% mortality respectively in the control. The results showed that both of trans-2-hexen-1-al and citronellal possess strong fumigant antifungal and nematocide activities.