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Soil-incorporated plant materials have been associated with reduction in soilborne pathogens and diseases. Mechanisms of the biocidal actions are complex and not well understood. A glasshouse experiment, a non replicated field demonstration, and a field experiment were conducted to determine volatile compounds after incorporation of various plant species and their effect on pest control. Cabbage (Brassica oleracea), canola (Brassica rapa), kale (Brassica oleracea var. acephala), lettuce (Lactuca sativa var. valmaine), two mustard varieties -Caliente (Brassica juncea) and Green wave (Brassica juncea), two radish varieties -Oil seed (Raphanus sativus var. oleiformis) and Cherriette (Raphanus sativus), common rye (Secale cereale), and sorghum Sudan grass (Sorghum bicolor var. sudanese) were used in the glasshouse experiment. Caliente 199 mustard (Brassica hirta) was planted in the field demonstration and white mustard (Sinapis alba) was used in the field experiment. Fresh plant materials were chopped manually in the glasshouse experiment and mechanically in the field studies at the flowering stage before incorporation in natural field soils. In the glasshouse experiment, the equivalent biomass dry weight ranged from a minimum of 573 gm −2 for L. sativa var. valmaine to a maximum of 1851 gm −2 for S. bicolor var. sudanese. The average biomass was 792 gm −2 for B. hirta and 804 gm −2 for S. alba in the two field studies, respectively. The glasshouse experiment used a loamy sand field soil inoculated with a natural fine sandy loam soil that was known to contain high populations of Verticillium dahliae. Soils at both field sites belonged to the sandy loam series, and efforts were made to maintain sufficient soil moisture for plant growth. Although the interest was to determine all volatile compounds in general, only methyl sulfide and dimethyl disulfide were identified and subsequently quantified. Depending on plant species and time of sampling (one to seven days after soil incorporation), 2.7 to 346.4μg g −1 plant dry weight for methyl sulfide and 0 to 283.2μg g −1 plant dry weight for dimethyl disulfide were found in the glasshouse experiment. In general, high concentrations of dimethyl disulfide and methyl sulfide appeared to have reduced V. dahliae colony counts in bioassay potato stem saps in the glasshouse experiment. However, the correlation was weak (R 2 =0.31), but a relatively stronger correlation

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