Wednesday, November 7, 2007
285-1

Use of Two Adsorption Models to Describe the Fate of Entomopathogenic Nematodes in Soils.

Samuel Dennis1, Robert Harrison1, Teferi Tsegaye2, and Sunnie Aburime3. (1) IAgER, Tennessee State University, 3500 John A. Merritt Blvd, Nashville, TN 37209, (2) Alabama A&M University, P.O. Box 1208, Department of Plant & Soil Science, Normal, AL 35762, (3) Research Center for Science & Technology, Clark Atlanta University, 223 J. P. Brawley Dr, Atlanta, GA 30314

Entomopathogenic Nematodes (ENs) are potential bio-control agents for soil-borne insects like the white grubs of the scarab beetles. Knowledge of their fate in soils is important for their release into the soil environment. The study seeks to examine the fate of Steinernema carpocapsae TN 18 strain, an entomopathogenic nematode, in nursery soil at the column scale. Two field soils were used to pack the columns. The soils had history of nursery crop production for at least ten years. A Darcian flux (0.8 cm hr-1) was used to facilitate movement (leaching) of the nematodes in disturbed soil columns. Bromide concentration of 0.8 M, non-toxic to the nematodes was added to the soil surface as a conservative tracer. Leachate samples were assayed for nematodes and bromide concentrations. Bromide and nematode breakthrough curves, as well as two adsorption models, were used to provide evidence of entomopathogenic nematodes' fate and transport processes in the soils. The amount of ENs sorbed to soils was tested with two adsorption isotherms (Freundlich and Langmuir). A good fit of the data was obtained with the Freundlich isotherm while the Langmuir isotherm exhibited a non-linear fit. Relatively, the bromide and nematodes' BTCs indicate that the ENs movement was retarded in both field soils, suggesting that sorption might be a key factor in determining nematodes transport through soil.