Evaluation of continuous application technology for delivery of the biocontrol agent Pseudomonas putida 06909-rif/nal

We evaluated a commercial field fermenter as a means of culturing and deliv ering a bacterial biocontrol agent, Pseudomonas putida 06909-rif/nal, throu gh irrigation water. There was no evidence of contamination in 12-hour cult ures produced by the fermenter. It produced 120 liters of inoculum at 5 x 1 0(8) CFU/ml after 12-hour fermentations, allowing two applications per day. Dilutions up to 1:100,000 of inoculum of P. putida 06909-rif/nal produced by the fermenter allowed the biocontrol agent to effectively colonize soil in greenhouse trials. Bacteria produced in 19-hour fermentations colonized soil better than bacteria produced in 12-hour fermentations. Ten repetitive applications of P. putida 06909-rif/nal yielded soil population levels sim ilar to those from a single application at 10-fold greater concentrations. Repetitive applications of lower concentrations may be a cost-effective met hod for delivering bacterial biocontrol agents to large acreages. This work suggests that the commercial field fermenter would be a viable instrument for delivering bacterial biocontrol agents for commercial-scale field appli cations.