Technical Abstract: Several commercially available biopesticides and phosphonate-containing products were selected and tested for their efficacy in controlling Phytopthora capsici on bell pepper at various inoculum and fertility levels. The effects of concentration, application method and frequency of application on the efficacy of phosphonates were deteremined, and the efficacy and toxicity of selected commercially available phosphonate-containing products against Phytophthora root rot on bell pepper was tested. The efficacy of four commercially manufactured biopesticides was tested against increasing concentrations (50, 500, and 5,000 zoospores/plant) of Phytopthora capsici. In a second series of experiments, six biopesticides and an untreated control along with four fertilizer concentrations were tested to determine if there was an interaction between plant fertility and disease control wtih the biorational materials. From these experiments, it was determined that, while increased inoculum concentration had a significant impact on disease severity, there was no interaction with biopesticide treatment. Only the phosphonate-based material provided disease control. Fertility had no impact on disease control. Since the phosphonate material was the only product that provided consistent disease control, application method and frequency of application of this material was investigated. Drench applications significantly reduced disease levels in pepper, without causing any phytotoxic damage, while foliar applications did not control disease. Six different phosphate- or phosphonate-based materials were compared for their ability to control this disease when applied to foliage or as a drench. Only FNX-100 (BioPhos) and K-Phite provided control when applied as a drench treatment.