The efficacy of solarization to reduce soilborne inoculum has been tested in many crop systems. In cotton, the viability of FOV chlamydospores was used to measure the success of three field soil treatments. Nylon bags filled with 2 × 103 propagules, mostly chlamydospores, in field soil were buried at a depth of 25 cm in two fields in Davis, California (Ben-Yephet et al., 1987). Treatments were uncovered soil, soil covered with one layer of polyethylene (25 μm thick) film and soil covered with a double layer of polyethylene film separated by 6.3 cm diameter polymerized vinyl chloride pipe. Soil was watered to 40 cm deep at 70% of field capacity and the solarization lasted for 31 days (Ben-Yephet et al., 1987). The double polyethylene film treatment reduced FOV chlamydospore viability by 97.5%, highlighting the insulating layer between the polyethylene film as key to heat retention and the efficacy of field solarization.