EFFECTS OF SOIL SOLARIZATION AND FUMIGATION ON SURVIVAL OF SOILBORNE PATHOGENS OF TOMATO IN NORTHERN FLORIDA

The effects of soil solarization and fumigation, alone or combined, on survival of Fusarium oxysporum f. sp, radicis-lycopersici, F. o. lycopersici, Phytophthora nicotianae (= P. parasitical, and Pseudomonas solanacearum were examined in field plots in northern Florida. Soil solarization was performed over a 32- to 49-day period using a photoselective, low-density polyethylene film. Soil was fumigated with a 67:33 mixture of methyl bromide:chloropicrin. Precipitation occurred on 14 and 23 days during solarization periods in 1992 and 1993, respectively. Maximum temperatures recorded at depths of 5, 15, and 25 cm were 43.8, 38.9, and 36.5 C in bare soil and 49.5, 46.0, and 41.5 C in solarized soil. Soil solarization resulted in a significant (P less than or equal to 0.05) decrease in the density of Phytophthora nicotianae and P. solanacearum down to a depth of 25 and 15 cm, respectively. Significant reductions in the density of F. o. radicis-lycopersici and F. o. lycopersici following soil solarization occurred only in the upper 5 cm of soil. Fumigation significantly reduced populations of Phytophthora nicotianae, F. o. radicis-lycopersici, and F. o. lycopersici down to a depth of 35 cm. The effect of fumigation on P. solanacearum was highly variable. Additional reductions in the density P. solanacearum were achieved when solarization was combined with fumigation.