EFFECTS OF TRICHODERMA AND SOIL SOLARIZATION ON PHYTOPHTHORA CACTORUM IN STRAWBERRY FIELDS

Trichoderma and soil solarization, alone and combined, were tested in three consecutive annual production cycles in Huelva (SW Spain) to evaluate the effectiveness in reducing Phytophthora cactorum soil populations and consequently leather rot on fruit of strawberry plants. Solarization was conducted during the summer, using clear 50 μm low-density polyethylene mulch. Trichoderma spp. were applied via drip irrigation and dip, adding to the soil 7-days before planting (10⁸ conidia/m²), and strawberry roots were dipped in a suspension of Trichoderma (10⁶ conidia/ml) prior to planting. Plots were naturally infested by P. cactorum and had never been treated with methyl bromide. Solarization reduced the soil P. cactorum population 100% in the first year, 47% in the second year, and 55% in the third year relative to the untreated control. Trichoderma spp. aplications reduced soil populations of P. cactorum and reduced leather rot incidence 76.6% in the first year and 33.8% in the second year compared with the untreated control. The combination of solarization and Trichoderma spp. reduced P. cactorum soil population the most each year. The effect of Trichoderma spp. and solarization against P. cactorum indicates that there may be future alternatives to traditional chemicals for disease control.