Effect of solarization on the control of Phytophthora cambivora in almond and cherry

Abstract

Solarisation, the technique of heating soil to 8- 10¦C above ambient temperatures by covering the soil with transparent plastic sheeting, was evaluated as a means of controlling Phytophthora cambivora in naturally infested almond and cherry orchards. Laboratory experiments showed that a 6-h exposure to 45¦C was lethal to mycelial growth and inhibitory to the production of sporangia of P. cambivora, whereas several periods of exposure at 35 and 40¦C were necessary to inhibit the fungus to the same degree. In field experiments, soil temperatures greater than 40¦C were rarely recorded at a depth of 10 cm in solarised soil, yet the treatment controlled P. cambivora infection in an irrigated cherry (cv. Mahaleb) orchard for more than 12 months. However, solarisation was not effective in non-irrigated almond (cv. Mission) orchards, and the possible reasons for this are discussed.Solarisation had no effect on established infections of P. cambivora but growth of plants in solarised areas was significantly greater than that of plants in untreated or metalaxyl treated areas.