Efficacy of Biosolarization with Sugar Beet Vinasses for Soil Disinfestation in Pepper Greenhouses

In region of Murcia (Southeast Spain), sweet pepper is a monoculture. Phytophthora spp. and Meloidogyne incognita are the main soilborne pathogens. Methyl bromide (MB) has been used as a common soil disinfestant during 20 years until its banning in 2005. Disinfestant efficacy of biosolarization with sugar beet vinasse at doses from 0.75 to 1.5 L m(-2) alone or mixed with fresh sheep manure has been evaluated in several experimental greenhouses. When biosolarization was initiated in August, the survival of P. capsici oospores was very low and similar to MB; M. incognita control was better when sugar beet vinasse was mixed with fresh sheep manure (Nodulation Index (NI)=0.7; percentage of infested plants (IP)=20%) in relation to the fresh sheep manure alone (NI=1.5; IP=40%), with no difference in relation to vinasse alone (NI=1.2; IP=35%) and improving the effect of MB (NI=2.8; IP=48%) or the control (NI=5.6; IP=86.7%). Pepper yield in biosolarization treatments was similar to MB (13.1 kg m(-2)). Results showed that when biosolarization treatments are carried out in October, disinfectant efficacy decreases, since the incidence of Phytophthora and Meloidogyne increased using either sugar beet vinasses alone or mixed with fresh sheep manure.