Assessment of chemical and biosolarization treatments for the control of Macrophomina phaseolina in strawberries

Abstract The phase-out of methyl bromide (MB) in strawberry has increased the difficulty of controlling Macrophomina phaseolina , a soil-borne pathogen and causal agent of charcoal rot disease. In this study, several chemicals and one biosolarization treatment were compared for the control M. phaseolina in three successive seasons between 2009 and 2011. Trials were conducted in two fields with different history of chemical soil treatments in the south-western coast of Spain (Huelva). At Fres-Gomez S.L. farm (Palos de la Frontera), the soil was fumigated with 1,3-dichloropropene:chloropicrin from 2005 to 2008, whereas the soil of Occifresa S.C.A. farm (Moguer), was fumigated with MB until 2001. We determined treatment effects on plant mortality, M. phaseolina population in soil over time, and fruit yield. Five treatments were applied during the 2009–10 season: biosolarization with chicken manure, dazomet + 1,3-dichloropropene, 1,3-dichloropropene:chloropicrin, chloropicrin, and dimethyl disulfide + chloropicrin by shank. During the 2010–11 and 2011–12 seasons, two additional treatments were added: dimethyl disulfide + chloropicrin through drip irrigation and dazomet. An untreated control was also included in all tests. Strawberry cv. ‘Camarosa’ was grown following Spanish standard production practices in high plastic tunnels. Over each season, most treatments reduced M. phaseolina populations in soil 20–100%. However, populations were not significantly reduced by the dimethyl disulfide + chloropicrin applied through drip irrigation. In both farms, treatments reduced plant mortality caused by charcoal rot 35–100% and increased yields 5–56% relative to the untreated control during all three seasons. Economic analyses showed that the cost of treatments was easily offset by increases in yield.