Evaluation of biosolarization for the control of charcoal rot disease (Macrophomina phaseolina) in strawberry

Macrophomina phaseolina, the causal agent of charcoal rot, is a primarily soil-borne pathogen. Charcoal rot has become increasingly troublesome in strawberry (Fragaria × ananassa Duch.) in Spain, where it was reported for the first time in 2006, and worldwide. After the phase out of methyl bromide, some authors have associated the changes in the fumigation products used and methods of applying them prior to planting strawberries with the establishment of M. phaseolina. Moreover, in developed countries, the majority of useful chemical alternatives are futureless, because of regulatory restrictions. Among the non-chemical alternatives for strawberry fruit production is soil biosolarization, a new technique that combines soil biofumigation and soil solarization. In this study, we compared the efficacy of several biosolarization treatments to control M. phaseolina for three successive seasons in a non-chemical treated field near Moguer, Huelva (southwestern Spain). The influence of these treatments on M. phaseolina soil population, charcoal rot development, and strawberry yield was assessed each year. Soil was biofumigated by amendment of fresh chicken manure at 12,500 kg/ha with or without Trichoderma spp (TUSAL®) at 3.5 kg/ha; fresh chicken manure at 25,000 kg/ha; Brassica spp. pellets (BIOFENCE®) at 2000 kg/ha and 15,000 kg/ha; dried olive pomace at 12,500 kg/ha or sugar beet vinasse at 15,000 kg/ha. Soil was then solarized for 30 days by covering with a clear plastic mulch. A control that received fermented manure remained uncovered. The treatments reduced or stabilized M. phaseolina sclerotia populations in soil compared to the untreated control. Treatments which combined biosolarization with chicken manure at 25,000 kg/ha or sugar beet vinasse at 15,000 kg/ha significantly reduced the incidence of charcoal rot compared to the untreated control. Furthermore, yields obtained by amendment with fresh chicken manure (59,319-89,421 kg/ha) were also similar to the yields previously reported for the standard chemical fumigation with 1,3-dichloropropene:chloropicrin. Therefore, biosolarization with fresh chicken manure could be a promising and sustainable option for strawberry crops grown in warm temperate climate areas.