Soil solarization as a sustainable solution to control tomato Pseudomonads infections in greenhouses

Abstract

The reduction or phase-out of soil fumigants according to European directives has led to a re-evaluation of sustainable heat-based techniques and exploiting solar energy, e.g., solarization that was used successfully for the eradication of fungi, weeds, and nematodes. Since the beginning of the current century, bacterial infections caused by phytopathogenic Pseudomonads have been increasingly reported as threat for many horticultural crops worldwide. Nowadays, this disease represents a limiting factor for the tomato production in the Mediterranean basin under greenhouse conditions. Therefore, we tested the effects of soil solarization in controlling natural infections caused by Pseudomonas fluorescens on tomato cultivations in Sicily (south Italy) from 2010 to 2013 under different greenhouse conditions, i.e., with lateral openings uncovered or kept closed. Four experiments were performed under both wooden-concrete and steel-made greenhouses to compare the performances of innovative and traditional films alone or combined with other control measures (only in partially opened greenhouses) against tomato bacterial infections. All solarization treatments were effective in controlling phytopathogenic pseudomonads except for one carried out in a multi-span steel greenhouse with the side openings kept raised. Tested greenhouse covering and mulching films increased soil temperature up to 9.6 °C at 15 cm and 7.7 °C at 30 cm, respectively, if compared to bare plots. Moreover, solarization treatments proved effective in controlling bacterial infections (up to about 90% reduction of disease amount) and in increasing yield up to 45% relative to the bare plots. Among tested films, EVA showed the best performances both in reducing bacterial infections and increasing tomato yield, innovative polyamide VIF and smoky gray were very promising films while green coextruded could be considered a very attractive film since it can be left on after solarization process as mulch for tomato transplanting. This study shows for the first time the feasibility and sustainability of soil solarization performed with innovative materials in managing tomato bacterial diseases in greenhouse.