Soil disinfestation with dimethyl disulfide for management of Fusarium wilt on lettuce in Italy

The efficacy of dimethyl disulfide (DMDS) applied in pre-planting treatment by shank injection was investigated on the lettuce Fusarium oxysporum f.sp. lactucae (FOL) pathosystem in Northern Italy (Piedmont), in three experimental trials. DMDS was tested alone or in combination with metham sodium at 35.9 g/m2, on lettuce cultivars showing different levels of susceptibility to the pathogen. DMDS, at 60 g/m2, reduced FOL symptoms on the highly susceptible butterhead type of 70, 97 and 99%, and of 87, 97 and 100% on the moderately susceptible cultivar, respectively. DMDS at 30 and 40 g/m2 showed a only partial efficacy on both lettuce types used in naturally infested soil, with a disease reduction from 30.3 to 64.5%, significantly comparable with dazomet. The results provided by DMDS at 40 g/m2 plus metham sodium at 35.9 g/m2 were statistically similar to those obtained with DMDS alone at 60 g/m2, and better than those provided by dazomet alone. A positive effect on lettuce yield and weed control by DMDS, at the highest dosage tested and by DMDS plus metham sodium, was also observed.