The effects of biological control agents, potassium phosphite and calcium oxide on race 1 of Fusarium oxysporum f. sp. lactucae of lettuce in closed soilless cultivation systems

Eighteen trials were carried out in a closed soilless system to evaluate the effectiveness of different strains of experimental non-pathogenic Fusarium oxysporum and Fusarium solani, commercial biocontrol agents (Streptomyces griseoviridis, Bacillus subtilis and Beauveria bassiana), as well as products based on calcium oxide (CaO) and potassium phosphite on race 1 of Fusarium oxysporum f. sp. lactucae, the causal agent of the Fusarium wilt of lettuce. The treatments were applied to lettuce seedlings, which had been grown for 2 days in a peat medium before being artificially inoculated with the pathogen, and were repeated five times at 7-day intervals. The experimental non-pathogenic F. oxysporum MSA35 and FC3 strains provided a greater disease severity reduction (54%-83% efficacy) than the commercial B. subtilis (29%-31% efficacy), S. griseoviridis (22%-52% efficacy) and B. bassiana (39%-63% efficacy) formulations. The highest fresh weight value was provided by the non-pathogenic F. oxysporum MSA35 and FC3 strains, thereby generally reflecting the observed disease reduction. Calcium oxide and potassium phosphite generally resulted in disease protection, but a great variability in efficacy was observed. The obtained results showed good possibilities for the non-pathogenic Fusarium oxysporum strain against the pathogen in soilless systems.