Biocontrol of Fusarium and Verticillium wilt of tomato by Penicillium oxalicum under greenhouse and field conditions

Treatments with conidia of Penicillium oxalicum produced in a solid-state fermentation system were applied at similar densities (6 × 106 spores/g seedbed substrate) to tomato seedbeds in water suspensions (T1 5 days before sowing, or T2 7 days before transplanting; 15 days after sowing), or in mixture with the production substrate (T3 7 days before transplanting; 15 days after sowing). Treatments T2 and T3 significantly (P = 0.05) reduced fusarium wilt of tomato in both greenhouse (artificial inoculation) (33 and 28%, respectively) and field conditions (naturally infested soils) (51 and 72%, respectively), while treatment T1 was efficient only in greenhouse (52%). Verticillium wilt disease reduction was obtained with T3 in two field experiments (56 and 46%, respectively), while T1 and T2 reduced disease only in one field experiment (52% for both T1 and T2). Treatment with conidia of P. oxalicum plus fermentation substrate (T3) resulted in better establishment of a stable and effective population of P. oxalicum in seedbed soil and rhizosphere providing populations of approx. 107 CFU/g soil before transplanting. Results indicate that it will be necessary to apply P. oxalicum at a rate of approx. 106-107 CFU/g in seedbed substrate and rhizosphere before transplanting for effective control of fusarium and verticillium wilt of tomato, and that formulation of P. oxalicum has a substantial influence on its efficacy.