Abstract

The effectiveness of alginate solid formulations of Trichoderma harzianum containing either Th12.A.10.1 or ThF2-1 for the biocontrol of Pyrenochaeta lycopersici was compared to that of methyl bromide (60g.m(-2), five days of soil exposure) and to that of the commercial biofungicide, Trichonativa (R), in a commercial tomato crop grown under greenhouse conditions. A single application of any of the solid formulations at 1.7g-l(-1) soil (8.5-11.9x10(5) CFU/plant) or of 5ml.l(-1) soil (5x10(9) CFU/plant) of Trichonativa immediately before tomato transplantation did not prevent tomato root damage. The formulation containing ThF2-1 was the only that allowed the reduction of the root damage level caused by P. lycopersici from 1.6 to 0.2 (Campbell and Shiskoff scale), when applied immediately before transplantation, 15 days after transplanting and one week before sprouting. This effect was coincident with a higher persistence (t(0.5)= 4.7 months) than that of Thl2A.10.1 (2.7 months) or to that of the liquid commercial product (0.7 month), suggesting that solid formulations maintain integrity of Trichoderma strains in the soil, which appears to be an important factor to prevent corky root of tomato. In addition, persistence of ThF2-1 in the soil after three applications of the solid formulation supports its use for the control of P. lycopersici, being an adequate alternative strategy to the application of methyl bromide in commercial tomato crops.