Comparative Performance of Fungicides and Biocontrol Products in the Management of Fusarium Wilt of Blackberry

Fusarium wilt of blackberry (FWB) is an emerging disease caused by a Fusarium oxysporum species complex. More than 3,000 ha of blackberry (Rubus spp.) crops have been lost in Mexico since 2011. The objectives of this research were: to evaluate the sensitivity of pathogenic F. oxysporum isolates recovered from symptomatic blackberry plants to fungicides with different modes of action; to assess the potential of these fungicides and plant resistance inducers against FWB in the greenhouse; and to determine the effects of commercial biofungicides and two indigenous strains of Trichoderma spp. on the incidence of FWB. The EC50 values of the fungicides prochloraz, thiabendazole, azoxystrobin, thiophanate-methyl, difenoconazole, triflumizole, and potassium phosphite for six pathogenic F. oxysporum isolates were determined. In a separate experiment, the fungicides acibenzolar-s-methyl (ASM), potassium phosphite, and commercial biofungicides, as well as two soil microbial inoculants and two indigenous Trichoderma strains, were tested for protection against wilt development in blackberry plants in the greenhouse. Prochloraz showed an average sensitivity for EC50 of 0.01 mu g ml(-1) for the tested F. oxysporum isolates, followed by difenoconazole and thiabendazole. Prochloraz and ASM proved to be the most effective treatments in the greenhouse. In contrast, potassium phosphite was ineffective in both the in vitro and in vivo experiments. The soil bioinoculants MicroSoil, Baktillis, T. koningiopsis, and T. asperellum significantly reduced the incidence of disease in the greenhouse. These results provide evidence for the potential of the various tools as useful components of integrated FWB management in the field.