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Effect of chemical, biological fungicides and resistance inducers for the management of blackberry wilt caused by Fusarium oxysporum

Angel Rebollar-Alviter: Univ Autonoma Chapingo

<div>Blackberry wilt caused by <em>Fusarium oxysporum</em> is one of the most important diseases of blackberry in Mexico causing severe losses on established and new plantings. The objective of this study was to evaluate the effect of chemical and biological fungicides and resistance inducers for blackberry wilt management under greenhouse conditions. First, the efficacy of the fungicides prochloraz, thiabendazole, azoxystrobin, thiophanate-methyl, difenoconazole, triflumizole and potassium phosphite to control six pathogenic <em>F. oxysporum</em> isolates was conducted using an <em>in vitro </em>assay. This was followed by a greenhouse trial to test the same fungicides applied pre-inoculation on 5-month old potted plants. In a separate experiment, the effect of commercial biocontrol agents, including a strain of <em>Trichoderma koningiopsis</em> (RCH-169), and resistance inducers (potassium phosphite and acibenzolar-s-methyl) was quantified. Incidence, severity, fresh weight, dry weight, root length, plant height, and colony forming units (CFU g<sup>-1</sup> of soil) were obtained. Under <em>in vitro</em> conditions, Prochloraz showed the strongest inhibitory effect (EC<sub>50</sub>=0.01 μg mL<sup>-1</sup>), followed by triflumizole (EC<sub>50</sub>=0.05-0.32 μg mL<sup>-1</sup>) and difenoconazole (EC<sub>50</sub>=0.09-0.13). In greenhouse experiments, prochloraz and acibenzolar-S-methyl were most effective in reducing the incidence and severity of blackberry wilt. In the biological control trial, the native strain of <em>T. koningiopsis</em> resulted in the lowest incidence (33%) and severity (28.43%), compared with commercial products and the control, including higher fresh weight and lower number of CFU g<sup>-1</sup> soil. Together these results indicate some promising treatments for the control of blackberry wilt, which could be integrated into a full season approach to managing the disease in the field.</div>